This is the multi-page printable view of this section. Click here to print.

Return to the regular view of this page.

MCH2022 badge

MCH2022 badge

The MCH2022 badge is our most advanced badge yet. Shaped like a game console this badge is a powerhouse filled with cool technology.

Once assembled, you can use the badge to display your name, write Python code and maybe play a game or find an Easter Egg, but don’t forget: the real fun starts when you hack it to make it your own!

MCH2022 badge overview

Getting Started

We’ve assembled some resources to quickly get started.

Getting Help (and helping …)

Reread the instructions if something isn’t working. Then go to our Troubleshooting Guide

Check out these resources if you run into trouble.

Case and frontpanel

You can find a 3D printable case and a lasercuttable frontpanel in this GIT repository.

The Hardware

The badge contains an Espressif ESP32 Wrover-e WiFi module with 16MB of flash storage and 8MB of PSRAM, an Raspberry Pi RP2040 microcontroller chip for advanced USB communication and board management and a Lattice ICE40UP5K FPGA for hardware accelerated graphics.

It also contains a bunch of stuff (TODO elaborate “stuff”).

The hardware is described in more detail in the hardware section.

The Software

The ESP32 loads an application chooser menu when you first power it on. Once loaded, you can launch a number of preinstalled applications:

  • the Name-Tag app
  • a Micropython scripting environment
  • a sensor playground for the Bosch sensors
  • The Hatchery where you can load more apps!

and the app contains a link to the Hatchery an app store you can use to load more apps. And more importantly, where you can publish app you write yourself.

The software is still in active development, more information will be published here soon.

Hardware sponsors


  • ALLNET China was our production partner, for which we are more than grateful. They took care of sourcing most components and oversaw the production process in China, saving us a lot of work and potential headaches and allowing us to focus on the product!
  • Espressif was very generous to donate us all of the ESP32-WROVER-E modules we needed. The ESP32 has proven itself to be a solid basis for badges in the past, and for related projects such as the PocketSprite. Espressifs continued support means a lot to us as it allows us to continue expanding our existing ESP32-based ecosystem!
  • Lattice Semiconductor provided us with 4000 pieces of their awesome ICE40UP5K low-power FPGA. With this donation, they enabled us to explore and provide a new dimension of hardware capabilities and user-created applications. We shipped the first FPGA-equipped event badge in the world. Thanks Lattice!
  • Bosch Sensortec let us put two of their advanced sensors on the badge: the BNO055 9-axis Absolute Orientation Sensor, and their new BME680 Air-Quality (And More) Sensor. These sensors enable a range of uses for the badge off-the-shelf, allowing developers to develop more engaging games and expanding the range of potential uses for the badge after the event.
  • The Raspberry Pi Foundation helped us out with a discount when another chip which we tried to source became unavailable. On the badge, the RP2040 enables a wide range of USB capabilities, allowing us to work on bridging the gap between embedded development and everyday computing.

All of our sponsors helped us out in a time when sourcing capable chips was a near-impossible task. Without them, this project would not have been possible. We are grateful to all of them for their help and sponsorship, and we hope to work with them again in future badge projects!

The team

The MCH2022 badge would not have been possible without the help of these amazing volunteers.


  • Reinier van der Leer


With the help of Anne Jan Brouwer, Kliment Yanev, Kuristian, Martin Ling, Paul Honig, Sylvain Munaut, Tom Clement, Fuchsia (f0x) and Sander de Haan.

Launcher firmware

FPGA examples and tools


RP2040 co-processor firmware

  • Renze Nicolai
  • Sylvain “tnt” Munaut
  • Reinier van der Leer (Pwuts)
  • Jana Marie Hemsing


  • Tim Becker (a2800276)
  • Matthias Koch (Mecrisp)
  • Pepijn de Vos
  • Julian Scheffers (Robotman2412)
  • Sylvain “tnt” Munaut
  • TheRealProcyon
  • Pieter Vander Vennet
  • Jenny List
  • Oskar Roesler (bionade24)
  • Dominik (dloidolt)
  • Manuel Dipolt (xeniter)
  • p2mate
  • Sietse Ringers
  • Yvo de Haas
  • Marble (cyber-murmel)

1 - MCH2022 Badge Hardware

Block diagram

The badge contains a huge amount of awesome chips, so many that a block diagram is necessary to explain how everything is interconnected.

Block diagram

The ESP32 is at the center of the operation. It has access to almost all the peripherals on the badge and using its WiFi connectivity it can load new firmware and applications from the internet.

The RP2040 microcontroller provides USB connectivity consisting of two serial ports (for the ESP32 and the FPGA), WebUSB for managing the badge using your browser and HID for acting like a keyboard, mouse or joystick. It also drives the SK6812-EC15 addressable LEDs, giving the badge a lot of bling and eyecandy. To top it off a lot of the I/O pins of the RP2040 have been broken out, both as the IO pins of the SAO connector and as testpads next to the prototyping areas on the back of the badge.

The ICE40UP5K FPGA is programmed over an SPI connection by the ESP32. Using this connection the FPGA can also communicate with the application running on the ESP32. Our goal is to enable people to learn about HDL programming so new bitstreams can easily be loaded into the FPGA by user applications, to provide any function you want ranging from a simple LED blinker to a RISC-V SoC. To accomodate more advanced designs the FPGA is connected to the LCD display via a parallel bus, enabling it to update the display at high refresh rates, as well as 8MB of PSRAM via a Quad-SPI bus. 8 of the I/O pins of the FPGA have been broken out as an industry standard PMOD header, allowing users to connect standard expansion modules or their own creations.


Datasheets and Resources

  • ESP32 datasheet the datasheet for the main processor
  • ESP32 technical reference technical reference for the main processor. This contains information about the features of the chip, so technically, it belongs in the firmware section, but … whatever.
  • WROVER datasheet datasheet of the module. The processor is packed together with peripherals necessary for operations in a module (WROVER) nuder a metallic can.
  • RP2040 documentation site and datasheet
  • Lattice ICE40UP5K - iCE40UltraPlus documentation site and datasheet
  • BME680 4 in 1 gas sensor. (temperature, humidity, air pressure and volatile organic compounds (VOC)
  • BNO055 accelerometer, gyroscope, magnetometer sensor
  • Display also have a look here
  • SK6812-EC15 addressable RGB - LEDs (aka Neopixel)
  • MS4344 Audio DAC

1.1 - MCH2022 badge pinouts


SAO (Shitty AddOn)

Addon connector following the SHITTY ADD-ON V1.69BIS standard.

1VCCPower output3.3v supply voltage output
2GNDPower outputGround reference
3SDAData IOI2C bus data
4SCLData outputI2C bus clock
5GPIO1Data IOUser configurable IO, connected to RP2040 GPIO18
6GPIO2Data IOUser configurable IO, connected to RP2040 GPIO19

PMOD (peripheral module interface)


The PMOD connector is wired up to the iCE40 FPGA. Note that while the connector is physically located on the backside of the badge, it has been wired up such that the PMOD’s top side must be pointed in the same direction as the badge’s top.

PMOD pinICE40 pinNote
147IOB_2a (paired with PMOD pin 7 IOB_3b_G6)
248IOB_4a (paired with PMOD pin 8 IOB_5b)
34IOB_8a (paired with PMOD pin 9 IOB_9b)
744IOB_3b_G6 (paired with PMOD pin 1 IOB_2a)
845IOB_5b (paired with PMOD pin 2 IOB_4a)
93IOB_9b (paired with PMOD pin 3 IOB_8a)



ESP32 GPIODirectionFunctionNote
0BothI2S master clock output / UART download select inputDrives I2S DAC / driven by RP2040 through resistor
1OutputUART TXConnected to RP2040
2BothSD card data 0SD card slot
3InputUART RXConnected to RP2040
4OutputI2S bit clock
5OutputLED dataConnected to the SK6805 LEDs in the kite
12OutputI2S LR channel select
13OutputI2S data
14OutputSD clockSD card slot
15OutputSD commandSD card slot
18OutputSPI clockConnected to LCD and FPGA
19OutputSD card and kite LED power controlSet high to enable power to LEDs and SD card
21OutputI2C clockConnected to RP2040, BNO055, BME680, Qwiic connector and SAO addon connector
22BothI2C dataConnected to RP2040, BNO055, BME680, Qwiic connector and SAO addon connector
23OutputSPI MOSIData from ESP32 to LCD / FPGA
25BothLCD resetSet to output low to reset LCD, leave floating normally
26OutputLCD modeLow: LCD in SPI mode, high: LCD in parallel mode
27OutputSPI chip select for ICE40Low: select ICE40, high: deselect ICE40
32BothSPI chip select for LCDLow: select LCD, high: deselect LCD. Note: output in LCD SPI mode, input in LCD parallel mode
33BothLCD DC (data or command) selectionNote: output in LCD SPI mode, input in LCD parallel mode
34InputInterrupt from RP2040
35InputSPI MISOConnected to ICE40
36 (SENSOR_VP)InputInterrupt from position sensor (BNO055)
39 (SENSOR_VN)InputInterrupt from ICE40 FPGA


RP2040 GPIODirectionPullFunctionDescription
2BothI2C1 SDAI2C bus data (RP2040 is in slave mode)
3InputI2C1 SCLI2C bus clock
4InputUpGPIOButton: MENU
5InputUpGPIOButton: HOME
6InputUpGPIOButton: ACCEPT
7InputUpGPIOButton: Joystick A
8InputUpGPIOButton: Joystick B
9InputUpGPIOButton: Joystick C
10InputUpGPIOButton: Joystick D
11InputUpGPIOButton: Joystick E
12BothGPIOESP32 bootloader mode¹
13OutputGPIOESP32 enable
14BothGPIOESP32 interrupt¹
15OutputPWMLCD backlight brightness
16BothGPIOAvailable next to prototyping area
17BothGPIOAvailable next to prototyping area
20InputGPIOFPGA done
21OutputGPIOFPGA reset
22InputUpGPIOButton: START
23InputGPIOLiPo charger state
26InputUpGPIOButton: BACK
27OutputGPIOInfrared LED
28InputADCVoltage measurement: USB input
29InputADCVoltage measurement: Battery

¹: Set to input normally and force low to activate


ICE40 pinICE40 GPIODirectionDescriptionNotes
2IOB_6aBothPMOD pin 4
3IOB_8aBothPMOD pin 3
4IOB_9bBothPMOD pin 9
6IOB_13bInputUART RX
9IOB_16aOutputUART TX
11IOB_20aOutputLCD register select
12IOB_22bBothRAM SPI D2
13IOB_24aBothRAM SPI D1
18IOB_31bOutputRAM SPI CS
19IOB_29bOutputRAM SPI SCK
20IOB_25b_G3BothRAM SPI D3
21IOB_23bBothRAM SPI D0
23IOT_37aOutputLCD write
25IOT_36bInputLCD frame sync
26IOT_39aOutputLCD data 0
27IOT_38aOutputLCD data 1
28IOT_41aOutputLCD CS
31IOT_42bOutputLCD data 2
32IOT_43aOutputLCD data 3
34IOT_44bOutputLCD data 4
35IOT_46b_G0Input12MHz clock
36IOT_48bOutputLCD resetActive-low, drive open-drain
37IOT_45a_G1OutputLCD data 5
38IOT_50bOutputLCD data 6
42IOT_51aOutputLCD data 7
43IOT_49aInputLCD modeShould be driven by ESP and monitored by FPGA
44IOB_3b_G6BothPMOD pin 7
45IOB_5bBothPMOD pin 8
46IOB_0aBothPMOD pin 10
47IOB_2aBothPMOD pin 1
48IOB_4aBothPMOD pin 2

1.2 - MCH2022 Badge Hardware Hacking

The badge is made for hacking, and the hardware is no exception. There are several intended ways to extend the badge, next to unlimited unintented ones.

If you have access to a 3D printer, an easy and worthwile hardware mod is to print a knob for the joystick, such as this one or a case.

Shitty Add-on

The badge has a SAO header, which can provide power, I2C, and 2 GPIOs to small accessories that can be plugged in.


At the back of the badge there is a Qwiic connector hooked up to the ESP32 that is compatible with a large family of modules from Sparkfun, Adafruit and others.


On the side of the badge there is a PMOD connector hooked up to the FPGA that is compatible with a large family of modules from Digilent and others.

May Contain Hardware Area

On the back of the badge there is a prototyping area with a grid of pads, as well as pads the expose I2C, power, and GPIOs.

Across the rest of the PCB are labeled pads that expose things like the LED serial data, audio signal, IR signal, various debug pads, and more.

2 - Getting Help (and helping)

You’re on the main documentation site for The Badge.

We hope that we’ll be able to centralize all documentation efforts here, but who knows what happens at camps.

We would be very happy to accept pull request (TODO link to how to make a good PR) if you find the documentation lacking and feel you are able to make improvements. The documentation project lives in this github repository

If you feel your Badge is broken, go HERE first!

Random Resources for Getting Help

But I want to chat with somebody …

And if you’re reading this at MCH2022, just come by our tent

Overview of the main github Repos you can contribute to …

You can find the sources and hardware files for all Badge artefacts files under the organization:

Non-Specific Resources


  • reddit/r/esp32
  • rp2040 (todo)
  • micropython
  • lattice
  • yosys fpga getting started general

2.1 - Troubleshooting & FAQ

This page is intended to collect answers to questions that pop up frequently and solutions to common problems…

MicroPython crashes every time I connect to it …

Apparently I’m disturbing the Guru’s Meditation

In case you are trying some Python samples and the firmware crashes … like this:

Guru Meditation Error: Core  0 panic'ed (Interrupt wdt timeout on CPU0).

Core  0 register dump:
PC      : 0x40084b56  PS      : 0x00050035  A0      : 0x400d7fde  A1      : 0x3ffbe990
A2      : 0x00040040  A3      : 0x3ffb27e0  A4      : 0xc0000000  A5      : 0x3ffbe970
A6      : 0x3ff40000  A7      : 0x3ffbf074  A8      : 0x800d7fde  A9      : 0x40090908
A10     : 0x00000000  A11     : 0xa6000000  A12     : 0x00000000  A13     : 0x00000473
A14     : 0x3f403a98  A15     : 0xffffffff  SAR     : 0x0000001f  EXCCAUSE: 0x00000005
EXCVADDR: 0x00000000  LBEG    : 0x4000c2e0  LEND    : 0x4000c2f6  LCOUNT  : 0xffffffff
Core  0 was running in ISR context:
EPC1    : 0x400d3f03  EPC2    : 0x400d7fde  EPC3    : 0x00000000  EPC4    : 0x00000000

Backtrace:0x40084b53:0x3ffbe9900x400d7fdb:0x3ffb27e0 0x401d505f:0x3ffb2800

We are working on it:

  • make sure you’ve updated your BadgePython to the newest version. Use the AppUpdate menu item…
  • try deleting Python from the Apps menu and reinstalling it from The Hatchery (Hatchery->ESP32->Utilities)

If none of this helps, here’s an easy work around … Connect to the serial console before you start Python. While you’re still in the launcher, connect, you will see some of the logging of the launcher application, when you start Python, you will see the boot messages. If the serial console is already attached when Python starts, it doesn’t crash. WTF!? ¯\_ (ツ)_/¯

I keep getting 419 errors in the Hatchery!

If you can’t log in to the Hatchery (or create an account) or whatever because you are getting 419 Expired errors, you need to either clear all cookies for the Hatchery, use incognito mode to connect or try a different browser. Please also report your experience, inlcuding time of occurance in the issue concerning this behavior to help figure this out.

My SD-Card is not being recognized

Try formatting the card as FAT32. Unfortunately exFAT is currently not supported.

The wifi doesn’t work!

Your battery is probably too close to the ESP32 “tin can”. Try moving it over :) The black strip on top of the can is the wifi antenna, you need to make sure that bit is not covered by anything.

Move battery in this direction

The kite in the front is flashing RED!? Am I in danger!?

You’re probably fine. But be sure to drink plenty of water. But you will need to:

  • Download the the RP2040 coprocessor firmware U2F
  • Turn the Badge off ( with the switch labeled ON-OFF)
  • Hold the SELECT button while turning the switch back to ON
  • Make sure a USB cable is connected to your computer
  • The Badge will mount as a mass storage device (MSD, a.k.a USB thumbdrive)
  • Drag-n-drop (or whatever it is you Linux-from-Scratch folks do …) the U2F firmware onto the drive

This sounds way more complicated than it is, you’ll figure it out. In case you don’t that means we msessed up something else as well, please bring your Badge to the Badge tent so we can have a look to see what went wrong.

The badge doesn’t connect to the computer

If you have followed the instructions concerning udev rules, you may have a bad USB cable. Or a charging only cable. Did you make sure to connect one end of the cable into the computer and the other into The Badge? Try running lsusb, it should contain an entry like the one below:

$ lsusb
Bus 002 Device 025: ID 16d0:0f9a MCS MCH2022 badge

If instead, you see a line like this:

Bus 002 Device 027: ID 2e8a:0003 Raspberry Pi RP2 Boot

You may be having some issues with the Bootloader, have a look here for some hints.

Try running lsusb without a badge and see if you get different messages when a Badge is connected.

If this is not the case, try out a friend’s cable.

Button presses are glitching/bouncing‽

Your badge is probably not broken. Try updating the OS first. Choose “OS Update” in the main menu.


In case you see this when first booting your Badge:

OMG, Fail!?

Don’t worry, that just means one of the elves in Santa’s workshop forgot to confirm that the self-test passed. Plug it into USB, and press A.

3 - Getting started

Congratulations, you’re the proud owner of a shiny new MCH badge! It’s a fully-functional computer, and while you (can do stuff with it) out of the box, the real fun starts when you start hacking it. The badge has two processors, an FPGA and a ton of sensors and toys to play with all in the palm of your hand! And we’ve done what we could to make using it as friendly and intuitive as possible. We had a lot of fun making it, and we hope you’ll have a lot of fun using it.

No fluff! I wanna get started!

Hook up the battery to the badge, the connector only allows it to be connected the right way around. Set the labeled on/off switch to ON. Things should quickly start up, display works and it makes a sound.

If this is the case everything works and you’re good to go. Attach the battery to the badge using the included velcro, slap on the lanyard (and possibly insert an SD-Card) and Start Hacking!

Don’t forget to update the OS and preinstalled apps. And have a look at some general tips for Using the Badge.

The rest of this page contains more detailed instructions in case you run into problems.

In the pack

Picture of contents of pack

If you are reading this at MCH, you received the unassembled badge in a bag when you entered the camp. Inside the bag are the following items:

(These will obviously change subject to what is in the pack)

  • The badge itself
  • A lithium-polymer battery for the badge
  • A self-adhesive Velcro patch for attaching the battery
  • A printed badge lanyard
  • A leaflet containing basic information about the badge

Fitting the battery


The battery is a silver pouch with a short cable terminated in a trailing socket connector. This mates with a PCB mounted plug which you’ll find on the component side of the badge. Place your badge screen side down with the USB-C connector facing towards you, and you’ll find the on-board battery connector at the bottom right next to a field of gold squares (the prototyping area -> link to hardware).


The trailing plug on the battery has a small lug on one side that interfaces with a notch in the on-board socket. With the lug facing upwards, carefully slot the two connectors together.

Now turn the badge on. The switch is labeled ON OFF and located just below the battery connector. It will boot up, the display will start displaying things and the speaker will make some noise.

The battery should now be attached to the badge via the connector. We’ve provided velcro so you can affix it to the badge more firmly. One side of the battery tends to buldge, so try out which side lies most snugly against the badge. Find a good spot on the back of the battery and the reverse of the badge to attach the velcro.

Inserting an SD-Card

The SD-Card holder is a bit fiddly. We’ve assembled an illustrated guide to inserting an SD-Card.

Now what?

You should now have a working badge. We strongly suggest that you hook it up to a live USB power source to fully charge the battery. You’ll need a cable with a USB-C at the Badge end.

While the battery is charging, it’s time to explore the badge a little. When you turn it on it will start with a splash screen and details of all the sponsors who have made the event and the badge possible. You’ll then see the badge menu screen, so now’s a good time to move along to the next step in this introduction: using the MCH 2022 badge.

Also, as with all security critical devices, make sure you update the Badge software and any of the apps you installed. There’s a menu item for that, which will probably save you a lot of grief from bugs we’ve already fixed!

3.1 - Inserting an SD Card

I inserted the card correctly, but it doesn’t work.

Format the card as FAT32 not exFAT, please. And if you are using a humongous 12TB Super SD Card, maybe try a cheap, small one from the grocery store :)

Oh Noes! I broke off the little metal thingie of the SD Card holder!

Oh well, better luck next time! Don’t feel bad, you’re not alone.

You can probably stick it back into the little grey plastic thingie.

I almost broke off the little metal thingie of the SD Card holder, WTF!?

Lucky you! You’ve come to the right place.

The trick is to:

  • insert a fingernail into the SD-Cardholder manipulation slot and pull DOWN! (DOWN is in the direction of the arrow in the picture.)

  • Somehow I never realized the metal thingie actually has “OPEN->” embossed in it until I uploaded the picture for the documenation. Don’t I feel stupid …

pull DOWN

  • fiddle around with your SD-Card to somehow get the alignment slot of the grey plastic thingie to align with the alignment notch in the card.

align notch

  • find a small-fingered nerd to hold the SD-Card in place while you flip the metal fastener over the card and insert a fingernail into the SD-Cardholder manipulation slot and push UP! (UP is the direction of the arrow in the picture)

push up

3.2 - Installing Apps from "The Hatchery"

WTF is a Hatchery!?

The Hatchery is an app store for The Badge!

You can also sort through the apps other people have published there. If you do so, please be aware that we don’t check for malware and will NEVER ask for your credit card number or home banking password (just kidding, off course we will.)

BTW, it’s called Hatchery because it (used to) contain “eggs” because previously the Hatchery was limited to Micropython apps and those are called eggs. And eggs hatch if you don’t eat them. Nowadays the Hatchery also supports native ESP Apps and FPGA bitstreams.

You can also use the Hatchery to publish your own apps and share them with friends. And unlike other App Stores, you don’t need a Dunn & Bradstreet Number, $1000 and don’t have to worry about your app being rejected because it contains malware.

A Word of Warning

Our crack team of Useability Experts are working around the clock to make the Hatchery even more intuitive and easy! So some of the information here, especially the screenshots may be out of date by the time you read this. Also, the documentation team is exceptionally lazy. Did we mention you can help update the documentation!? Go to the website project to create a Pull Request!

Better yet, check out the repo for The Hatchery itself and make improvements.

In case you are experiencing issues receiving 419 errors, clear cookies and try again.

Find an App

This will probably be the challenging part. We recommend you do this on a big computer, like a laptop. Something with a keyboard.

Go to and sift through our fine offering of Hello World apps and super slow bitcoin miner malware.

Pick an App

If you go to the apps details page, you can download the app. But you don’t need to. Just remember the Category.

Now, go to the Hatchery app on the Badge.

Hatchery … the app

Next you’ll be asked whether you want to install an ESP32 app, a Python egg or and FPGA bitstream. At the moment you kindof need to guess, here’s a heuristic:

If the details page contains:

  • a file named main.bin it’s ESP32
  • a bunch of Python files, it may be Python
  • a file named bitstream.bin it’s an FPGA bitstream

In the next step, go to the Category remembered. Let’s pick “Safe Credit Card Detail Storage” (ESP->Utility). That sounds totally legit! Select it with the A button and you will see app details. As you can see, the app is, in fact, totally legit.

Totally legit

Now just press A to install. It will download for a while. Once it’s done, go to the “Apps” menu and your brand new app should be available to launch! Or … uninstall.

App Launcher

3.3 - Using Your Badge

Your MCH badge comes with installed software which allows you to select and run applications, install new applications from the online Hatchery, and configure Badge functions such as the Wi-Fi SSID and password (don’t worry, it can connect to camp Wifi out of the box).

This page is a high-level introduction to the installed software. If you came here looking for details on how to write software for the badge, then take a look at our software development guide.

Start at the menu screen

When you first turn on your badge, you’ll see a series of logos of the MCH2022 sponsors (Thanks again!) before finally a chime plays on the speaker and you find yourself at the main menu screen. It’s a graphical launcher with a series of icons for the different Badge functions. You can select a function with the joystick before launching it with the A button or by clicking the joystick.

When you are in an app the convention is that the A button is usually an action, the B button should take you one step back, and the Home button at the bottom left of the screen should take you out of the app and back to the menu.

As shipped, the badge has seven options on the main menu:

  • Name Tag. This is the usual name tag app for an event Badge.
  • Apps. This takes you to the user-installed apps on The Badge, including a Python launcher for backwards compatibility with previous badges going back to the SHA 2017 badge.
  • Hatchery. This is the app store for The Badge. Explore it to find new apps written by other MCH attendees.
  • Tools. Here you can find a file browser, as well as infra-red remote control apps for some of the camp lighting.
  • Settings. This takes you to a selection of badge configuration options. The badge ships pre-configured for the MCH2022 network, however it’s on this menu that you can find the tool to reconfigure it for your home network.
  • App update. This option updates the apps on your badge to their latest versions from the hatchery.
  • OS update. Here you can update the badge firmware.

4 - Software Development

Introduction …

This is a shameless placeholder for the software development section.

There are roughly 3 to 5 ways to develop for the Badge (depending on how you count:)

  • Micropython : write apps in Python! This is the easiest way to get started, with the additional benefit that you probably don’t need to install anything (or much). Actually this should be the easiest way, but unfortunately has the fewest docs. Have a look here for documentation of the Python modules on the Badge.
  • ESP-IDF : native EPS apps using the IDF (IoT Development Framework)
  • FPGA : this is the special feature … not happy with the Tensilica CPU on the ESP? Just implement your own RISC-V core (or, to get started, connect all the buttons together with an AND gate…)

The other two plus (depending on how well you can count) :

  • RP2040: aka Raspberry Pico. This is an onboard conprocessor that we are using as our USB Lifeline to the outside world. As such, if you break stuff here, you can easily brick your badge. Feel free to play around with it, but be aware: THIS VOIDS YOUR WARRANTY … and not in a fun way. It’s very unlikely we’ll have the resource to help you fix the badge during the camp.
  • RISC-V and Forth: Because the badge contains an FPGA, you can turn it into anything you want. Technically the RISC-V and Forth projects are just FPGA projects, but the RISC-V CPU is powerful enough to run a Mandelbrot and Tricorn fractal explorer. A different RISC-V processor implementation with a focus on performance instead of readability can even run Doom! The Forth includes a custom stack processor and besides being useful for interactice experiments with freshly soldered additions on the PMOD connector, it can run a game of Snake.
  • Rust: just a hint or two to get you started. Ask around the Telegram channel if you need support.
  • TinyGo: Some hints on getting started with TinyGo on the Badge and some samples …
  • Arduino: this was intended to be done and beautifully polished … but then we all got COVID and couldn’t finish. You can try to develop apps with Arduino if you think it will be easier, but it will probably cause some pain. Of course, we would be ecstatic if you help getting it work smoothly.

Linux permissions

Regardless of the way you’re going to program the badge, to connect to the badge over USB from Linux, do the following.

Create /etc/udev/rules.d/99-mch2022.rules with the following contents:

SUBSYSTEM=="usb", ATTR{idVendor}=="16d0", ATTR{idProduct}=="0f9a", MODE="0666"

Then run the following commands to apply the new rule:

sudo udevadm control --reload-rules
sudo udevadm trigger

Windows installation

To upload programs to the badge with the provided tools, python and pyusb are needed. The easiest way to install these on windows is by installing miniconda

After installation, open “Anaconda prompt” from the start menu. Then do the following

conda create -n badge -c conda-forge python pyusb
conda activate badge

Now you should be able to run commands like:

python ".\Desktop\mch2022-tools-master\" .\Desktop\ /flash/apps/python/button_tester/


The Badge comes with a preinstalled Micropython interpreter. Python should be the easiest way to control the device and the easiest mode to write apps for The Badge, especially if you are a beginner or don’t want to spend a lot of time downloading toolchains and debugging drivers.

Before the Camp and if you are afraid to break things…

Uri Shaked a.k.a Wokwi built an awesome emulation of the badge that runs in your browser. You can use it to test stuff out if you don’t yet have a Badge or your Badge is being used for something else. Or if you just feel more comfortable with a Badge that can’t catch on fire. It fantastic, you can click the buttons and everything! Try it.

Wokwi Badge Emulator

On the device!

First, make sure Python is installed and that you didn’t accidentally delete it. Check in the apps menu. If it’s not there: install the Python app from the Hatchery by going to Hatchery -> ESP32 native binaries -> Utility -> Python and install it either onto the flash or onto an SD card.

This badge contains a common ESP32 firmware platform shared with other badges, so to learn more about the general platform and its components, start here. In addition there is also a mch22 module that offers a few badge-specific APIs.

While the above allows you to access the Python shell and install Python apps from the hatchery, here is how you upload custom apps to the badge over USB:

  1. Download mch2022-tools
  2. Write you Python code using the platform modules documented above
  3. Use python3 /sdcard/apps/python/myapp/
  4. Start your app in the Apps menu.

There’s a more detailled description on Micropython development here.

4.1 - Developing native Badge apps with the ESP-IDF


Even though MicroPython is a quick and easy way to write apps for the Badge, you are limited both in terms of performance and functionality. If you need or want to write native applications, you have found the right place. This section describes how to develop Badge apps using the ESP-IDF, the development toolchain for native ESP32 apps.

Should I write a native app?

TLDR: OF COURSE YOU SHOULD! It’s fun! Hey, this Badge is for an event called “May Contain Hackers”, it was made for hacking in every possible way!

Native apps are amazing. The beautiful sponsors slideshow that you saw when you first booted your Badge was a native app. The BadgePython interpreter that runs all the BadgePython Eggs is a native app. Native apps are not launched within the Badge firmware - they are directly mapped to memory and then the Badge is rebooted. In other words: No walls, no fences around you. Ideally suited for writing Badge malware! Your code runs directly on the metal. This makes native apps the perfect option if you need full power and/or full access to all the MCU’s peripherals, not just the ones with a Python wrapper.

However, this comes at a (small) price: As native apps need to be directly accessible to the ESP32, their binaries reside in a special partition in the module’s internal Flash memory (if you’re interested in the magic behind it, have a look at the AppFS component). Because they are standalone firmwares, they tend to be larger than simple MicroPython apps. As a consequence, there is a limit to how many native apps can be installed on a Badge (five-to-ten-ish, depending on code size). If you run out of memory, you will have to uninstall others.

Getting Started

If you want to dive right in, here’s a short example walktrough to quickly get started writing a native ESP-IDF app.

Template App

The template app is a public template repository to use as a basis for your own app. It contains an application skeleton, an appropriate version of the ESP IDF and components for common Badge peripherals. You can find the template app on github. All examples here use this template. Basically: Clone, build, install, publish, fun. Incidentally, the template app has a button you can use to create a clone for your github user.

“Use this template” Button

A More Advanced Example

Once you are familiar with the template and getting started example, it’s time to move a step further. The ESP-IDF has tons of features to offer. Here’s a more advanced app which turns your badge into a (crappy) bluetooth speaker.

4.1.1 - ESP-IDF getting started

Programming native applications on the Badge requires an ESP IDF to be installed. IDF stands for “IoT Development Framework” and is Expressif’s SDK which provides:

  • convenient access to hardware functionality
  • implementation of protocols such as TLS, HTTP and MQTT which are commonly used in IoT projects
  • common utilities such as logging, error handling and JSON parsing
  • infrastructure code for building, flashing and debugging.

The IDF will be installed automatically (via git submodules and make commands which we will point out) but it does require some dependencies to be installed.

Installing Prerequisites

How to install these prerequisites is described on the IDF documenttion page for:

The instructions will (mainly) install git, cmake and python. Remember you DO NOT have to install the IDF!

In order to sideload the apps you develop, you will be using our webusb tools. These tools will get automatically installed, but require pyusb to be installed. This can be installed with pip install pyusb or apt install python3-usb

Download & build the “template app”

We created a basic Hello World template app that’s intended to be used as a basis for native badge apps you build. To allow you to get started quickly, the template app downloads the IDF in the required version, as well as some badge specific components you will.

To clone the template app, open a shell:

$ git clone my_fancy_app_name
$ cd my_fancy_app_name

The Makefile in the template app contains a number of targets for your convenience:

  • prepare : Download all the ESP32 dependencies needed to build, you only need to run this once!
  • build : compile the code
  • install : install the app you just compiled (NOTE: if you have previously used the IDF to build ESP32 code, this is different from regular flashing! see below)
  • monitor : connect to the ESP32 console and look at your log files.
$ make prepare # this downloads all the dependecies and may take a couple of minutes

$ make build   # this compile your app
$ make install # this installs the successfully compiled app to a connected badge.

# you really only need '$make install' because it depends on `install`. 

It will take a couple of minutes to download all the components. Once completed, a simple app showing “Hello, World!” will run on your badge.

Difference to “normal” IDF

If you have previously used the IDF, you may have noticed that we don’t use flash to install the app on the Badge. (And if you haven’t, you can safely skip this section. :)

The flash command assumes that the binary to flash is the main application for the device. This is not the case for the Badge, though. The main application is the launcher app, i.e. the app with the menu that starts by default. The make install target of the Makefile copies our newly created app into the appfs instead of overwrting the launch. Once copied to the appfs, the launcher can find it and the app should appear in the apps menu.

Obviously you can use flash but you’ll delete the launcher app and would need to reinstall it later.

Customizing the template app

Finally! Now that we have all the bureaucracy taken care of, we’ll start off by modifying the message printed to the screen. Have a look at this line of main.c, you can see the text shown on screen:

        // This text is shown on screen.
        char             *text = "Hello, World!";

This part is responsible for drawing the text to the screen. Go ahead and try to edit the text, here shown as “Fancy App!”:

(The text “Fancy App!” on a blueish green background.)

Reading the buttons

The buttons on the Badge are not directly connected to the ESP32, instead they are read by the rp2040 coprocessor via I2C. Have a look in the esp32-component-mch2022-rp2040 component in case you are interested in the details.

The button handler starting on this line of main.c currently causes the app to exit and return to the launcher whenever the HOME button is pressed.:

        // Await any button press and do another cycle.
        // Structure used to receive data.
        rp2040_input_message_t message;
        // Await forever (because of portMAX_DELAY), a button press.
        xQueueReceive(buttonQueue, &message, portMAX_DELAY);
        // Is the home button currently pressed?
        if (message.input == RP2040_INPUT_BUTTON_HOME && message.state) {
            // If home is pressed, exit to launcher.
        // Is the home button currently pressed?
        if (message.input == RP2040_INPUT_BUTTON_HOME && message.state) {
            // If home is pressed, exit to launcher.

Let’s change this behaviour so the screen is briefly pink after pressing the A button. Graphics for the badge are handled by a library called Pax, if you want to dig deeper have a look at the docs here

Pax uses the same RGB (well, ARGB, to be precise) hex triplets as HTML. 0xeb34cf is beautiful MCH pink.

        // Button handling.
        if (message.input == RP2040_INPUT_BUTTON_ACCEPT && message.state) {
                // Make a pink background.
                pax_background(&buf, 0xeb34cf);
                // Update the screen.
                // Wait for half a second.
                // After this, it loops again with a new random background color.
        } else if (message.input == RP2040_INPUT_BUTTON_HOME && message.state) {
            // If home is pressed, exit to launcher.

(A pink screen when the A button is pressed.)

Using WiFi

The template app you’ve been playing with has a simple WiFi connection API.

First, empty the while loop so it looks like this:

    while (1) {
        // Await any button press and do another cycle.
        // Structure used to receive data.
        rp2040_input_message_t message;
        // Await forever (because of portMAX_DELAY), a button press.
        xQueueReceive(buttonQueue, &message, portMAX_DELAY);
        // Is the home button currently pressed?
        if (message.input == RP2040_INPUT_BUTTON_HOME && message.state) {
            // If home is pressed, exit to launcher.

Instead of writing “Hello World” to the screen, we will modify the code to change the background color to indicate our Wifi connection status. Call wifi_connect_to_stored() to connect to WiFi and set the background color depending on whether the function returned successfully.

    // Init (but not connect to) WiFi.
    // Now, connect to WiFi using the stored settings.
    bool success = wifi_connect_to_stored();
    if (success) {
        // Green color if connected successfully.
        pax_background(&buf, 0xff00ff00);
    } else {
        // Red color if not connected.
        pax_background(&buf, 0xffff0000);

(A red screen and a green screen side by side.) (A red screen and a green screen side by side.)

What you want to do with WiFi varies a lot, so we can’t explain that here. But if you have other libraries that need WiFi (for example an MQTT client), you start them after this code.

Sharing is caring!

Now you’re ready to publish your app in the Hatchery. Follow these instructions to publish your app.

For further information:

4.1.2 - A More Advanced Example

If you have reached this page, you have probably already had a look at the template app and played through the getting started tutorial. If not, it might be a good idea to do it now - there’s a lot of information on getting the prerequisites installed.

You will need a computer with libusb, pyusb, git, cmake, make, python3, a terminal, a web browser and a text editor. This should be easily doable on Linux machines and Macs - if you’re on Windows, it’s probably easiest to work in a Linux wrapper but YMMV. Additionally, a github account is helpful but not strictly needed. Check here for details.

This journey assumes that you have some basic familiarity with shell, C and git (or a search engine of your choice). This is not a line-by-line tutorial, it just gives you the rough outline of writing an app and discusses some approaches and techniques along the way. If you want to cheat and download the finished project, go here


Start by cloning the template app - go there, click on “Use this template” and follow the instructions to make your own copy (or you can clone the repo and add a new remote manually). git clone the repo, cd to it and run make prepare. This should set up the ESP-IDF and all badge-specific components.

What should we do?

If you’re not sure what you want to hack, the ESP-IDF examples are an amazing starting point. They are already on your machine: ls esp-idf/examples. Hours of happy browsing. Besides covering many features of the ESP32, they are exceptionally well written and documented (usually).

We’ll use one of these app to build our app - something that can’t be done in the BadgePython world: Let’s turn the Badge into a bluetooth Boom Box. Speaker sound quality will most likely be worse than any smartphone on this planet, but with the headphone output, this thing might even be usable for something.

There’s a working example at esp-idf/examples/bluetooth/bluedroid/classic_bt/a2dp_sink. The code example already shows how to hook the audio stream to an I2S (Inter-IC Sound) DAC. And conveniently, the Badge’s audio outputs are connected to an I2S DAC! Almost like we’re done already before we even started.

Shameless Copying

To get started, copy the following files from the IDF project’s main directory: bt_app_av.h, bt_app_av.c, bt_app_core.h, bt_app_core.c into your own main folder (they are Public Domain, after all!). And while you’re at it, copy most of the contents of the main.c file over to the end of your main.c file and the includes to the top.

Actually Hacking Some Code …

Start by integrating the bluetooth initialization routine into your app. Rename the bluetooth example’s app_main to bt_init and call it within our app_mainfunction in place of the call to wifi_init ( we won’t be using WIFI in this example). bt_init must be declarated above app_main code. Either move the whole function up, or add a declaration.

Unfortunately, both app_main and bt_init call nvs_flash_init. And nvs_flash_init may only be called once. Get rid of the second call.

The example projects defines a number of constants using menuconfig. These are defined in Kconfig.projbuild, but we don’t need them. For example, this mechanism in the original IDF example allows you to redefine the I2S pins to use, but these are hardwired on the Badge, so configuring them adds unnecessary complexity. grep through main.c looking for CONFIG_EXAMPLE and replace them:

  • CONFIG_EXAMPLE_A2DP_SINK_OUTPUT_INTERNAL_DAC : should be false, this option would route the audio to the ESP’s internal DAC, but the Badge has a dedicated audio DAC chip

We need to find the new values for the I2S pins CONFIG_EXAMPLE_I2S_BCK_PIN, CONFIG_EXAMPLE_I2S_LRCK_PIN and CONFIG_EXAMPLE_I2S_DATA_PIN in i2s_pin_config_t. Obviously, you can find the pins in the hardware schematics, but there’s an easier way: Have a look at components/mch2022-bsp/include/mch2022_badge.h. The Badge’s board support package has defines for all pins. (Note: At time of writing, this header had LRCLK and BCLK swapped, but hopefully this will be sorted out soon).

The components directory is generally a good place to look if you’re looking for Badge drivers. All items in this folder are independent components. You can imagine them as libraries. They are automatically added to the project by the ESP-IDF build system.

I2S has some sloppy signal naming rules, which may be confusing. LR is LRCLK (a word clock), CLK is BCK (a bit clock) and DATA is DATA. In addition, our DAC wants a MCLK (usually faster than the bit clock), so we add an entry: .mck_io_num = GPIO_I2S_MCLK. In the end, it should look something like this:

    i2s_pin_config_t pin_config = {
      .mck_io_num = GPIO_I2S_MCLK,
      .bck_io_num = 4, // should be GPIO_I2S_CLK
      .ws_io_num = 12, // should be GPIO_I2S_LR
      .data_out_num = GPIO_I2S_DATA,
      .data_in_num = -1 // not used
    i2s_set_pin(0, &pin_config);

While you’re at it, you can tweak the I2S parameters to our needs (located directly above the pin_config code). I2S has half a dozen different dialects and each I2C peripheral speaks a different one. Getting the parameters right is not hard but tedious, requiring comparison of datasheets. Additionally, because the I2S peripheral will stream audio data via DMA, we can adjust buffer sizes. Here’s some settings that seem to work well:

    i2s_config_t i2s_config = {
      .mode = I2S_MODE_MASTER | I2S_MODE_TX, // TX only
      .sample_rate = 44100,
      .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
      .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT, // stereo
      .communication_format = I2S_COMM_FORMAT_STAND_I2S,
      .dma_buf_count = 6,
      .dma_buf_len = 128,
      .intr_alloc_flags = 0, // default interrupt priority
      .bits_per_chan = I2S_BITS_PER_SAMPLE_16BIT,
      .tx_desc_auto_clear = true // auto clear tx descriptor on underflow
    i2s_driver_install(0, &i2s_config, 0, NULL);

Almost Ready to Try

We’re close to getting something working. Just four things before we try our first build:

  • Change our app name: The projects Makefile contains an install target. It’s purpose is to push the project’s binary to the Badge during development. The name in quotes is the name shown on the Badge’s app chooser. Change it something unique.
  • Change the Speaker’s name: There’s a #define that we copied over from the bluetooth example: LOCAL_DEVICE_NAME. This is the name broadcast via bluetooth. Change it to something unique.
  • menuconfig: menuconfig allows you to enable and configure the components in your project. First, enable bluetooth. Start the tool with make menuconfig, go to Component config > Bluetooth and enable it. Go to Bluedroid Options and enable Classic Bluetooth and A2DP(Advanced Audio Distribution Profile = what bluetooth speakers do). Later on, menuconfig is a good place to disable unneeded software components. For now, we don’t care.
  • Add files to compile: Remember that we added additional ‘*.c’ files, bt_app_av.c and bt_app_core.c? The project’s build process works roughly as follows: make build triggers build which in turn uses cmake. For now you don’t need to understand this in detail,you just have to tell the build system about the new files. We need to edit main/CMakeLists.txt. When you’re done, the SRCS section should look something like this:

Now it’s time to make. Type make prepare, this downloads all the prerequisite tools and code. This process might take a while. It will fell like an eternity. Meanwhile, whistle the Jeopary theme song. Drink some water. Wash your hands. Give a polite, honest compliment to a stranger.

The make process should have finished by now. Now type make build. If this fails, you probably didn’t follow the steps properly (most likely the compliment part). No worries, subsequent builds will be faster.

Now, run make install. If there’s an error concerning missing USB, repeat the libusb and pyusb install steps. If you get a UnicodeEncodeError in printProgressBar, you’re using a Mac and you can solve this problem by editing tools/ Replace the fill character with another character, e.g. *. Or fix it and create your first PR to the tools repo!

If everything went as expected, you should see a WebUSB screen on the Badge and a progress bar in the terminal. Once upload and verification completes, the Badge should reboot and show the “Hello world” screen of the template app. … Boring!

Take your phone or other bluetooth device, scan for new devices. Select BadgeBoomBox or whatever you chose for your speaker’s name and pair them. Make sure the speaker switch on your Badge is turned on. Play some music. Hear it? That amazing sound of no bass? Unbelievable.

Understand What’s Going On

Good work! Let’s take a short break and look at what the app is doing (hey, we didn’t write much of it yet). ESP-IDF has a logging facility that is used in the example code (look for ESP_LOGI, ESP_LOGE, ESP_LOGD etc.). We can monitor the logs with make monitor (if it does not work, you might want to set the PORT environment variable to the ESP’s /dev/tty* ). If you succeed, you will see bluetooth connection and disconnection events and all sorts of interesting things happening. For example:

  • There are “volume change simulation” events. Too bad we didn’t look into the example before - the example code simulates volume controls and a user randomly turning the volume up and down to showcase the AVRC (Audio/Video Remote Control) features. This has to go. But just the “random volume change” part - we may want to hook the volume control to our buttons. The simulation is executed in a separate task, look for s_vcs_task_hdl in bt_app_av.c and surgically remove it from the source code along with volume_change_simulation.

  • If you connected specific devices, e.g. an Android phone, you might be surprised to see that the phone will not only send connect/disconnect and play/pause events, but sometimes also track titles as well as album and artist names. Wouldn’t it be great to see this on the screen?

AVRC is not consistently used by all devices. Some features are used, some not. Anyway, let’s have some fun with it.

Another nice thing to have would be a dB-Meter. Our next task is to sift through the code to see where the audio stream passes by to analyze it.

Side note: Tasks, Events, FreeRTOS messaging and our threading approach

ESP-IDF makes heavy use of FreeRTOS. Two essential building blocks of FreeRTOS are Tasks and Queues. Tasks can be seen as threads: Independent, preemptively scheduled sequences of operation. Each application has a main thread (the one that executes app_main), a timer thread and possibly other threads (e.g. for bluetooth, Networking and other things). Queues are often used to pass events and other information from one task to another. They are basically thread-safe FIFO buffers. One task (or an interrupt) posts elements into the queue and another task can wait for elements to arrive in that queue.

The template app already uses one queue: The RP2040 firmware will post button presses into this queue. The application’s main loop waits for button press events to arrive and reacts to it by setting a new random color and redrawing the screen.

The bluetooth stack uses its own tasks. Our task, the main task, controls the screen and user interaction (and it’s a good idea to restrict this to a single task). So if we want to receive bluetooth information in the main task, it’s a good idea to use a queue. bluetooth event -> queue -> main task reacts.

But our main task is already blocked waiting for the button press queue! How can we receive our Bluethooth events? Could we use the button queue for our bluetooth events? Yes you could! But it’s not polite to push things into other’s queues without prior consent. So we don’t.

There’s another option: Queue sets are used to combine queues and (other things) and wait on several events simultaneously.

So we’ll create a new audioQueue to send us messages whenever there’s a relevant bluetooth and/or audio event. We also use this queue to send audio level updates regularly.

Queue entries can have data attached to them. This is often a struct with an event type and additional data, typically implemented as a union so that different events can have different data associated with them. It’s good practice to keep these entries short because queues will have to allocate several instances prior to usage (Real Time OSes prefer allocating a fixed amount of memory at start instead of dynamically allocating memory during runtime).

To keep the queued data short, we will not include the full audio stack state in the queue entries. Instead we’ll generate an event to notify that the state changed, but not what actually changed. For this, we use another mechanism to get data safely from one task to another: Semaphores used as mutexes / locks. The bluetooth stack will collect its own state in a struct. The main task can request a copy of that state struct. All accesses to members of that struct will be embedded in a lock, making sure that only one task has access to this struct at any instance in time.

Queues are good for pushing information from one task to another, mutexes are good for pulling. Admittedly, we could have used just queues in this case, but this example is supposed to be at least slightly educational…

In addition to the “something changed in the bluetooth audio state” event, we will have a dB-Meter-update event that should be sent in roughly 20-50Hz intervals so that we can have a smooth noise meter animation.

Who should manage the queue? The queue could be located either in the bt_app_*** part or in our main.c. Both are good options. We will add them to main.c, reasoning that the bt_app_*** is a generic service and should not make any assumptions about hosting application. As a consequence, the bt_app_*** part will just issue callbacks whenever something interesting happens. The code we’ll write in main.c takes care of queueing these events.

We will leave the well-paved path of documenting every changed part in the code here. The remaining document will show some examples. As said, the full code is in the repository.

Getting metadata

After some light reading, you’ll quickly get a better overview over the bluetooth app: naming suggest that bt_app_core.c seems to do the actual streaming while bt_app_av.c handles metadata and remote control. So the audio data is more likely to be found in bt_app_core.c. And metadata is most likely found in bt_app_av.c.

We need to decide: What data is useful for us? What could we want to display?

  • Connection state: Whether we’re disconnected, connected, connecting or disconnecting
  • Audio playback state: Whether we’re playing, stopped or suspended (which is, in effect, also stopped somehow)
  • The current volume: A value between 0..127
  • Our current sample rate (no idea if someone is interested but anyway, let’s collect it)
  • Current title, artist and album (if available)

So a simple struct to hold that state should look something like this:

/** the full exposed audio state in a struct */
typedef struct BTAudioState_ {
  esp_a2d_connection_state_t connectionState;  // 0=disconnected, 1=connecting, 2=connected, 3=disconnecting
  esp_a2d_audio_state_t playState;  //0=suspended, 1=stopped, 2=playing
  uint8_t volume; //0..127
  int sampleRate;
  char title[AUDIOSTATE_STRLEN];
  char artist[AUDIOSTATE_STRLEN];
  char album[AUDIOSTATE_STRLEN];
} BTAudioState;

So what do we do now? Look into the logs (remember make monitor) for the data we’re interested in. Find the code that generated the log messsage. Insert code to update our state. Be sure to lock each access to the struct. After a change, push an entry to the event queue. It’s a good idea to clear the state when we get disconnected.

For example, we insert four lines to handle ESP_A2D_AUDIO_STATE_EVT, an event sent whenever the actual stream is started, stopped or suspended:

        a2d = (esp_a2d_cb_param_t *)(p_param);
        ESP_LOGI(BT_AV_TAG, "A2DP audio state: %s", s_a2d_audio_state_str[a2d->audio_stat.state]);
        s_audio_state = a2d->audio_stat.state;
        if (ESP_A2D_AUDIO_STATE_STARTED == a2d->audio_stat.state) {
            s_pkt_cnt = 0;
        audioState.playState = a2d->audio_stat.state;

There are other parts where the state is updated, but they all follow the same principle, so it would be boring to list them all here. Try yourself! Or have a look at the repo. lockAudioState()acquires the lock, unlockAudioState() releases it and notifyAudioStateChang() pushes an event to our queue.

Tapping the audio stream

bt_app_core.c has two tasks: The bt_app_task that responds to bluetooth stuff and the bt_i2s_task that seems to stream the audio data to the I2S peripheral. Bingo! That’s ideal!

Have a look at bt_i2s_task_handler: This function mainly consists of an endless loop waiting on a ring buffer to deliver sample data and pushes that data into the i2s peripheral. We can hack that! First, we want to implement volume control by scaling each sample. Second, we want to calculate the audio volume. Have a look:

static void bt_i2s_task_handler(void *arg) {
    uint8_t *data = NULL;
    size_t item_size = 0;
    size_t bytes_written = 0;
    static float leftSquares = 0;
    static float rightSquares = 0;
    static int sampleCount = 0;

    for (;;) {
        /* receive data from ringbuffer and write it to I2S DMA transmit buffer */
        data = (uint8_t *)xRingbufferReceive(s_ringbuf_i2s, &item_size, (portTickType)portMAX_DELAY);
        if (item_size != 0){
            int16_t *buf = (int16_t*)data;
            int numSamples = item_size / 2;
            uint8_t vol = getVolume();
            float volScale = volumeScale[vol] / 65536.0f;
            // Sample processing can go here. Right now, only volume scaling and RMS analysis
            for (int i=0; i<numSamples; i += 2) {
                float l = (float)buf[i];
                l *= volScale;
                leftSquares += l*l;
                buf[i] = l;
                float r = (float)buf[i+1];
                r *= volScale;
                rightSquares += r*r;
                buf[i+1] = r;
            sampleCount += numSamples;
            i2s_write(0, data, item_size, &bytes_written, portMAX_DELAY);
            vRingbufferReturnItem(s_ringbuf_i2s, (void *)data);
            if (sampleCount >= 1500) {
              notifyAudioRMS(sqrtf(leftSquares / sampleCount), sqrtf(rightSquares / sampleCount));
              leftSquares = 0;
              rightSquares = 0;
              sampleCount = 0;

This code is by no means elegant nor efficient. First, we cast the data buffer to an int16 array (we know that we have 16 bit samples and I2S has them typically interleaved, L/R/L/R/…). For each buffer, we request the current audio volume, get a scaling factor via a lookup table (perceived volume is logarithmic). Then we go through all left and right samples, convert each to float and multiply it with our volume factor. Then we convert the sample back to int and replace the sample in the buffer with our scaled value.

We also square each sample and sum the squares for the left and right channel. After 1500 samples (roughly every 30ms for 44KHz), we divide the the sum of squares by the number of samples, resulting in the mean square, and then take the square root, resulting in the Root of the Mean Square (RMS). That’s a good basis for a volume display. notifyAudioRMS() will push an audio RMS update to the event queue. After reporting, we reset the accumulators for the next interval.

Converting everything to float and back is terribly unneccessary and terribly slow. But the ESP is fast enough and this is a good starting point for further DSP (anyone?).

Bring it together

Now that we have extended the bluetooth audio code to give us callbacks whenever something happens, it’s time to bring it all to the main loop. Let’s see what we should do in the main loop:

  • Audio state changed: Pull audio state, redraw screen
  • Audio RMS levels changed: Remember levels, redraw just the level meter
  • Home button pressed: Exit to launcher
  • Joystick up or down: Increase or decrease volume, redraw all

First, write typedefs and structs that can hold audio events (state changes or RMS updates):

typedef enum BTAudioEventType_ {
  Event_StateChanged = 1, ///< audio state has changed, may be queried using getAudioState
  Event_RMSUpdate        ///< audio RMS update
} BTAudioEventType;

typedef struct BTAudioEvent_ {
  BTAudioEventType type;
  union {
    struct {
      float left;
      float right;
    } rms;
  } data;
} BTAudioEvent;

Next generate a queue to hold these events:

xQueueHandle audioQueue;
audioQueue = xQueueCreate( 10, sizeof(BTAudioEvent) );

Now we need callback functions to call from the bluetooth part (running in the the bluetooth task!). Their purpose is to push a BTAudioEvent into the audioQueue:

/** callback from bt_app_av: state has changed */
void audioStateChange() {
  BTAudioEvent evt = {
    .type = Event_StateChanged
  xQueueSend(audioQueue, &evt, 0);  //evt is copied to queue

/** callback from bt_app_core: new volume measurement */
void audioRMSUpdate(float left, float right) {
  BTAudioEvent evt;
  evt.type = Event_RMSUpdate; = left; = right;
  xQueueSend(audioQueue, &evt, 0); //evt is copied to queue

Next, register the callbacks (not shown: They will just be stored in global variables and called when necessary)


At this point, updates from the bluetooth stack will end up in our audioQueue. Time to combine the queues:

  QueueSetHandle_t queueSet = xQueueCreateSet(20);
  xQueueAddToSet(buttonQueue, queueSet);
  xQueueAddToSet(audioQueue, queueSet);

Finally, we can write our main event loop:

  while (1) { //handle events from both button and audio queue
    QueueSetMemberHandle_t queue = xQueueSelectFromSet(queueSet, portMAX_DELAY);
    if (queue == buttonQueue) {
      rp2040_input_message_t message;
      xQueueReceive(buttonQueue, &message, 0);
      if (message.state) {
        switch(message.input) {
          case RP2040_INPUT_BUTTON_HOME:
          case RP2040_INPUT_JOYSTICK_UP:
            volume_set_by_local_host(audioState.volume < 122 ? (audioState.volume+5) : 127);
          case RP2040_INPUT_JOYSTICK_DOWN:
            volume_set_by_local_host(audioState.volume > 5 ? (audioState.volume-5) : 0);

    } else if (queue == audioQueue) { //audio event
      BTAudioEvent evt;
      xQueueReceive(audioQueue, &evt, 0);
      if (evt.type == Event_StateChanged) { //state changed: update main UI
      } else if (evt.type == Event_RMSUpdate) {  //RMS: Update bars
        float leftDB = 20 * log10(;
        float rightDB = 20 * log10(;
        leftDBMeter = (leftDB - DBMETER_MIN) / (DBMETER_MAX - DBMETER_MIN);
        rightDBMeter = (rightDB - DBMETER_MIN) / (DBMETER_MAX - DBMETER_MIN);

The xQueueSelectFromSet will wait until am event arrives in one of the queues and return which queue was active. The rest is dispatch: If the origin was the button queue, react to button or joystick input. If it was an audio event, redraw the level meter or the whole screen. The RMS update will convert the RMS to dB by calculating the logarithm (as said above, perceived volume is logarithmic). Then, the values will be scaled to fill the screen. The values DBMETER_MIN and DBMETER_MAX are arbitrarily chosen so that the level meter shows something useful.

Show it!

We’ve put some effort into collecting and merging data to display. Now it’s time to visualize the data. The Badge comes with a convenient graphics package that allows us to draw shapes and write text. It draws to a bitmap and then transfers the bitmap to the screen. Currently, the transfer to screen is not very fast as it uses the MCU to control the transfer (anyone interested in implementing DMA transfers? Pull Request, plz!). Smooth fullscreen animations will be difficult. However, it’s possible to just transfer parts of the buffer. The only smooth animation we need is the level meter.

For simplicity, let’s draw that as a horizontal bar graph (expanding to the left and right from center for the left and right channel) at the bottom of the screen and put it in a separate drawing function, drawDBMeter(). The remaining screen is drawn in drawAll(), which will, in turn, call drawDBMeter(). This way we can either update the DB graph quickly or the whole screen slowly. Both functions will transfer their parts to the screen.

void drawDBMeter() {
  if ((audioState.connectionState != ESP_A2D_CONNECTION_STATE_CONNECTED) || (audioState.playState != ESP_A2D_AUDIO_STATE_STARTED)) {
    leftDBMeter = 0;
    rightDBMeter = 0;
  int halfWidth = (ILI9341_WIDTH / 2);
  float l = (leftDBMeter < 0) ? 0 : (leftDBMeter > 1) ? 1 : leftDBMeter;
  float r = (rightDBMeter < 0) ? 0 : (rightDBMeter > 1) ? 1 : rightDBMeter;
  int leftPix = halfWidth * l;
  int rightPix = halfWidth * r;
  int p1 = halfWidth - leftPix;
  int p2 = halfWidth + rightPix;
  pax_col_t bgCol = pax_col_rgb(0,0,0);
  pax_col_t fgCol = pax_col_rgb(255,255,255);
  pax_simple_rect(&screenBuf, bgCol, 0,  y, p1, DBMETER_HEIGHT);
  pax_simple_rect(&screenBuf, fgCol, p1, y, p2-p1, DBMETER_HEIGHT);
  pax_simple_rect(&screenBuf, bgCol, p2, y, ILI9341_WIDTH-p2, DBMETER_HEIGHT);
  int off = 2 * ILI9341_WIDTH * (ILI9341_HEIGHT-DBMETER_HEIGHT);
  ili9341_write_partial_direct(get_ili9341(), screenBuf.buf+off, 0, ILI9341_HEIGHT-DBMETER_HEIGHT, ILI9341_WIDTH, DBMETER_HEIGHT);

The code relies on the audioState struct and the leftDBMeter and rightDBMeter variables (all are local to the main task, so we don’t need to worry about threading here). DBMETER_HEIGHT is a global variable determining the height of the bar in pixels and ILI9341_WIDTH and ILI9341_HEIGHT are variables defined in the display driver component included with the template app. Drawing is pretty straightforward:

  • If we’re currently not playing music, the meter should be at zero
  • Levels are clamped and then scaled to screen size
  • The bar graph always consists of a white rectangle in the middle and two black rectangles at the sides. It would be slightly easier to fill the whole area black and then a white rectangle over it, but that would touch some pixels twice. The three-rectangles-approach only sets each pixel once.
  • In the end, the ili9341_write_partial_direct() call transfers the screen portion of the bar graph to the screen.

The drawAll() function is longer but even easier:

void drawAll() {
  static const char disconnected[] = "Disconnected";
  static const char connecting[] = "Connecting...";
  static const char disconnecting[] = "Disconnecting...";
  static const char stopped[] = "Stopped";
  static const char playing[] = "Playing";
  pax_col_t bgCol = pax_col_rgb(0,0,0);
  pax_background(&screenBuf, bgCol);

  pax_col_t fontColor = pax_col_rgb(255,255,255);
  const char *status = "?";
  switch (audioState.connectionState) {
      status = connecting;
      status = disconnecting;
      status = disconnected;
      status = (audioState.playState == ESP_A2D_AUDIO_STATE_STARTED) ? playing : stopped;

  char volStr[30];
  snprintf(volStr, 30, "Volume: %i%%",audioState.volume * 100 / 127);

  pax_draw_text(&screenBuf, fontColor, pax_font_saira_condensed, pax_font_saira_condensed->default_size, 10, 10, status);
  pax_draw_text(&screenBuf, fontColor, pax_font_saira_regular, pax_font_saira_regular->default_size, 10, 90, audioState.title);
  pax_draw_text(&screenBuf, fontColor, pax_font_saira_regular, pax_font_saira_regular->default_size, 10, 115, audioState.artist);
  pax_draw_text(&screenBuf, fontColor, pax_font_saira_regular, pax_font_saira_regular->default_size, 10, 140, audioState.album);
  pax_draw_text(&screenBuf, fontColor, pax_font_saira_regular, pax_font_saira_regular->default_size, 10, 165, volStr);

  ili9341_write_partial_direct(get_ili9341(), screenBuf.buf, 0, 0, ILI9341_WIDTH, ILI9341_HEIGHT-DBMETER_HEIGHT);

The function just clears the screen and then writes some text to it. Most of the code just determines the message to draw. ili9341_write_partial_direct() transfers everything except for the volume meter and calls drawDBMeter() to update that part.

This should be it. Make and install again (and, if needed, debug, rinse, repeat). There should be awesome sound and an awesome user interface.


The hatchery also allows publishing native apps. Go to The Hatchery, register, login. There should be an option to publish native ESP32 apps. This tutorial is already way to long, though. Follow these instructions if you want to publish your app in The Hatchery

4.1.3 - ESP-IDF fancy name tag

There are endless games and apps to explore on the badge, but when going about your business on the camp, most likely its main function will be a name tag. So what better than writing a custom name tag to show off your style, identity, hacker skills, memes, or whatever you want.

After having completed the getting started you should have a template app that can draw a colored background and some text. Change the text to your name, and you have yourself a name tag… right? Let’s explore some ways in which you can spice up your name tag.

Other drawing functions

The pax-graphics documentation has quite a nice list of all the fonts and drawing primitives it contains.

Drawing lines and circles may sound a bit boring, but if you duck “line patterns” or “geometric pattern” or similar queries you can find quite some nice patterns to draw with those basic shapes.

In addition I’d like to draw your attention to the shaders documentation which has a nice example to draw rainbows on shapes, which you could easily adapt to do all sorts of nice gradients.

Drawing images

Geomeric patterns are nice, but if you want to show off your art, the logo of your favourite retrocomputer, a character from your favourite franchise, or your favourite meme, you’ll want to load images onto the screen.

The pax-graphics side of drawing images is well documented. But before you get to that point, there are a few things you need to do.

Of course first you need to find or make an image. This part is up to you. Keep in mind that the badge screen is 320x240 pixels, and that pax-graphics only loads png.

Next you’ll need to get the image onto the badge. Since internal flash space is extremely limited, it’s highly recommended to use a micro SD card. Be careful when inserting it! To push the png image to the SD card:

python3 tools/ myimg.png /sdcard/myimg.png

To use the SD card, you need to include the component, and mount it. Then you can open the file.

#include "sdcard.h"

// image buffer
static pax_buf_t myimage;

// mount sd card
esp_err_t res  = mount_sd(GPIO_SD_CMD, GPIO_SD_CLK, GPIO_SD_D0, GPIO_SD_PWR, "/sd", false, 5);
if(res != ESP_OK) ESP_LOGE(TAG, "could not mount SD card");

// open file
FILE* fd = fopen("/sd/myimg.png", "rb");
if(fd == NULL) ESP_LOGE(TAG, "could not open file");

// store as a buffer for later use, best for animations
if(!pax_decode_png_fd(&myimage, fd, PAX_BUF_16_565RGB, 0)) ESP_LOGE(TAG, "could not parse png");
pax_draw_image(&buf, &myimage, x, y);

// or draw directly, simplest for static drawings
if(!pax_insert_png_fd(&buf, fd, x, y, 0)) ESP_LOGE(TAG, "could not parse png");

If you do not have a micro SD card, and you only want to load a small image, you can also mount the internal filesystem instead.

Making animations

An animation is just some static drawings in a row. Once again, it’s what you do with it.

The template app already has an infinite loop that waits forever until a button is pressed. Do not remove that part! The ESP32 is running an RTOS that needs to do some book keeping in the background. Without some delay somewhere you’ll get watchdog timer errors. However, you can change the line to the following, to only wait a few milliseconds instead of forever. Tweak this number to get the frame rate you want, or to make a nice slideshow.

xQueueReceive(butonQueue, &message, pdMS_TO_TICKS(1));

If you can’t get the framerate you want, and are doing a lot of rendering in pax-graphics, you can offload that to the second core for a free speed boost.


If that still isn’t fast enough, you should hop over to the FPGA section, which has a faster parallel bus to the display.

As for what kind of animations to make, a great source of inspiration is demoscene videos. Here is a page that has some implementations of a few of the classic effects, but there are plenty of other cool effects to be found all over the internet. Who’s going to implement Nyan Cat, Bad Apple, old Windows screensavers, and more?

RGB galore

The badge includes a kite of RGB LEDs, which you can do cool blinkenlights with. The API is pretty simple: First you need to enable the power gate to the LEDs, then you init it with the correct output pin, and then you send an array of PWM values.

#include "ws2812.h"

// enable power to the LEDs
gpio_set_direction(GPIO_SD_PWR, GPIO_MODE_OUTPUT);
gpio_set_level(GPIO_SD_PWR, 1);
// initialise them
// send data
uint8_t led_red[15] = {0, 0xFF, 0, 0, 0xFF, 0, 0, 0xFF, 0, 0, 0xFF, 0, 0, 0xFF, 0};
ws2812_send_data(led_red, sizeof(led_red));

As an example, here is the kite animation that plays when you start the badge.

Making sound

TODO: There isn’t a nice API for this yet. You can steal some code from the launcher maybe.

Using sensors

TODO: Make some nice example with the BNO055 component

4.2 - FPGA Development


git clone
git clone --recursive
python3 mch2022-tools/ mch2022-firmware-ice40/projects/Hello-World/hello_world.bin

If the TL;DR wasn’t wordy enough for you, try “FPGA Getting Started for Badgers with Tiny Brains” or read on!

If you look for a beginner friendly, graphical FPGA development suite:


The badge contains an ice40 FPGA that is connected to a PMOD connector, a serial QSPI RAM, and a RGB LED. It can also control the display over a parallel bus, and has an USB UART link via the RP2040 and an SPI link to the ESP32 which notifies the FPGA on the state of the buttons and offers read access to large data files.

You can start with having a look at the top-level diagram of the badge hardware of the complete badge, then proceed to the schematic and pin constraints file.


As with all the other methods to program the badge, step one is to download mch2022-tools. There are two main tools to use here, python3 bitstream.bin which will upload a bitstream directly into the FPGA, and python3 bitsream.bin /sdcard/apps/ice40/myapp/bitstream.bin which will make the bitstream available in the launcher.

The easiest way to install the tools needed to synthesise bitstreams for the FPGA is oss-cad-suite.

You can also build Yosys, Icestorm, and NextPNR from source.

Do not try to install packaged Yosys/NextPNR/Icestorm tools that might come with your distro – the toolchain is advancing very, very quick, and if your distro packaged it three months ago, it is already heavily outdated. The ones in Debian Stable – Ouch!

The main repository with templates and examples is mch2022-firmware-ice40. Running make in any of the folders in the projects directory should produce a bitstream in separate build-tmp subfolder. Also take note of the cores folder, which contains many useful cores for basic functionality, such as providing the FPGA as a peripheral to the ESP via SPI and others.

The FPGA can kind of be used in two seperate modes: standalone and peripheral mode.


When launching a bitstream from the launcher, the ESP32 hands over control of the display to the FPGA, and exposes an API for reading buttons and files.

A simple example to read the buttons is found in buttons.v

A more elaborate example of a full-fledged RISC-V SoC with a wishbone bus and video output can be found in riscv_doom. While the example is runing Doom, but it’s actually a full featured RISC-V processor so it’s possible to change the RISC-V code running on it, add or modify peripherals on the wishbone bus, etc.

The file read interface uses data files either temporarily uploaded along with the bitstream you are currently working on as riscv-playground.bin 0xdabbad00:fw/tinyblinky/tinyblinky.bin or put into the filesystem as fpga_dabbad00.dat in the same folder as the bitstream itself. You can use multiple data files with different 32-bit hexadecimal file identifiers.


If you want to think of the badge solely as FPGA dev board, you can ignore most of its other functionality, just keep in mind these handy hints:

  • The two UART lines are routed to /dev/ttyACM1, your terminal program selects the baud rate.

  • The FPGA should control the RGB LED using the SB_RGBA_DRV hard macro with constant current capabilities instead of a simple Verilog outputs, as that would overdrive at least the red LED.

  • The FPGA shall wait for then lcd_mode pin that switches between SPI/parallel mode of the LCD to go high before starting to talk to the LCD, as it is driven by the ESP32.

  • Check twice before connecting external voltages to the PMOD :-)

Example projects for standalone mode

This is a list of Verilog examples available in

There is also a collection of examples written in Silice:


Three different blinkies are available for a bright first experience:


A small example on how to get the state of the buttons. This is not trivial as the buttons are not connected to the FPGA.


A light emitting diode can shine, but it can also detect light. This contains an UART <-> Ledcomm bridge that allows one to transfer data between two badges just using a pair of LEDs. Still confused? Read the original paper

Forth Pmod Lab

Soldered something special for the Pmod connector? The Forth Pmod Lab helps you to quickly examine your hardware using the Forth language. Due to extensive documentation also suitable if you want to try Forth for the first time.


A free interpretation of the classic “snake” game with ASCII art and a Ledcomm based two-player mode. Enjoy!


A complete beginner friendly RISC-V ‘fantasy microcontroller’ that deserves its own documentation.


Does it run Doom? Of course!

Peripheral mode

Both the C++ and the Python API contain a convenience function to load a bitstream into the FPGA from your ESP32 program. This allows the FPGA to be used as a peripheral for the ESP32 processor, think AI coprocessor, bitcoin mining, HDMI output…

A great way to get started with this is to use the spi_skeleton example, which exposes a wishbone bus to the ESP32 over SPI.

This mode could be used to add an UART port on the PMOD by adding the following code, adjusting the top level ports and incrementing WN.

	// UART [2]
	// ----

	uart_wb #(
	) uart_I (
		.uart_tx  (uart_tx),
		.uart_rx  (uart_rx),
		.wb_addr  (wb_addr[1:0]),
		.wb_rdata (wb_rdata[2]),
		.wb_we    (wb_we),
		.wb_wdata (wb_wdata),
		.wb_cyc   (wb_cyc[2]),
		.wb_ack   (wb_ack[2]),
		.clk      (clk),
		.rst      (rst)

On the ESP32 you could then write the following Python script that loads a bitstream and writes to the newly added UART port.

import mch22
from fpga_wishbone import FPGAWB

# load bitstream from SD card onto the FPGA
with open("/sd/apps/ice40/myapp/bitstream.bin", "rb") as f:

# create a wishbone command buffer
c = FPGAWB()
# setup UART
# (30e6/9600)-2
c.queue_write(2, 4, 3123)
# queue writing a byte
c.queue_write(2, 0, 0xaa)
# queue reading a byte
c.queue_read(2, 0)
# execute the command queue

Example projects for peripheral mode


Badge hardware ok next to the FPGA? The selftest checks for that and reports back to the ESP32.


The SPI to RGB bridge gives the ESP32 control over the RGB LED, which is directly connected to the FPGA.

Guide for complete newbies to FPGAs

Let’s try for short:

For a bunch of TTL logic chip to do something useful, you need to wire them up - and the way you wire these determines the function of the completed circuit.

A “Field Programmambe Gate Array” contains a grid of “universal gates” called lookup-tables with -in our case- 4 binary inputs and 1 output, and every of these is accompanied by 1 flipflop bit. Nothing special so far. The special sauce of an FPGA is their connection - that there is a dense mesh of wires in different lengths that crisscross the entire chip, with switchbox points that allow to choose how to connect the individual logic elements to the mesh of wires. By selecting which switchboxes to activate, one builds an actual digital circuit on the FPGA.

For your curiosity, here is a DIY FPGA:

You should have an idea by now! You are going to build logic circuits. And you’ll probably fall into a rabbit hole :-)

Check out our “FPGA Getting Started for Badgers with Tiny Brains” guide for step by step information getting from 0 to a hardly working FPGA setup, in case you never heard of FPGAs before.

We would love to give you a more complete intro, but for time-is-not-infinite reasons, recommend you intros from others instead.

For the ones that prefer reading and want to know everything to design their own RISC-V CPU at the end of the course:

For the ones that prefer videos and a calm pace, Shawn Hymel has done a series in 12 parts that really starts at the beginning and explains the scenery you encounter:

4.2.1 - FPGA Getting Started explained by a Badger with a Very Small Brain

Ok let’s get real.

FPGA development is different from regular computer programming. It’s not necessarily more difficult, but the concepts involved are very different.

The number one difference is: in programming everything happens one things after another. With FPGAs, everything happens at once. This probably does not make sense yet, but it will.


What even is an FPGA?

FPGA stands for Field Programmable Gate Array. A “normal” chip like the ESP32 can also be considered a Gate Array. It’s an array of logic gates gates (NANDs ORs NOTs, etc.) that are wired together to form an ESP32 CPU. An FPGA also contains a bunch of logic gates. But they aren’t wired together. You write a (kinda) program to explain the way the gates are supposed to be wired together. This probably does not make sense without an example. So let’s get started.


The (kinda) programming language almost all the examples use will be Verilog. It looks like this:

	// this is what comments look like
	/* or like this */

	// verilog is structured into `modules`
	module AND (input  a,   // modules have `wires` coming into them
	            input  b,
	            output c);  // or going out. Direction matters.
		                // there is also `inout`

		    // everything else is _just_ like Javascript.
		    assign c = a & b; // semicolons are mandatory

	endmodule // unless they're no. It depends.

The code above builds a logical AND abstraction. It take a and b coming into the module, and’s them together and assigns the resulting value to c. When the code gets run through the toolchain (the analog of “compiling” in FPGA-lang is synthesis) the toolchain search in its database for unused structures within the target FPGA that can be used to create such an AND.

These structures are called look-up tables (LUTs), because they can be configured to take a bunch of inputs and look up what the output should be in a table. For our AND the configured LUT will look like this:


This is still really abstract

Install the tools

Ok, let’s get started for real. First clone out repo :

$ git clone --recursive
	Cloning into 'mch2022-firmware-ice40'...
	remote: Enumerating objects: 1333, done.
	remote: Counting objects: 100% (345/345), done.
	remote: Compressing objects: 100% (229/229), done.
	remote: Total 1333 (delta 193), reused 251 (delta 115), pack-reused 988
	Receiving objects: 100% (1333/1333), 1.97 MiB | 4.15 MiB/s, done.
	Resolving deltas: 100% (690/690), done.
..... 8< ....  snip snip snip boring .....

$ cd mch2022-firmware-ice40/
$ cat
..... 8< ....  snip snip snip boring .....

Get the latest package for your computers architecture:

..... 8< ....  snip snip snip boring .....

… and then download all the necessary tools from

$ mkdir toolchain && cd toolchain

oss-cad-suite-linux-arm64 47%[================>                     ] 185,29M  6,93B/s    eta 31h
..... 8< ....  snip snip snip boring .....

$ cd ..
$ source toolchain/$WHATEVER/environment

Awesome you’re ready. Let’s get started for real. All the examples are in the projects subdirectory in the mch2022-firmware-ice40 folder that you cloned from Git.

  • _common : stuff needed everywhere
  • Buttons : ~fairly simple example that wires together all the buttons to change the RGB LED colors
  • Fading-RGB : even simpler example that just fades the LEDs
  • Fading-White : …
  • Forth : a stack CPU that’s designed to run Forth
  • Hello-World : looks like a good starting place !
  • Ledcomm : … have a look around
  • riscv_doom : game. running on a cpu synthesized onto the FPGA
  • RISCV-Playground : … it’s 47 degrees C
  • selftest : … you need to do some looking around yourself.
  • Snake : better game
  • spi_skeleton : … it build character
  • spi-to-rgb : … and I’m lazy

So, if you looked around, all the examples are structured similarly:

  • they contain a Makefile we use this to turn the designs into bitstream. Those are basically a bunch of bits that are used to configure or Program the Array of Gates. And you are sitting in a Field.
  • Most already contains a *.bit file. This is the bitstream for the example. You could just load it to the badge.
  • There is an rtl directory containing *.v files. *.v is the extension for Verilog. RTL stands for “Register Transfer Logic (or Language” and describes the aspect of Verilog that looks more like Javascript but is able to be converted into logic gates.
  • The CPU projects also contain software to run on the CPU and possibly a toolchain to compile the software
  • misc other stuff

ENOUGH ALREADY you’re boring me to pieces …

Build the Project

Ok, we’ll start with ‘Hello World’. If you followed the instructions, you just need to type make and everything works:

$ make
cd /mch2022-firmware-ice40/projects/Hello-World/build-tmp && \
	yosys -s /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.ys \
		 -l /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.synth.rpt
/mch2022-firmware-ice40/toolchain/oss-cad-suite/bin/yosys: line 6: /mch2022-firmware-ice40/toolchain/oss-cad-suite/lib/ cannot execute binary file: Exec format error
/mch2022-firmware-ice40/toolchain/oss-cad-suite/bin/yosys: line 6: /mch2022-firmware-ice40/toolchain/oss-cad-suite/lib/ Success
make: *** [../../build/ /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.json] Error 126

Urgh. I screwed this up, but because one or two of you will screw this up as well, I thought I’d leave it in. If you look carefully at the error message, you’ll see something about aarch64. Which is ARM stuff. I’m using Badger-Basic on an x86, so I downloaded the wrong tools. Drat. (I actually managed to download the wrong tools twice :m)

… Several minutes later …

$ make
cd /mch2022-firmware-ice40/projects/Hello-World/build-tmp && \
	yosys -s /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.ys \
		 -l /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.synth.rpt

.... 8< ....  snip snip snip totally not boring but lots of it ..... 

Info: Program finished normally.
icepack -s /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.asc /mch2022-firmware-ice40/projects/Hello-World/build-tmp/hello-world.bin

Ok. Are we done yet?

Install on the Badge

Almost. Now we only need to push the newly generated bitstream onto the badge. And then we get to the exciting part: explaining how it all works! Use the webusb tools to push the bitstream:

 $ cd ../../tools/
 $ python ../projects/Hello-World/hello_world.bin 
Waiting for ESP32 to boot into FPGA download mode...
Sending bitstream : ...................................................

If this didn’t work, and there are error messages concerning USB, you need to install pyusb. Try something like:

$ pip install pyusb
... or
$ apt install python-usb


What you can’t tell from the picture is that the LED is actually blinking. In different colors. Super cool.

So … you said you’ll explain how this all works…

I also said I’m lazy and it’s 47 degrees Celcius. This section may be expanded upon or left abandoned with good intentions of finishing it up before MCH2022. *cough*

If it’s not done, either read the more about advanced examples or head over to the fpga repo, there is a lot of information there. Also, come by the workshops at the camp to chat.

Further Resources

No matter how far we get, this will not turn into a “Learning Verilog” Tutorial. Here is a list of resources we like to learn more about FPGA development:

4.3 - Developing Badge Apps with MicroPython

This is the starting point for BadgePython development. There’s an introduction / tutorial to get you started. We highly recommend to play through this tutorial as it will also tell you how to build Badge apps and some caveats during this process.

The tutorial will show you how to access the display and buttons. Here’s a guide on how to access the NeoPixel LEDs. This section will eventually (hopefully) fill with documentation on other peripherals. This is still work in progess. Please feel free to contribute…

Check out the API Guide to see what the badge can do.

Check out this link for an example of using the accelerometer

If you would like to know how hot or humid it is, check the BME680 example from the hatchery. Actually, this tells you about the air pressure, but you can hack it to also display temp and humidity…

4.3.1 - Getting started

Introduction …

The Badge comes with a preinstalled Micropython interpreter. Python should be the easiest way to control the device and write apps for The Badge, especially if you are a beginner or don’t want to spend a lot of time downloading tools and debugging drivers.

First, make sure Python is installed and you didn’t accidentally delete it. Check in the apps menu. If it’s not there: install the Python app from the Hatchery by going to Hatchery -> ESP32 native binaries -> Utility -> Python and install it either onto the flash or onto an SD card.

If you have it already installed, make sure to check that you have the latest version via App update.

There are several ways to run badgepython and develop badgepython applications. None of them are particularly well documented, so it’s up to you to explore what you can do and how to do it in a smart way.

In case you are interested in improving the documentation, we would be very happy to receive pull requests.

Here are a few starting points:

Run Python interactively

Start Python on your badge (apps -> Python). There should be a message on screen that an interactive Python console is availble on your USB serial connection. Baud rate is 115200. Connect to it using a serial terminal of your choice (e.g. screen /dev/tty<your_serial> 115200. On MacOS, your_serial is probably .usbmodem101; on Linux probably ACM0. You may also use other terminal emulators such as PuTTY or picocom based on your OS and/or preference). The badge typically exposes two serial ports, simply try - one should give you access to a terminal. If terminal gives a totally black screen, press enter to see the prompt appear.

“Interactive Python shell now active …”

You can now run python interactively. For example, run print("That was easy!"). Amazing!

$ picocom /dev/ttyACM0 -b 115200
>>> print("That was easy")
That was easy

If you are having problems connecting to the serial console, please check here !

Not only is the terminal a great way to try stuff out, it also allows easy access to The Badge’s file system. Type import os, then os.listdir("/") to see the root filesystem. A FAT partition is mounted on the badge’s internal flash at /. If you inserted a MicroSD card, its contents will be mounted at /sd. You can traverse the directories with os.listdir() (and you will see that Python apps live at /apps/python/<appname>/). You can create and remove directories with os.mkdir and os.rmdir and delete files os.remove. Don’t screw up your filesystem too badly. More documentation on basic micropython’s OS library is available in the MicroPython documentation.

Try using the screen:

>>> import display
>>> display.drawFill(0xFF0000)
>>> display.flush()


display is a badge-specific module. There are several Badge-specific modules. You can find documentation on them api-reference (they might not be all fully up-to-date, but good enough for a start). In addition there is also a mch22 module that offers a few badge-specific APIs. Finding out about it’s features is left as an exercise to the reader (hint: import mch22, dir(mch22)).

Try some of the other APIs

Check in the API Reference for a list of APIs that work on the MCH2022 Badge, Try some of these APIs out in the emulator. Please be aware that you can’t expect APIs to work just because they have a green checkmark. It’s only a suggestion!

Use the mch22 module

There is an mch22 module with a lot of convenience functionality.


The badge has 4 GPIO pins, 2 on the SAO header and 2 more near the prototype area.

Silkscreen LabelRP2040 GPIOMicroPython GPIO
16 (May Contain Hardware)GPIO 16mch22.PROTO_0_PIN
17 (May Contain Hardware)GPIO 17mch22.PROTO_1_PIN
GPIO1 (Shitty Add-On)GPIO 18mch22.SAO_IO0_PIN
GPIO2 (Shitty Add-On)GPIO 19mch22.SAO_IO1_PIN

For example, to turn on a simple led on a Shitty Add-On:

import mch22
mch22.set_gpio_dir(mch22.SAO_IO0_PIN, True)
mch22.set_gpio_value(mch22.SAO_IO0_PIN, True)

Display Brightness

You can set the LCD backlight brightness in 255 steps. 0 is completely off.

import mch22
# 255

Read USB and battery voltages

import mch22
print(f'USB: {mch22.read_vusb():.3f}V    Battery: {mch22.read_vbat():.3f}V')
# USB: 4.868V    Battery: 4.123V

Develop microPython apps in the emulator

Uri Shaked a.k.a Wokwi built an awesome emulation of the badge that runs in your browser. This is an amazing way to quickly get started with app development. It’s not as fast as your badge, but it implements a surprising amount of the peripherals. Just try it.

Run an app on the Badge itself

Have a look at your Badge’s filesystem and the example apps in the Hatchery (btw: browsing the hatchery is a great resource for examples). You will see that each app resides in its own directory /apps/python/<appname>. The main entry point is the script inside that directory. The directory may contain other python sources and resource files. Apps stored in the internal flash reside in /apps/python, apps on the (optional) SD card reside in /sd/apps/python/.

Create an app folder on your Badge’s filesystem (let’s call it /apps/python/myapp in this example). There are two ways to create a new app folder for your app: either connect to the BadgePython interactive shell (screen, PuTTY, …), and create the directory with the os package:

>>> import os
>>> os.listdir("/apps/python")
['citycontrol', 'someapp']

>>> os.mkdir("/apps/python/myapp")

>>> os.listdir("/apps/python")
['citycontrol', 'someapp', 'myapp']

or use the mch2022 tools to create a new folder from your laptop:

$ python /flash/apps/python
Booting into WebUSB, please wait ...
transfer speed: 2.32 kb/s
Directory listing for "/flash/apps/python"...
Directory "citycontrol"
Directory "someapp"

$ python /flash/apps/python/myapp
Succesfully created directory

$ python /flash/apps/python
Booting into WebUSB, please wait ...
transfer speed: 20.32 kb/s
Directory listing for "/flash/apps/python"...
Directory "citycontrol"
Directory "someapp"
Directory "myapp"

Now it’s time to write some code on your laptop using a text editor of your choice. If you’re not sure what and how to program, you can use the following example:

import display
import random

def drawRandomLine():
  x1 = random.randint(0,320)
  x2 = random.randint(0,320)
  y1 = random.randint(0,240)
  y2 = random.randint(0,240)
  color = random.randint(0,0xFFFFFF)

while True:

This program will clear the screen and then draw random lines infinitely.

Save that file as, say,

To upload the file to the Badge, you can clone the mch2022 tools. This repository contains scripts to upload files to the badge via WebUSB.

Python apps reside in the FatFS partitions inside the badge’s internal flash and/or the optional SD card, so you should use the webusb_fat_*** scripts from the tools project. Try python3 tools/ /. You will see that the root directory listing contains two entries: flash and sdcard (the mount points for the internal and external partitions).

$ python3 /
transfer speed: 1045.4196368656173
Directory listing for "/"...
Directory "flash"
Directory "sdcard"

Warning: Confusion. Pandemonium. Chaos!

The paths in the filesystems are different depending on whether you access them internally via the os MicroPython API or whether you adress them externally via the webusb_fat... scripts

Internally, i.e. from MicroPython (or native apps) are prefixed with sd if they are located on the optional SD-Card.

Externally, i.e. from the scripts, paths pointing to internal files are prefixed with flash and paths pointing to the SD Card are prefixed with sdcard. *

¯\ (ツ)

Copy the __init.py__ file.

Call python3 tools/ <file on your laptop> <file on The Badge> to upload your file to the Badge (don’t forget to adjust the path for your laptop). You should see a progress message and a success message on the terminal and your badge screen. If you get a Unicode error, you can probably fix it by changing the fill character in the script (two occurrences).

$ python /flash/apps/python/myapp/
transfer speed: 28560.15516885618
File uploaded

After uploading, you should be ready to launch your app on the Badge (apps -> myapp) and see colourful lines on the screen. If your script contains errors, you will typically see a crash message on screen. To see error messages, connect your serial terminal (see above) to the badge before starting your app.


Be kind, rewind

Unfortunately, there’s no way to end the app yet, so you have to restart your badge by power cycling it (or using the script in the tools folder or uploading another file). Let’s add that by editing your file:

import display
import random
import buttons
import mch22

def reboot(pressed):
  if pressed:


def drawRandomLine():
  x1 = random.randint(0,320)
  x2 = random.randint(0,320)
  y1 = random.randint(0,240)
  y2 = random.randint(0,240)
  color = random.randint(0,0xFFFFFF)

while True:

The additional lines will add a key listener that will trigger a reset when the A key is pressed.

Repeat the upload using the script. Restart your app. Done!

Publish your work!

After you’re done writing an amazing app (and writing an amazing with it), share it with others! The Hatchery is the Badge’s “App store”. You can read about publishing eggs in the hatchery here.

4.3.2 - Neopixels

Accessing the Kite’s neopixels from Python

The kite on the Badge is fitted with 5 neopixels (individually controllable RGB LEDs). They are accessed through the neopixel module.

Here’s an example how to control the LEDs:

# imports
from machine import Pin
from neopixel import NeoPixel

# Pin 19 controls the power supply to SD card and neopixels
powerPin = Pin(19, Pin.OUT)

# Pin 5 is the LED's data line
dataPin = Pin(5, Pin.OUT)

# create a neopixel object for 5 pixels
np = NeoPixel(dataPin, 5)

# turn on power to the LEDs

# set some colors for the pixels (RGB)
np[0] = (255,0,0)
np[1] = (0,255,0)
np[2] = (0,0,255)
np[3] = (255,255,0)
np[4] = (255,0,255)

# send colors out to LEDs

4.4 - RISC-V Playground

If you want to dive into the RISC-V architecture, have a look at the RISC-V Playground.

This projects contains a beginner friendly RISC-V ‘fantasy microcontroller’ for the FPGA featuring a RV32IMC processor and a selection of peripherals:

  • Textmode LCD driver with 7-Bit ASCII font
  • Random number generator
  • GPIO registers for PMOD pin access
  • Timer tick interrupt
  • LEDs
  • UART terminal, 115200 Baud 8N1
  • 1 kb initialised RAM for bootloader
  • 128 kb RAM initialised using file read interface over SPI

Detailed descriptions, memory map and register set are described in the README file.

Docs on RISC-V itself


Clone both the bitstream tools repo

git clone

and the FPGA repo

git clone --recursive

go to the


folder and load both the bitstream for the FPGA and a RISC-V binary: riscv-playground.bin 0xdabbad00:fw/tinyblinky/tinyblinky.bin

Connect to the serial terminal using your favourite terminal emulator with 115200 baud 8N1 LF on ttyACM1.

Get RISC-V assembler

The GNU binutils for RISC-V include the assembler.

Unlike as for the FPGA tools that change rapidly, you can just have a look for binary packages in your distribution.

For Debian 11 Stable “Bullseye”, one gets using

apt-cache search binutils | grep riscv

binutils-riscv64-linux-gnu - GNU binary utilities, for riscv64-linux-gnu target
binutils-riscv64-linux-gnu-dbg - GNU binary utilities, for riscv64-linux-gnu target (debug symbols)
binutils-riscv64-unknown-elf - GNU assembler, linker and binary utilities for RISC-V processors

Both binutils-riscv64-linux-gnu and binutils-riscv64-unknown-elf are fine, but you might have to adjust the actual invocations to the tools depending on which package(s) you actually installed.

Despite the names, these also support 32 bit RISC-V targets.

Example firmware


This one is included into the bitstream for default. It initialises the LCD display and initialises the 128 kb RAM from file “0xdabbad00” using the file read interface over SPI provided by the ESP32 firmware.


A little blinky in RISC-V assembler. A nice “hello world” project.


An example on how to use interrupts on RISC-V, including notes on compressed opcodes and and small tools for printing hex numbers.


Explore the Mandelbrot and Tricorn fractals in ASCII art. This example shows how to use the LCD and buttons in assembler.

Hello GCC

A small project in C featuring serial terminal, buttons, LED and LCD.


This is a port of Mecrisp-Quintus, a 32 Bit Forth implementation, available under GPL3.

For more info, get the full release of Mecrisp-Quintus here:

Useful for debugging, and maybe for you, too.

If you have not used Forth before, better start with this implementation of Forth that comes with much more badge support code.

4.5 - Developing for the RP2040 Coprocessor


RP2040: aka Raspberry Pico. This is an onboard coprocessor that handles two USB <-> serial bridges and acts as an IO extender.

At this point in time, we have no way for the apps to automatically load new firmware to the RP2040 along with their main functionality on the ESP32, but manually flashing a custom firmware using the recovery method is possible, although not recommended.

Should you like to experiment with the RP2040 firmware, its repo resides here.

Install custom firmware

Press SELECT while you’re powering on the Badge, this gets you into RP2 Boot mode:

$ lsusb
Bus 001 Device 019: ID 2e8a:0003 Raspberry Pi RP2 Boot

This causes the USB connection to NOT appear as a serial device (acting as a passthrough to the ESP), but instead as a USB mass storage device (MSD) and will show up like a USB thumb drive.


No fears: The badge is unbrickable, the RP2040 has a hardware-triggered bootloader in ROM and is able to reflash the ESP32. Therefore you can always recover using the USB connection.

Dowload the current known-good firmware image for the RP2040 and copy it into the mass storage folder. Then reset the badge, and you can go on with re-flashing the ESP32 firmware. By the way, has an old certificate on purpose. It is ok.

4.6 - Publishing your App in The Hatchery

WTF is a Hatchery!?

The Hatchery is an app store for The Badge! You can use the Hatchery to publish your own apps and share them with friends. And unlike other App Stores, you don’t need a Dunn & Bradstreet Number, $1000 and don’t have to worry about your app being rejected because it contains malware.

You can also sort through the apps other people have published there. If you do so, please be aware that we don’t check for malware and will NEVER ask for your credit card number or home banking password (just kidding, off course we will.)

BTW, it’s called Hatchery because it (used to) contain “eggs” because previously the Hatchery was limited to Micropython apps and those are called eggs. Knowadays the Hatchery also supports native ESP Apps and FPGA bitstreams.

Installing Apps from the Hatchery.

Probably not a good idea. It’s full of malfware and half finished tutorial apps. It’s much better to write your own app.

If you insist on installing other peoples apps, please have a look at the instructions in the enduser section.

Publishing a Native App in the Hatchery.

First off, we’re having our best UX experts work day and night to tweak the Hatchery Website to make it even easier to use! So expect some of the screenshot to be a bit out of date. Don’t worry, you’ll figure it out.

In case you are experiencing issues regarding 419 Expired errors, try deleting Hatchery cookies from your browser.

Create an Account

Go to and sign up for a new account. Standard stuff, name and password, credit card details …

Create a new Native ESP App

We assume you have an app ready and built. If not, please check out the ESP-IDF App Getting Started tutorial!

Now that you’ve written an app: Find the button to click on to create a new App:

Click on “Eggs” in the top menu

  • Click on “Eggs” in the top menu
  • Click the “add” button
  • Enter your credit card details

Click the “add button”

  • Enter your credit card details

Enter card details

  • and fill out the form. Please select a meaningful category else the whole camp will descend into chaos and noone will be able to find anything. For Type chose “ESP32 native binaries”. Then choose a meaningful and unique name.

Enter App Details

  • Write something in the Description, e.g. “won’t let me submit without a description”, pick a license and off you go.

  • Clicking “Save” may or may not pop up some warning, depending on whether we fixed this. Have I mentioned, that we welcome pull requests? Just go to the github project for the hatchery

  • now you need to upload your app. You should be on the projects detail page which contains a bunch of stuff you can ignore:

    • min and max firmware version
    • Dependencies - this is for Python Apps that need other python apps preinstalled
    • Collaborators - this lists other Hatchery users who are allowed to edit the app details
    • checkbox “Allow to apply fixes to code” if you like other random strangers to poke around in your app to “fix bugs”

More app details!

Ok, now comes the fun part. If you look at the arrows in the screenshot above, you’ll see that a was created for your native app. Don’t need it, click delete (other arrow).

Then there is an “Add icon” button. I don’t think it works. If you want your app to have an icon, create a 32x32 pixel PNG image names “icon.png” and drag onto the large text box with the arrow labeled “drag-n-drop”.

Finally you need to upload the actual firmware. We mentioned the Getting Started Tutorial. We weren’t kidding you’ll actually have to do a stupid tutorial to get a firmware bin to upload. I know … lame. When you’re done, you’ll find the firmware in the build folder. For the tutorial, it should already be called “main.bin”, if not, rename it. In case you’re asking yourself: the *.bin file will be named the same way your firmware project is named in the top level “CMakeLists.txt” file: project(main)


If you are uploading an FPGA project, please name it bitstream.bin.

Once all the relevant stuff is there, click “Save” and if you are feeling brave, check the “Publish” box, this allows others to see your app in the store. As long as you don’t publish, the app won’t show up in The Hatchery, so you can make changes. This is also useful if you plan a second release.

Publish and Save

Your app should now be in the Hatchery!

Woohoo \\o/

and you ought to be able to find it in the Hatchery app on your badge and install it and find it in the “App Launcher” Menu.

installed app

4.7 - Getting Started with TinyGo


TinyGo is an alternative Golang implementation targeted towards constrainted devices such as … The Badge. TinyGo’s creator, Ayke van Laëthem, was kind enough to not only hold a talk about TinyGo at MCH2022 but also write two nice Badge examples and explain how to develop with TinyGo on the Badge.

Install TinyGo

  • Grab the latest release from the TinyGo github and follow the installation instructions for your platform. This needs to be a version > 0.24. In the unlikely event you read this before the release, you can get a special access pre-release of the tools from the CI
  • To build for ESP32, Tinygo requires an xtensa toolchain. This will very likely have been installed on your computer if you have already built a native app. Else you will need to install one. Follow these instructions from Espressif
  • Once you have completed installation, be sure to source the script (or the equivalent) to set all the necessary environment variables. TinyGo needs these to find the xtensa tools

Grab some Demos …

You can download Aycke’s samples from this repo, the Badge example are in directories name ‘mch2022-something’. Go into the relevant directories, read through the examples and finally build and flash them to your Badge using the mch2022 tools

$ git clone
$ cd things/mch2022-leds/
$ tinygo build -o leds.bin -target=mch2022
$ ls
go.mod  go.sum  leds.bin  LICENSE.txt  main.go
$ python webusb_push TinyGoLeds leds.bin

A new app named ‘TinyGoLeds’ will appear in your app menu. When you run it, the LED kite will oscillate in different colors, but the screen will be stuck in the “Starting in App” mode. This is because nothing is being written to the screen.

Let’s fix that. Go into the mch2022-noise example and build it… Stare in awe at the beauty of the Simplex Noise being drawn to the screen!

Simplex Noise

4.8 - ESP Native APIs

There are a number of badge-specific and generic APIs among the components of the template app. This section contains a quick list of the APIs and some notes on using them.

4.8.1 - APIs: Graphics

PAX Graphics is the default way to draw graphics for the MCH2022 badge. Don’t want the getting started? Complete API can be found here.

Getting started

First, download the template app:

git clone my_fancy_app
make install

This will download and install the template app to your badge, showing a colorful “Hello, World!”.

Simply repeat the make install step every time you want to test your app.

To avoid clutter, remove the graphics from the while loop and make a function containing just the graphics code:

// before main ...
// A neat little graphics function.
void my_fancy_graphics() {
    // This fills the screen with blue.
    // Color:              aarrggbb (like #rrggbb but with 0xff instead of #).
    pax_background(&buf, 0xff0000ff);
// in main ...
    while (1) {
        // Call our graphics function.
        // Draw them to the screen.
        // Await any button press and do another cycle.
        // Structure used to receive data.
        rp2040_input_message_t message;
        // Await forever (because of portMAX_DELAY), a button press.
        xQueueReceive(buttonQueue, &message, portMAX_DELAY);
        // Is the home button currently pressed?
        if (message.input == RP2040_INPUT_BUTTON_HOME && message.state) {
            // If home is pressed, exit to launcher.

Note that graphics aren’t immediately shown on screen, this is handled by disp_flush().

Simple HelloWorld

Let’s start by drawing some white text on the blue background:

// A neat little graphics function.
void my_fancy_graphics() {
    // This fills the screen with blue.
    // Color:              aarrggbb (like #rrggbb but with 0xff instead of #).
    pax_background(&buf, 0xff0000ff);
    // This draws white text in the top left corner.
    float text_x     = 0;                   // Offset from the left.
    float text_y     = 0;                   // Offset from the top.
    char *my_text    = "Hello, World!";     // You can pick any message you'd like.
    float text_size  = 18;                  // The normal size for saira regular.
    pax_draw_text(&buf, 0xffffffff, pax_font_saira_regular, text_size, text_x, text_y, my_text);

(The text “Hello, World!” on a blue background.)

Play around with the parameters and see what happens. Try changing text_x and text_y to see where it appears on screen, or maybe change text_font to (for example) pax_font_sky.

Using Images

Using images requires a bit more work, but is still easy to do. First, you must include #include <pax_codecs.h> in each file that decodes PNG images.

Next, find an image that fits in memory (so make it small). Add this to the main folder, next to main.c and include it in CMakeLists.txt:

        # You source files are here, there might be more than just main.c
        # The directories to open header files from are here, again, there might be more.
        "." "include"
        # This is the location of your image.

The EMBED_FILES directive causes the file’s data to be included mostly as if it were a source file. You reference the files like so:

extern const uint8_t image_start[] asm("_binary_my_image_png_start");
extern const uint8_t image_end[]   asm("_binary_my_image_png_end");

This tells the compiler where to find the image. When embedding files, they will always be named in a similiar manner.

Finally, draw the image using pax_insert_png_buf. If your image is located on the SD card or internal filesystem, use pax_insert_png_fd instead.

// A neat little graphics function.
void my_fancy_graphics() {
    // Blue background in case decoding the PNG fails.
    pax_background(&buf, 0xff0000ff);
    // Draws an image, but does not support transformations.
    pax_insert_png_buf(&buf, image_start, image_end-image_start, 0, 0, CODEC_FLAG_OPTIMAL);

(An image of two oranges and an apple.)

If your screen turned blue, then the image may have failed to decode.

Try running make monitor and re-opening the app to see what happened (most likely, the image is too big to fit in memory). To exit make monitor, press CTRL+]

Getting more abstract

Of course, you can do much more than just drawing text! Shown here is an example of drawing a rectangle, a circle and a line:

    // Draw a green circle (position is center).
    //                    color       x   y   radius
    pax_draw_circle(&buf, 0xff00ff00, 60, 60, 20);
    // Draw a transparent red rectangle (position is top left corner).
    //                  color       x   y   width  height
    pax_draw_rect(&buf, 0xb0ff0000, 40, 10, 70,    50);
    // Draw a white line across the entire screen.
    //                  color       x1  y1  x2         y2
    pax_draw_line(&buf, 0xffffffff, 0,  0,  buf.width, buf.height);

(Transparent red rectangle over a green circle on a blue background.)

PAX (the graphics) also supports matrix transformations.

In short, this feature allows you to stretch, resize, rotate and move around drawing. Consider the following example:

    // Save this for later.
        // Modify the translation: shear it.
        pax_apply_2d(&buf, matrix_2d_shear(0.5, 0));
        // This will no longer have a circular shape.
        pax_draw_circle(&buf, 0xff00ff00, 60, 60, 20);
    // Restore the matrix.
    // This will still have a rectangular shape.
    pax_draw_rect(&buf, 0xb0ff0000, 40, 10, 70,    50);

(A warped version of the circle, making it now an elipse.)

Where to Go from Here?

For further details about the library, have a look at the API reference in the library’s repository, robotman2412/pax-graphics

4.8.2 - Board Support Package

Most of the board’s peripherals (RP2040 USB and keyboard coprocessor, ICE40 FPGA, ILI9341 LCD controller, BNO055 accelerometer, BME680 air sensor) are initialized and maintained by the board support package. It does not implement each peripheral’s functions, but it provides initialization functions and accessors to the peripheral instances. The BSP is a separate ESP-IDF component that is supposed to be cloned as a git submodule within your project.

At start of your code:

#include "hardware.h"


esp_err_t err = bsp_init();

There are additional initialization functions for individual peripherals (bsp_rp2040_init() ,bsp_ice40_init(), bsp_bno055_init(), bsp_bme680_init()). Call them prior to use if you intend to use the specific component. The ILI9341 display will always be initialized during startup and therefore does not require separate initialization call.

After initialization, you can use the respective instance accessor functions to obtain the peripheral’s instance, e.g. get_ili9341(), get_rp2040(), get_ice40(), get_bno055(), get_bme680(). See each function’s documentation in hardware.h in the component.

In addition, the BSP package gives you defines to the ESP32 pinout. See mch2022_badge.h.

4.8.3 - WS2812

We all love colorful blinking LEDs, right? There’s a simple API for accessing the five individually addressable RGB LEDs on the Badge’s kite. The API is found inside a separate ESP-IDF compontent ws2812 that is intended as a [git submodule] ( If you started your app development from the [template app] (, it should be already set up.

There’s a sixth RGB LED on the board (next to the top corner of the display). This LED is controlled via the ICE40 FPGA (see its driver for details).

The LEDs are WS2812-compatible. If you’re not already familiar with these LEDs: Each LED contains red, green and blue LED and a tiny controller that receives 24 bit RGB data from a single serial data line. Further data bits are pushed through to its data output, which is connected to the next LED. This allows many LEDs in a string to be individually controlled.

The LED power supply is switched (together with the SD card). Before using the LEDs, set IO19 (GPIO_SD_PWR) to 1.

Before controlling the LEDs, the driver has to be set up with the data line connected to the LEDs (GPIO_LED_DATA). If you want to control other WS2812 LEDs (e.g. connected to one of the extension connectors), you can specify a different value.

Setting the LEDs is pretty straightforward: Set up an array of 15 unsigned brightness values (R,G,B for 5 LEDs).

A minimal example to set all LEDs to red:

  uint8_t red[] = {0,255,0,0,255,0,0,255,0,0,255,0,0,255,0};
  // turn on LED power
  gpio_set_direction(GPIO_SD_PWR, GPIO_MODE_OUTPUT);
  gpio_set_level(GPIO_SD_PWR, 1);
  // initialize WS2812 driver to the appropriate data pin
  ws2812_send_data(red, sizeof(red));

To animate, change the array values and repeat ws2812_send_data in regular intervals.

4.9 - App gallery

If you have made a cool badge app that you want to show, email a picture

4.10 - Rust development for the ESP32

Short description on how to install the tools for Rust development for the ESP32 on the badge

Tools installation

  • Rust toolchain from Follow the instructions given there.
  • If you get an error concerning virtualenv try uninstalling via pip and reinstalling via apt or vice versa …
  • Install cargo-generate (cargo install cargo-generate). If this fails, try just running: rustup update
  • Install the mch2022 webusb tools

Project workflow

  • Create a new project as follows:
$ cargo generate --git cargo
🤷   Project Name : argh
🔧   Destination: /MCH2022/rust-build/rust-esp/argh ...
🔧   Generating template ...
✔ 🤷   STD support · true
✔ 🤷   MCU · esp32
? 🤷   ESP-IDF native build version (v4.3.2 = previous stable, v4.4 = stable, mainline = UNSTA✔ 🤷   ESP-IDF native build version (v4.3.2 = previous stable, v4.4 = stable, mainline = UNSTABLE) · v4.4
? 🤷   Configure project to use Dev Containers (VS Code, GitHub Codespaces and Gitpod)? (bewar✔ 🤷   Configure project to use Dev Containers (VS Code, GitHub Codespaces and Gitpod)? (beware: Dev Containers not available for esp-idf v4.3.2) · false
[ 1/10]   Done: .cargo/config.toml
[ 2/10]   Done: .cargo
[ 3/10]   Done: .gitignore
[ 4/10]   Done: .vscode
[ 5/10]   Done: Cargo.toml
[ 6/10]   Done:
[ 7/10]   Done: rust-toolchain.toml
[ 8/10]   Done: sdkconfig.defaults
[ 9/10]   Done: src/
[10/10]   Done: src
🔧   Moving generated files into: `/MCH2022/rust-build/rust-esp/argh`...
💡   Initializing a fresh Git repository
✨   Done! New project created /MCH2022/rust-build/rust-esp/argh

$ cd argh
  • Generate an app image using:
# Tell Rust which toolchain to use (you only need to do this once ...)
$ rustup override set esp
info: override toolchain for '/home/<YOUR_USER_NAME>/projects/MCH2022/rust-build/rust-esp/argh' set to 'esp'

# set some environment variables, so rust knows where to find its tools:
# you will probably want to save this in a little 'source' scriptlet ...
export PATH="/home/<YOUR_USER_NAME>/.espressif/tools/xtensa-esp32-elf-gcc/8_4_0-esp-2021r2-patch3-x86_64-unknown-linux-gnu/bin/:/home/<YOUR_USER_NAME>/.espressif/tools/xtensa-esp32s2-elf-gcc/8_4_0-esp-2021r2-patch3-x86_64-unknown-linux-gnu/bin/:/home/<YOUR_USER_NAME>/.espressif/tools/xtensa-esp32s3-elf-gcc/8_4_0-esp-2021r2-patch3-x86_64-unknown-linux-gnu/bin/:$PATH"
export LIBCLANG_PATH="/home/<YOUR_USER_NAME>/.espressif/tools/xtensa-esp32-elf-clang/esp-14.0.0-20220415-x86_64-unknown-linux-gnu/lib/"

# finally, build the image ...
$ cargo espflash save-image ESP32 rust_esp.img                     
    Updating index      
  Downloaded filetime v0.2.17     
  Downloaded env_logger v0.9.0
  Downloaded libloading v0.7.3
	... literally download the _entire_ entire internet ...
	... argh
  • Upload the image using web USB:
$ --run rust rust_esp.img

A more elaborate example.

You can find a more elaborate example that drives the display a shows a nice rust screensaver in The Hatchery and on github.

I’ve been told there is some magic involved to grab control of the screen

Rust Graphics


These instructions use the esp-idf as provided by Espressif so you won’t have access to the components added by the It’s probably possible to use the version provided by the, but I have not tried this.

Also: this seems to work on some computers and not on others … Please feel free to provide a PR to the documentation or a link to a sample app … Make sure you’re using the newest version of everything. Throw away your computer and by a Windows one …

4.11 - Using Arduino to Develop Badge Apps



Introduction to Arduino

The ESP32 on the badge can be programmed using the Aduino IDE.

  1. Install the Arduino IDE if you haven’t already.
  2. Install ESP32 support using these instructions
  3. Install PyUSB for Python 3 using pip or the package manager provided by your distro. On Debian you can run sudo apt install python3-usb
  4. Download mch2022-tools

Now write your Arduino sketch as usual, by selecting the ESP32 wrover module. But instead of uploading your sketch, use Sketch > Export compiled binary (ctrl+alt+s)

Now you need to plug in the badge, turn it on, and launch from the mch2022-tools repo with the path of the binary that Arduino generate in your sketch folder.

python path/to/ "my cool app" path/to/my_app.ino.esp32.bin --run

After a few seconds your app should be running on the badge.

Controlling the display

The easiest way to control the display is by using the Adafruit ILI9341 library. Go to Tools > Manage Libraries... and search for the Adafruit GFX library and the Adafruit ILI9341 library and install both. Include them as follows

#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"

#define PIN_LCD_CS 32
#define PIN_LCD_DC 33
#define PIN_LCD_RST 25

Adafruit_ILI9341 tft = Adafruit_ILI9341(PIN_LCD_CS, PIN_LCD_DC, PIN_LCD_RST);

And then add the following lines to the setup function.


And now you can use regular GFX commands like so:

tft.setCursor(0, 0);

Controlling the LEDs

The LEDs are controlled using the FastLED library, which can once again be installed from the library manager.

First define and include all the things.

#include <FastLED.h>

#define PIN_LED_DATA 5
#define PIN_LED_ENABLE 19
#define NUM_LEDS 5


And then run the following setup code:

FastLED.addLeds<SK6812, PIN_LED_DATA, GRB>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);

// This has to be placed after SPI (LCD) has been initialized (Arduino wants to use this pin as SPI MISO...)
digitalWrite(PIN_LED_ENABLE, HIGH);

And you can now just set the LED colors as follows:

        leds[i] = CRGB::Purple;

Reading the buttons

The buttons are controller by the RP2040, and can be read over I2C. Here is a simple example.

#include <Wire.h>

#define PIN_I2C_SDA 22
#define PIN_I2C_SCL 21
#define PIN_RP2040_INT 34

#define RP2040_ADDR 0x17  // RP2040 co-processor
#define BNO055_ADDR 0x28  // BNO055 position sensor
#define BME680_ADDR 0x77  // BME680 environmental sensor

#define RP2040_REG_LCD_BACKLIGHT 4
#define RP2040_REG_INPUT1 0x06
#define RP2040_REG_INPUT2 0x07

void set_backlight(uint8_t brightness) {

uint16_t read_inputs() {
    Wire.requestFrom(RP2040_ADDR, 4);
    uint16_t input = | (<<8);
    uint16_t interrupt = | (<<8);
    return interrupt;

void setup() {
  Wire.begin(PIN_I2C_SDA, PIN_I2C_SCL);
  pinMode(PIN_RP2040_INT, INPUT);

uint8_t brightness = 0;
void loop() {
    if (!digitalRead(PIN_RP2040_INT)) {
      Serial.println(read_inputs(), BIN);

A full list of all the registers can be found here

Reset the ESP32

Restting the ESP32 can be done using the following snippet.

#include <esp_system.h>
#include "soc/rtc.h"
#include "soc/rtc_cntl_reg.h"

void return_to_launcher() {

You can now trigger this when the home button is pressed like so:

if (!digitalRead(PIN_RP2040_INT)) {
    if (read_inputs() & (1<<0)) {