The Cyber Ægg is a low-power LoRa badge built around a Nordic nRF52840 microcontroller. The design goal is to run for the entire week of BornHack on a single battery charge, so a lot of care goes into keeping the power consumption down in both hardware and firmware.
The full KiCad design is open source at Ranzbak/bornhack2026-hardware.
Prototype
At the time of writing the design is still at prototype stage. Some of the RF circuits (NFC, LoRa, Bluetooth) still carry U.FL / IPEX connectors to make tuning easier, and the on-PCB antennas are not yet fully characterised. Consider this design beta — do not order your own boards yet.Overview
| Component | Part | Interface |
|---|---|---|
| Microcontroller | Nordic nRF52840 | — |
| Display | 1.54" black/red/white e-paper, 152 × 152, SSD1675 / SSD1675B controller | SPI |
| LoRa radio | Semtech SX1262 | SPI |
| Bluetooth Low Energy | nRF52840 built-in radio | — |
| NFC | nRF52840 NFC tag PHY + on-PCB coil | — |
| Expansion | QWIIC (I²C) connector | I²C |
| Input | 5-way joystick + Execute / Cancel buttons | GPIO |
| Feedback | RGB LED, piezo buzzer | GPIO / PWM |
| Power | Li-ion battery, USB-C for power and data | — |
Display
The badge uses a 1.54 inch tri-colour (black / red / white) e-paper display with a resolution of 152 × 152 pixels, driven by an SSD1675 / SSD1675B controller. E-paper keeps the badge readable in bright camp sunlight and draws no power to hold an image, which is a big help for the week-long battery goal.
Manual input
Because the Cyber Ægg is inspired by the 90’s Tamagotchi egg-shaped toy, the buttons carry the same names:
| Button | Function |
|---|---|
| Select | Navigate through the menu options |
| Execute | Start the option under the cursor |
| Cancel | Cancel the current operation |
To make navigation more intuitive, the Select button is implemented as a 5-way joystick with a press action.
Bluetooth
Bluetooth Low Energy is provided directly by the nRF52840. It operates in the 2.4 GHz band and uses an on-PCB antenna based on a Texas Instruments reference design (included in the standard KiCad 9 library). See the TI application note SWRA228 for details.
LoRa
Long-range connectivity is provided by a dedicated Semtech SX1262 radio with the matching/balun circuit specified in the Semtech application note AN1200.54. The LoRa antenna is a Texas Instruments design documented in SWRA416. On the network side the badge speaks MeshCore, so it can join the wider camp mesh out of the box.
NFC
The nRF52840 includes an NFC PHY, used here to drive a resonant circuit consisting of an on-PCB coil (roughly 2.8 µH) and tuning capacitors, forming a tank circuit matched to 13.56 MHz. The nRF52840 only supports tag functionality (not reader mode), which the firmware uses for location-based games and station taps.
QWIIC
The badge carries a QWIIC connector — a standardised I²C connector used by a large range of SparkFun and third-party breakout boards. Two 10 kΩ pull-up resistors are fitted on the board, and the nRF52840’s internal pull-ups can be enabled as well when the bus capacitance is high.
Power
The badge is powered by a Li-ion battery and charged over USB-C. Bluetooth is disabled while USB is connected to keep the charging path simple, so unplug the badge when you want to pair with the MeshCore app.