A3 Beacon and Eggs

Hardware design files (KiCad 9) for the A3 recovery beacon — a VHF transmitter stitched to the main recovery shock chord.

Boards

Beacon_and_eggs/ — V1 (fabricated)

40 × 80 mm, 4-layer (F.Cu / GND / PWR / B.Cu).

• MCU — STM32F411CEU6 with 25 MHz and 32.768 kHz crystals, SWD header, boot/reset circuits, and test points
• Radio — SA868S / SA818V VHF module, UART control at 9600 baud, with TX_EN and TX_PWR_DN control lines and a TX audio input
• Sensor — ADXL343 accelerometer on I²C (ALT ADDRESS tied high → 0x1D)
• Power — BQ24070 Li-ion charger, USB-C input with ESD clamps, MIC5528 3.3 V LDO, NTA4151P / NTA4153N load switches, and a divider for battery voltage monitoring on the ADC
• Antenna — plated mounting holes serve as the RF feed and ground clamp for a fabric antenna.
• Status LEDs, battery connector, and an interactive BOM under bom/

Beacon_and_eggs_V2/ — in progress

A condensed second revision. Planned:

• Moved to low frequency LoRa Module with Semtech's SX1278
• Move to a smaller Battery
• PIC MCU to interface with transmitter

WIP

Beacon BNC Adapter PCB/

Two-connector coax breakout, used to attach a standard antenna or analyzer to the beacon's bare antenna pads for bench testing.

Firmware

Lives in the separate A3_Beacon_and_Eggs_FW repository (STM32CubeMX + HAL). It is bring-up code only, written to check that the V1 hardware works - it reads the accelerometer's ID register, handshakes with the SA868S, and blinks out which of the two responded.