Foldable Electronic Device for Shooting Sports

This project involves a portable, foldable electronic device designed for shooting sports and training applications. The system detects supersonic projectiles passing through a target plane by capturing their shock wave. It uses eight high-bandwidth MEMS microphones (digital I2S output, 80 kHz frequency range) arranged in a diamond/plus-shaped mechanical frame. By precisely measuring the arrival time differences (TDOA) of the shock wave at each microphone, the system calculates the projectile’s speed and its exact intersection point with the sensor plane. This point is then projected onto a virtual target to determine the hit coordinates, score, and hit/miss status. All results are transmitted wirelessly (LoRa or WiFi) to a mobile device or scoreboard in real time.

System architecture:

8 satellite microphone PCBs, each housing one digital I2S MEMS microphone, mounted at fixed positions on a foldable frame.

Two STM32 microcontrollers on the main board — each reads four synchronized I2S microphone channels and performs real-time pulse detection and accurate time-of-arrival estimation.

One ESP32 microcontroller serves as the central controller: it collects timestamp data from both STM32 units, runs the TDOA-based localization algorithm (including temperature compensation), and manages wireless communication (WiFi + LoRa).

Environmental sensor (BME280) for temperature/humidity correction of the speed of sound.

Battery-powered with a rechargeable Li-Po cell and power management.

What needs to be done:

Mechanical design (foldable diamond frame, enclosures, microphone mounts)

Electronics design (schematics & PCB layout for satellite boards and the main board)

Firmware for the STM32s (multi-channel I2S DMA, shock-wave detection, sub-sample time interpolation)

Firmware for the ESP32 (TDOA solver, hit projection, WiFi/LoRa communication, calibration)

System integration and validation