With the increasing popularity of amateur rocketry, there is a growing need for reliable, compact live telemetry systems capable of real-time apogee detection, recovery support, and flight data acquisition.

This work presents the student-led design, development, and testing of a custom printed circuit board intended for use in high-performance model rocketry applications. The avionics board was developed with the objective of achieving reliable, real-time flight data acquisition, apogee detection, and telemetry transmission, all within the constraints of a compact, lightweight, and low-power architecture. Throughout the development cycle, particular attention was placed on sensor selection, telemetry reliability, and software flexibility, ensuring the final system could serve as a robust platform for both experimental and operational rocketry missions.

The avionics board incorporates three core sensors: the ADXL375, a high-g accelerometer; the MS8607, a compact environmental sensor capable of measuring pressure, temperature, and humidity; and the BNO055, a 9-DOF inertial measurement unit capable of reporting low-g acceleration, absolute orientation (in both quaternions and Euler vectors), and gravity vectors. These sensors were selected for their precision, small form factor, and compatibility with the flight dynamics encountered in amateur and research-level rocketry. The ADXL375 and BNO055 provide high-bandwidth data critical for detecting dynamic transitions such as burnout and apogee, while the MS8607 enables barometric altitude tracking.

The board operates on CircuitPython, chosen for its rapid prototyping capabilities, code readability, and ease of field modification. This decision significantly accelerated development, allowing for modular testing of individual subsystems such as sensor integration, power management, and flight logic. A core function of the avionics system is to detect apogee in real time and flag the event for downstream actions such as telemetry transmission or recovery system deployment. Multiple apogee detection algorithms were evaluated, relying on pressure gradient reversal and vertical acceleration zero-crossings, with fail-safes incorporated to reduce false positives caused by tilt-over events.

Telemetry is broadcast at 433 MHz using a lightweight LoRa RF module. Antenna configurations were tested to optimize signal strength, focusing on helicoid and quarter-wavelength monopole antennas. Both were evaluated for their radiation patterns, size constraints, and resilience to variability in mounting positions. The system includes logging capabilities, buffering data in onboard memory during telemetry loss to ensure no critical data is missed during key flight events.

The final design, dubbed SprinkleMini, was produced through a complete hardware manufacturing cycle, including schematic design, PCB layout, and hand assembly. The board is currently in the testing phase, with bench tests and early field trials confirming the reliability of sensor readings and telemetry output under operational conditions. Lessons learned from this testing have informed improvements for future revisions, including software enhancements.

This avionics platform lays the groundwork for future embedded systems in rocketry and aerospace prototyping, with potential deployment in missions requiring detailed atmospheric profiling, real-time tracking, and autonomous flight event detection.