Sentinel Data Logger (SDL)

Design Goal

SDL is designed to act as a rocket data logger, tracking pressure, acceleration , rotation, and magnetic fields. This version lacks both GPS and a radio link, but an expansion port is planned to allow later installation of both features.

It also has both a micro SD card (post flight bulk logging) and SPI flash chip (in flight logging).

Firmware

Programmed using the STM32CubeIDE, SDL was initially supposed to simply read the sensors and save to flash, but I quickly discovered how much more involved this needed to be. Currently the board uses individual drivers for each onboard IC to handle the low level control and a handful of subsystem managers to provide higher level control of features like logging radio and and battery management. The next step is to refine the drivers and add state estimation.

First Launch

To date this board has flown three times, once on an F27 motor and twice on F52 motors. During launch it experienced roughly 14g acceleration on the F52 motors and upwards of 30g+ on landing (a small parachute was chosen as a stress test) and has not only survived both times, it also was able to successfully log each flight.

Ground Infrastructure

While currently very simple I have plans of designing and building a unified ground station to allow me to talk with any of my future rocket systems. But for the time being its just a breadboard with a Lora radio. Its simple but effective.

Posts

What SDL’s First Flight Data Taught Me

The first SDL flights were not about proving a finished avionics system. They were about getting real data from a rocket, validating the basic hardware and firmware, and finding out what needed to improve next. At this stage, SDL was still closer to a debug data logger than a polished flight computer. That was intentional. The goal was to get the board into a real flight environment, collect enough useful data to understand what happened, and use that data to guide the next v

SDL’s Packet System

SDL is built around a simple idea: collect useful flight data, store it reliably, and make it easy to analyze after the flight. That sounds straightforward, but the data has to move through several different paths. During development, USB serial output is useful because it gives immediate feedback. During flight, onboard flash is the priority because it can store data directly on the board. After flight, SD card export makes the data easy to retrieve. LoRa telemetry adds a li

SDL Firmware Architecture

SDL started as a rocket data logger, but even a basic flight data logger quickly becomes more complicated than just reading a sensor and printing values. The board has multiple IMUs, barometers, GPS, magnetometer, power monitoring, onboard flash, SD card storage, USB output, LoRa telemetry, status LEDs, and a buzzer. Each device has its own setup process, communication bus, timing requirements, and failure modes. If all of that code lived directly in the main loop, the firmwa

Justin Michaud