Minerva II Flight Computer Firmware

Overview

This project provides the firmware for the Minerva II flight computer, a system designed for high power rockets (HPR). It manages sensor data acquisition, pyro channel control, state estimation, data logging, flight event detection, and data transmission autonomously during flight.

Written in C++ and built on top of the Arduino framework, the firmware is designed to run on a Teensy 4.1 inserted into a Minerva II sensor and power integration board with a focus on real-time responsiveness and reliability.

---

Features

• Sensor Integration:
  • Accelerometer, gyroscope, magnetometer, barometer, GPS
  • Sensor fusion via the Madgwick AHRS filter for orientation and a Kalman filter for altitude estimation
• Energetics Control:
  • Support for multiple pyro channels with firing logic and continuity sensing
• Flight State Detection:
  • Detection of arming conditions
  • Apogee detection and timed parachute deployment
  • Flag-based state machine
• Data Logging:
  • SD card logging with actively managed buffer for performance
  • Dual-format output: binary and serial (for debugging)
• Communications:
  • Serial communication over UART or USB for live telemetry and command reception
  • Packet integrity verification using CRC32
• Command Interface:
  • Serial-triggered events

---

Key Components

main.cpp

• Main control loop
• Initializes all subsystems: sensors, state logic, logging, pyro channels
• Uses interrupts to handle real-time sensor updates
• Manages serial command handling and packet transmission

Pyro Class (pyro.cpp/.h)

Handles:

• Firing pyrotechnic devices via GPIO
• Monitoring continuity with sensors
• Bitwise encoding of pyro status into a telemetry packet

Sensors Class (Sensors.h)

Wraps multiple sensors and provides calibrated readings:

• Accelerometer & Gyroscope: via BMI088
• Magnetometer: MMC5983MA
• Barometer: BMP581
• GPS: u-blox M10S

Supports:

• Rotation correction via quaternion math
• Soft/hard iron calibration for magnetometer
• Continuous sensor polling using SPI/I2C

Note: The actual implementation of the sensor interface probably should not have been put in the .h file, but it works and so I never touched it -SP

State Class (state.cpp/.h)

Implements the state machine for flight logic:

• Uses a bitmask (uint16_t) to store states, each bit in the 2-byte int represents a different flag
• Arming logic based on altitude, velocity, acceleration, and time
• Apogee detection via velocity near zero
• Time-delayed deployment of drogue and main parachutes

Kalman Filter (kf.h)

Provides basic 3-state Kalman filtering to estimate:

• Position (altitude)
• Velocity
• Acceleration

Used to smooth noisy barometer and accelerometer readings.

Logging Class (logging.cpp/.h)

Manages:

• SD card initialization and file creation
• Logging packet structures
• Buffering to optimize SD writes
• Also prints packets for debugging purposes

structs.h

Defines key data structures:

• minerva_II_packet: Telemetry and logging packet
• state_packet: Encodes flight state and related timestamps

---

Build & Run

Requirements

• Arduino-compatible microcontroller (Teensy, STM32, etc.)
• Arduino IDE or PlatformIO
• Required libraries:
  • BMI088, BMP581, MMC5983MA, u-blox GNSS
  • Quaternion, BasicLinearAlgebra, MadgwickAHRS
  • SdFat, FastCRC
• See: platform.ini for relevant dependency URLS

Upload

Use the Arduino IDE, Teensy Bootloader, or Platform IO to upload main.cpp and ensure board configuration matches your hardware.

---

Serial Commands

During flight or testing, you can trigger events using serial commands:

Command	Action
P0H	Fire pyro channel 0
P1H	Fire pyro channel 1
P2H	Fire pyro channel 2
P3H	Fire pyro channel 3
CAM	Turn on camera (via P0)
FUL	Increase radio packet rate
SAV	Decrease radio packet rate

All commands use a CRC32 checksum and must be sent in the format:

0x44 0x55 <CMD (3 bytes)> <CRC32 (4 bytes)>

---

State Flags

The flight logic uses a 16-bit bitmask for space efficient state tracking:

Bit	Flag
0	ARMED
1	REACHED_ARMING_ALTITUDE
2	REACHED_ARMING_VELOCITY
3	REACHED_ARMING_ACCELERATION
4	REACHED_ARMING_DELAY
5	REACHED_APOGEE
6	FIRED_DROGUE
7	FIRED_MAIN
8	FIRED_SUSTAINER (future)

---

Developer Notes

• Data Synchronization: Sensor reads and state updates are handled on interrupt triggers to maintain time-aligned data.
• Failsafe Handling: SD card retries on failure; GPS reinitializes on timeout.
• Timekeeping: Uses elapsedMicros and elapsedMillis from Teensy framework.

---

Authors

• Shivam Patel — [email protected], RPL 2021-2025
• Carlton Wu — [email protected], RPL 2021-2024

---

License

© 2021-2025 Rutgers Rocket Propulsion Lab. All rights reserved.