Firmware for the Karca Engine Control Box

Project status

This project will not be a part of Eclipse's future mission control plans. It's being refactored as a personal project.

Improvement Scope

firmware performance + additional features

• Replace the external ADC (plus the SPI polling interface) with DMA using the internal ADCs of the STM32F429/F407 MCU

• Replace HAL with the LL drivers (less code bloat hopefully)

• Log data in binary format instead of expensive csv

• Replace the websocket interface with a simpler tcp socker (no need to integrate with quonkboard anymore)

• Stretch objective: Ethernet bootloader for wireless firmware updates

hardware

• Use the stm32f429 for development instead of the stm32f207 (More RAM, FPU for FIR filtering)

• replace the MCP3208 external ADCs with the STM32's internal ADCs

repo structure

• discard the cube ide dump and replace with just the necessary source files, linker scripts, ioc files, toolchain etc.

The original project objectives are listed below (To be archived)

Overview

This repository contains the STM32Cube IDE project with the firmware running on the STM32F407 controller for Proxima's Engine Control Box. The code aims to fulfil the same objective as slonk and RESFET. These are as follows:

• Collect Data from the sensors and relay it to the operator over TCP at a minimum rate of 10Hz
• Receive Commands from the operator over TCP and actuate the corresponding valves/ignition relay
• Support a faster sampling rate (up to 5kHz) during ignition

Motivation

The engine control firmware was written (yet again!) as part of the team's move away from the Raspberry Pi-based system and towards a microcontroller. The reasons for the switch are as follows:

• Deterministic sampling and actuation. The STM32 uses a real-time operating system that reduces the timing uncertainty during data collection and valve actuation
• Wider range of peripherals. The STM32 has three SPI peripherals and three 12-bit internal ADCs, which provide more headroom for expansion in case more sensors are needed
• Low power consumption

However, if future members decide to move back to the Raspberry Pi, they are strongly recommended to reuse and adapt the slonk engine control software.

Installation

Install STM32CubeIDE and STM32CubeMX

Clone the repository git clone https://github.com/rice-eclipse/mc-firmware

Open STM32CubeIDE and set the root directory of the repository as the workspace

Build projects/websocket_rtos to build the code for the current development version of the software running on the F207 Nucleo board

Run the code using the GUI

Hardware Stack

• MCU: STM32F407 (ARM Cortex-M4 CPU)
• Sensors: Thermocouples, Load Cells, Pressure Transducers
• Sensor Interface 12-bit, 8 channel MCP3208 ADC (SPI interface)
• Wireless Communication Websocket connection over LwIP (Lightweight IP TCP implementation)

Software Design

The system is divided into isolated tasks managed by the FreeRTOS scheduler:

1. Data Reading
   • Processes raw data from the ADCs and stores it in a shared buffer.
2. Command Handling
   • Processes incoming commands from the Ground Station.
3. Data Sending
   • Writes flight data to SD Card for onboard storage.
   • Transmits real-time data via WebSocket to the Ground Station Dashboard (Quonkboard) at a decimated interval.

Relevant files

The following files are found in projects/websocket_rtos/Core/Src

1. main.c
   • Entry point into the program
   • Initializes all the peripherals
2. freertos.c

• Application code: contains all the tasks for the program

3. interface.c
   • Provides a wrapper around hardware drivers and helper functions that rely on FatFS
   • Allows the user to run the program without an SD card by setting the appropriate preprocessor directive TEST_LOGIC
4. utils.c

• contains the hardware drivers and helper functions for the main application

Development Environment

• Language: C
• OS: FreeRTOS