Payload Core

Firmware for the rocket payload flight controller, responsible for fin actuation, flight data acquisition and logging.

System Overview

The payload core can be run on the STM32F411Xe family of microcontrollers, though the configuration is designed for the smaller STM32F411CE variant, found on the blackpill.

The pin assignments, and system interface assignments are as follows:

Component	Model	Interface	Description	Pins
Fin Servos 1/2	FS5106B-FB	PWM (TIM1_CH1/2)	Active fin control	CH1(PA8), CH2(PA9)
Fin Servos 1/2	FS5106B-FB	ADC1 (CH8/9)	Feedback	CH8(PB0), CH9(PB1)
SPI Flash	Various	SPI1	Onboard storage for inflight logging	SCK(PA5), MISO(PA6), MOSI(PA7)
SD Card	-	SPI2	To facilitate data recovery	SCK(PB10), MISO(PB14), MOSI(PB15)
Altimeter	BMP388	SPI3	Barometric pressure/altitude sensing (altitude in feet)	SCK(PB12), MISO(PB4), MOSI(PB5)
IMU	LSM9DS1	SPI4	6-DOF inertial measurement (Mag disabled)	SCK(PB13), MISO(PA11), MOSI(PA1)
-	-	UART2	Serial output	TX(PA2), RX(PA3)
-	-	RCC	Onboard LSE/HSE	OSC32_IN(PC14), OSC32_OUT(PC15), OSC_IN(PH0), OSC_OUT(PH1)
-	-	SWD	Serial Wire Debug port	SWCLK(PA14), SWDIO(PA13)
-	-	TIM2	System Tick	-
-	-	TIM3	Blink Tick	-
-	-	TIM4	Fin Tick	-

The pin configuration is set up as follows:

Additionally, for the pins setup as GPIO, the definitions are as follows:

Pin	Peripheral	Direction
PB2	SPI2 CS	Output
PA4	SPI1 CS	Output
PB3	SPI3 CS	Output
PB6	SPI4 CS IMU	Output
PA0	Onboard KEY	Input
PC13	Onboard LED (Blackpill)	Output

Getting Started

Prerequisites

• PlatformIO (CLI Core or IDE)
• On Windows machines: ST-Link drivers

Building

You can use the PlatformIO IDE GUI to build and flash this project.

If using PlatformIO Core:

# Build the project
pio run

# Build and upload
pio run --target upload

Development

The project uses the STM32Cube HAL framework. Key configuration options are in platformio.ini.

Initialization functions were generated by STM32CubeMX. The project file for that is located in the repository root. Should one need to change initialization configs, copy and paste the differences rather than overwriting files.

Adding Drivers

Place driver libraries in the lib/ directory. Each library should have its own subdirectory with source files and headers, as such:

lib/
├── sensor123/
│   ├── sensor123.c
│   └── sensor123.h
└── motor456/
    ├── motor456.c
    └── motor456.h

Clock Configuration

The system is configured to use the external oscillators (HSE/LSE) with the following configuration:

• System Clock: 100 MHz from PLL
• RTC Clock: 32.768 KHz direct from LSE
• AHB/APB1/APB2/etc.: All clocks @ 100 MHz, except APB1 Peripheral, which is 50 MHz