stm32-simple-imu-reading

Stream IMU (and optional magnetometer) data over UART as a compact binary packet. Two ready-to-run targets are provided: an STM32 Nucleo-L476RG and an Arduino Nano. Both targets share the same pure-C sensor driver library and produce an identical packet format, so the same host-side receiver works with either board.

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Repository structure

stm32-simple-imu-reading/
├── arduino/
│   └── arduino_nano_imu/          # Arduino sketch + all driver files (copy here to build)
│       ├── arduino_nano_imu.ino   # main sketch — sensor selector at the top
│       ├── imu_hal.h / imu_hal.c  # IMU abstraction layer
│       ├── mag_hal.h              # magnetometer abstraction layer
│       ├── mpu6050_drv.h/c
│       ├── mpu9250_drv.h/c        # includes AK8963 via I2C bypass
│       ├── icm42688_drv.h/c
│       ├── lsm6dso_drv.h/c
│       ├── ism330dhcx_drv.h/c
│       ├── icm20948_drv.h/c       # includes AK09916 via I2C master
│       ├── lis3mdl_drv.h/c
│       ├── mmc5983ma_drv.h/c
│       ├── qmc5883l_drv.h/c
│       └── hmc5883l_drv.h/c
└── stm32/
    └── stm32-imu-stream/          # STM32CubeIDE project (NUCLEO-L476RG)
        └── Core/
            ├── Inc/
            │   ├── sensor_config.h    # ← one-stop sensor selection
            │   ├── serial.h
            │   ├── imu/               # driver headers
            │   └── mag/               # magnetometer driver headers
            └── Src/
                ├── main.c
                ├── serial.c
                ├── imu/               # driver sources
                └── mag/               # magnetometer driver sources

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Supported sensors

IMU (accel + gyro)

Sensor	Interface	Built-in mag	Default I2C address
MPU-6050	I2C	—	0x68
MPU-9250 / MPU-9255	I2C	AK8963 (bypass)	0x68
ICM-42688-P	I2C	—	0x68
LSM6DSO	I2C	—	0x6A
ISM330DHCX	I2C	—	0x6B
ICM-20948	SPI (STM32) / I2C (Arduino)	AK09916	—

Standalone magnetometers (optional, paired with any IMU that has no built-in mag)

Sensor	I2C address
QMC5883L	0x0D
HMC5883L	0x1E
LIS3MDL	0x1C / 0x1E
MMC5983MA	0x30

All sensors run at 3.3 V. Do not connect VDD or I2C lines directly to a 5 V supply or 5 V logic — this will permanently damage the sensor.

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Packet format

Both targets send the same 20-byte binary packet over UART at 115200 baud:

Bytes	Content	Type
0	0xAA header	—
1	0xFF header	—
2–3	Accel X	int16, little-endian
4–5	Accel Y	int16, little-endian
6–7	Accel Z	int16, little-endian
8–9	Gyro X	int16, little-endian
10–11	Gyro Y	int16, little-endian
12–13	Gyro Z	int16, little-endian
14–15	Mag X	int16, little-endian (zeros if no mag)
16–17	Mag Y	int16, little-endian
18–19	Mag Z	int16, little-endian

Raw counts are sent — no scaling applied. Convert using the sensor's sensitivity from its datasheet (e.g. for MPU-9250 at ±4 g: accel LSB = 8192 counts/g).

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STM32 quickstart (NUCLEO-L476RG)

1. Select your sensor

Open stm32/stm32-imu-stream/Core/Inc/sensor_config.h and uncomment exactly one IMU:

// #define SENSOR_MPU6050
#define SENSOR_MPU9250
// #define SENSOR_ICM42688
// #define SENSOR_LSM6DSO
// #define SENSOR_ISM330DHCX
// #define SENSOR_ICM20948

If using a standalone magnetometer alongside an IMU that has no built-in mag, uncomment one of:

// #define MAG_LIS3MDL
// #define MAG_MMC5983MA

The host bus is selected automatically:

• ICM-20948 → SPI2 (PA9 = CS, PB13 = SCK, PB14 = MISO, PB15 = MOSI)
• All others → I2C1 (PB8 = SCL, PB9 = SDA)

2. Adjust I2C address if needed

Still in sensor_config.h, check the address for your sensor (AD0/SA0 pin strapping):

#define MPU9250_I2C_ADDR  0x68   /* AD0=GND → 0x68; AD0=VCC → 0x69 */

3. Build and flash

Open the project in STM32CubeIDE, build, and flash via the on-board ST-LINK.

4. Receive data

Open any serial terminal (or your own host application) at 115200 8N1 on the ST-LINK virtual COM port. Packets arrive at 100 Hz (TIM4 interrupt).

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Arduino quickstart (Arduino Nano)

1. Select your sensor

At the top of arduino/arduino_nano_imu/arduino_nano_imu.ino, uncomment exactly one:

//#define SENSOR_MPU6050
 #define SENSOR_MPU9250
// #define SENSOR_ICM42688
// #define SENSOR_LSM6DSO
// #define SENSOR_ISM330DHCX
// #define SENSOR_ICM20948

If adding a standalone magnetometer, uncomment one of:

// #define MAG_QMC5883L
// #define MAG_HMC5883L
// #define MAG_LIS3MDL
// #define MAG_MMC5983MA

2. Wiring

Arduino Nano pin	Sensor pin
3.3 V	VDD / VCC
GND	GND
A4 (SDA)	SDA
A5 (SCL)	SCL

The Arduino Nano runs at 5 V. Power sensors from the 3.3 V pin only and add I2C level shifters on SDA/SCL to avoid damaging 3.3 V sensors with 5 V logic. Boards that run at 3.3 V natively (Arduino Nano 33, STM32 Nucleo, etc.) do not need level shifters.

3. Upload

Open the sketch folder in Arduino IDE, select Arduino Nano (ATmega328P), and upload.

4. Receive data

Open Serial Monitor at 115200 baud or read packets from your host application. Packets arrive at approximately 100 Hz (delay(4) at the end of loop()).

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Gyro calibration

Both targets run IMU_CalibrateGyro() on startup (100-sample average). Keep the board stationary for about one second after power-on while the gyro bias is being measured.

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Hard-iron magnetometer calibration

Raw magnetometer values include a hard-iron offset that shifts the X/Y/Z readings by a constant amount. To calibrate:

1. Stream data while slowly rotating the sensor through all orientations.
2. Find the min/max of each axis; bias = (max + min) / 2.
3. Pass the biases to MAG_SetBias() in the setup section:

MAG_SetBias(MAG_HANDLE, bias_x, bias_y, bias_z);

MAG_ReadCorrected() subtracts these values automatically on every read.

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Driver architecture

All sensor drivers are built on two thin abstraction layers:

• imu_hal.h — imu_handle_t with vtable (init, read_raw, set_accel_range, …)
• mag_hal.h — mag_handle_t with vtable (init, read_raw, …)

Drivers are pure C with no HAL dependencies. They receive read, write, and delay function pointers at init time, so the same driver files compile unchanged for STM32, Arduino, or any other platform.

To port to a new platform, implement three callbacks:

int8_t my_i2c_read (uint8_t reg, uint8_t *buf, uint16_t len, void *ctx);
int8_t my_i2c_write(uint8_t reg, const uint8_t *buf, uint16_t len, void *ctx);
void   my_delay_ms (uint32_t ms);

then call the appropriate XXX_HandleInit() and IMU_Init().