How to interface various IMU sensors with STM32 via I2C or SPI?

Using IMU sensors (Inertial Measurement Units) with STM32 microcontrollers is a common practice in robotics, drones, motion tracking, and navigation systems. Here’s a practical guide on interfacing various IMU sensors with STM32 via I2C or SPI, and how to process their data.

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Popular IMU Sensors and Interfaces

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Steps to Interface IMU with STM32

1. Hardware Setup

• Connect SCL/SDA (for I2C) or SCK/MISO/MOSI/CS (for SPI) to STM32 pins.

• Use pull-up resistors (4.7kΩ typical) for I2C.

• Power with 3.3V (check datasheet!).

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2. STM32CubeMX Configuration

• Enable I2C1 or SPI1 in CubeMX.

• Set appropriate GPIOs for communication.

• Generate code using HAL drivers.

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3. Reading Data (Example: MPU6050 via I2C)

c

#define MPU6050_ADDR  (0x68 << 1)
#define WHO_AM_I      0x75
#define ACCEL_XOUT_H  0x3B

uint8_t check, data[14];

// Check device ID
HAL_I2C_Mem_Read(&hi2c1, MPU6050_ADDR, WHO_AM_I, 1, &check, 1, HAL_MAX_DELAY);

// Read raw accel and gyro data
HAL_I2C_Mem_Read(&hi2c1, MPU6050_ADDR, ACCEL_XOUT_H, 1, data, 14, HAL_MAX_DELAY);

int16_t ax = (data[0] << 8) | data[1];
int16_t ay = (data[2] << 8) | data[3];
int16_t az = (data[4] << 8) | data[5];

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4. Data Conversion

Each IMU has a sensitivity scale. Example for MPU6050:

c

float accelX = ax / 16384.0; // if FS = ±2g
float gyroX = gx / 131.0;    // if FS = ±250 °/s

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5. Sensor Fusion (Optional)

To combine accelerometer, gyroscope, and magnetometer data into orientation angles, use:

• Complementary Filter (simple, fast)

• Kalman Filter (complex, accurate)

• Madgwick/Mahony algorithms (open source)

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Tips

• Use interrupts for real-time motion detection.

• For accurate angles, integrate gyro data and correct drift with accelerometer/magnetometer.

• Consider RTOS (FreeRTOS) for multitasking sensor reads and processing.

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Driver Options

• Use ready-made libraries (e.g., from ST, Bosch, or Arduino ported drivers).

• Or write a custom driver by reading sensor datasheets and using HAL functions.