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IMU setup

imu_sdk reads IMU data from MPU-family devices over USB serial: 6-axis (MPU6050/6500/6886) or 9-axis (MPU9250/9265 + AK8963 magnetometer), on any ESP32 or M5StickC board. Firmware streams JSON at ~100 Hz; all variants run at 115200 baud.

Board / moduleChipAxesFirmware
M5StickC Plus 1.1MPU68866firmware/m5imu_firmware/
Generic ESP32 + MPU6050/6500MPU6050/65006firmware/esp32_mpu/ (IMU_HAS_MAG 0)
Generic ESP32 + MPU9250/9265MPU9250/9265 + AK89639firmware/esp32_mpu/ (IMU_HAS_MAG 1)

Flashing firmware​

M5StickC Plus 1.1: install the Arduino IDE + M5Stack board package (https://m5stack.oss-cn-shenzhen.aliyuncs.com/resource/arduino/package_m5stack_index.json) and the M5StickCPlus library, open firmware/m5imu_firmware/m5imu_firmware.ino, select board M5Stick-C-Plus, and upload. The LCD shows Hz, temperature, and Z-axis gyro bias once running.

Generic ESP32: install the Arduino IDE with the esp32 board package (no extra libraries needed beyond Wire), open firmware/esp32_mpu/esp32_mpu.ino, and edit the config block at the top:

#define IMU_HAS_MAG  0      // 0 = MPU6050/6500 (6-axis), 1 = MPU9250/9265 (9-axis)
#define IMU_ADDR     0x68   // 0x68 when AD0 low, 0x69 when AD0 high
#define IMU_SDA      21
#define IMU_SCL      22
#define LED_PIN      2      // heartbeat LED (-1 to disable)

Wiring: VCC→3.3V, GND→GND, SDA→GPIO21, SCL→GPIO22, AD0→GND (address 0x68). For MPU9250, leave the PS pin floating or pull it low for I2C mode.

Python side​

pip install -e /path/to/imu_sdk   # or: pip install -e . from that directory
from imu_sdk import ImuReader

with ImuReader("/dev/ttyUSB0") as reader:   # or ImuReader() to auto-detect
    for sample in reader:
        print(sample.accel(), sample.gyro(), sample.temp)

find_port() auto-detects the serial port; a callback/background-thread form (reader.start(callback)) is also available for integration into a control loop like m5teleop's.

Gyro bias calibration​

Both firmware variants auto-calibrate gyro bias at boot: keep the device still for ~2.5 s while it averages 500 samples, then subtracts that per-axis bias from every subsequent reading. Moving the device during this window produces a wrong bias estimate and visible drift — power-cycle and try again.

ImuData.pitch/roll/yaw are always 0.0 — the firmware no longer computes orientation; that's done host-side by m5teleop's ESKF (see Teleoperation control loop, step by step).

6-axis vs. 9-axis​

The 9-axis magnetometer data (mx, my, mz) is decoded when present but not currently used by the teleop pipeline's attitude estimate — the ESKF corrects yaw drift via ZARU (zero angular-rate updates) at rest, not a magnetic heading reference. sample.has_mag reports whether it's available on your board.