OSError: [Errno 19] ENODEV

Repro Steps

Initialize the bus and U171

i2c0 = I2C(0, scl=Pin(33), sda=Pin(32), freq=100000)
print(i2c0.scan())
imupro_0 = IMUProUnit(i2c0)

i2c0.scan() returns BMI270 (0x68) and BMP280 (0x76); the BMM150 is behind the BMI270.

Trace for the constructor's failure is :

Traceback (most recent call last):
  File "main.py", line 24, in <module>
  File "main.py", line 17, in setup
  File "unit/imu_pro.py", line 36, in __init__
  File "driver/bmi270_bmm150.py", line 720, in __init__
  File "driver/bmi270_bmm150.py", line 539, in __init__
  File "driver/bmi270_bmm150.py", line 622, in _write_reg
OSError: [Errno 19] ENODEV

Looking at the underlying code :

Constructor calls:

super().__init__(i2c, address=bmi270_address, aux_address=address)

Which does a soft reset, then attempts to write a register:

# Perform initialization sequence.
# 0.Soft-reset
self.soft_reset()

# 1.Disable power save mode.
self._write_reg(PWR_CONF, 0x00)
time.sleep_ms(10)

The write fails:

self._i2c.writeto_mem(self.address, reg, val)

I patched the following and added i2c0.scan() after each i2c write:

IMUProUnit.soft_reset
IMUProUnit._write_reg
IMUProUnit.new_write_burst

Scanning the bus after each write, stops the ENODEV error. However init never completes.

Any ideas how to get U171 to work?