Trying to debug why the magnetic sensor of my MPU9250/6500 won't connect to my Raspberry Pi 4+

[TheOtherRealm]

I am trying to debug why the magnetic sensor of my MPU9250/6500 won't connect to my Raspberry Pi 4+, but all the other sensors will. I did a bad soldering job on my first one of these sensors and it just wouldn't connect. I got two new ones though and both of them are detected and give the 0x68 address and work except for the magnetic sensor (if I comment out self.configureAK8963(self.mfs, self.mode), I don't get any errors).

So. my question is, is it possible I just have two bad solders that give the same error message or is it a software problem?

I can't see any problems with the physical unit:

Code

import sys
sys.path.append('/home/tor/robot/MPU-9250-Sensors-Data-Collect/MPU-9250-Sensors-Data-Collect/mpu9250_jmdev')
from registers import *
from mpu_9250 import MPU9250
import time
import logging
##################################################
# Create                                         #
##################################################
mpu = MPU9250(
    address_ak=AK8963_ADDRESS, 
    address_mpu_master=MPU9050_ADDRESS_68, # In 0x68 Address
    address_mpu_slave=None, 
    bus=1, 
    gfs=GFS_1000, 
    afs=AFS_8G, 
    mfs=AK8963_BIT_16, 
    mode=AK8963_MODE_C8HZ)
##################################################
# Configure                                      #
##################################################
mpu.configure() # Apply the settings to the registers.
##################################################
# Show Values                                    #
##################################################
while True:
    print("|.....MPU9250 in 0x68 Address.....|")
    print("Accelerometer", mpu.readAccelerometerMaster())
    print("Gyroscope", mpu.readGyroscopeMaster())
    print("Magnetometer", mpu.readMagnetometerMaster())
    print("Temperature", mpu.readTemperatureMaster())
    print("\n")
    time.sleep(1)

Results

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 97, in configure
    self.configureAK8963(self.mfs, self.mode)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 233, in configureAK8963
    self.writeAK(AK8963_CNTL1, 0x00, 0.1)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 1013, in writeAK
    self.bus.write_byte_data(self.address_ak, register, value)
  File "/usr/local/lib/python3.8/dist-packages/smbus2/smbus2.py", line 458, in write_byte_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 121] Remote I/O error

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 97, in configure
    self.configureAK8963(self.mfs, self.mode)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 233, in configureAK8963
    self.writeAK(AK8963_CNTL1, 0x00, 0.1)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 1013, in writeAK
    self.bus.write_byte_data(self.address_ak, register, value)
  File "/usr/local/lib/python3.8/dist-packages/smbus2/smbus2.py", line 458, in write_byte_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 121] Remote I/O error

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "sensorTest.py", line 13, in <module>
    mpu.configure() # Apply the settings to the registers.
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 102, in configure
    self.configure(retry - 1)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 102, in configure
    self.configure(retry - 1)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 105, in configure
    raise err
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 97, in configure
    self.configureAK8963(self.mfs, self.mode)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 233, in configureAK8963
    self.writeAK(AK8963_CNTL1, 0x00, 0.1)
  File "/usr/local/lib/python3.8/dist-packages/mpu9250_jmdev/mpu_9250.py", line 1013, in writeAK
    self.bus.write_byte_data(self.address_ak, register, value)
  File "/usr/local/lib/python3.8/dist-packages/smbus2/smbus2.py", line 458, in write_byte_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 121] Remote I/O error

If I put try/except blocks around smbus2.py (ioctl(self.fd, I2C_SMBUS, msg)), I can get data for the other three sensors:

|.....MPU9250 in 0x68 Address.....|
Accelerometer [-1.210205078125, -8.0, -8.0]
Gyroscope [43.9453125, -1.373291015625, -21.270751953125]
[OSError(121, 'Remote I/O error'),
 <smbus2d.SMBus object at 0xffff8d0f20a0>,
 12,
 3,
 7,
 None]
Magnetometer [0.0, 0.0, 0.0]
Temperature 24.258753407014705

What the offending function looks like:

    def read_i2c_block_data(self, i2c_addr, register, length, force=None):
        """
        Read a block of byte data from a given register.

        :param i2c_addr: i2c address
        :type i2c_addr: int
        :param register: Start register
        :type register: int
        :param length: Desired block length
        :type length: int
        :param force:
        :type force: Boolean
        :return: List of bytes
        :rtype: list
        """
        if length > I2C_SMBUS_BLOCK_MAX:
            raise ValueError("Desired block length over %d bytes" % I2C_SMBUS_BLOCK_MAX)
        self._set_address(i2c_addr, force=force)
        msg = i2c_smbus_ioctl_data.create(
            read_write=I2C_SMBUS_READ, command=register, size=I2C_SMBUS_I2C_BLOCK_DATA
        )
        msg.data.contents.byte = length
        try:
            ioctl(self.fd, I2C_SMBUS, msg)
        except Exception as e:
            if hasattr(e, 'message'):
                print(e.message)
            pprint([e, self, i2c_addr, register, length, force])
        return msg.data.contents.block[1:length + 1]

The sensor is readable and is detecting the correct address:

tor@tor:~/robot$ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --        

Thanks!

[campagnani]

The voltage of the VCC pin cannot exceed 3.6v. If that happens you can fry the chip. (Source)

Maybe you plugged in 5v and fried the magnetometer chip, so it doesn't show up at the i2c address.