Read ICM-20948 IMU sensor via I2C

Discussion in 'UDOO KEY' started by marcoanto, Apr 14, 2023.

  1. marcoanto

    marcoanto New Member

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    Hello,

    I have received my UDOO KEY, I try to read ICM-20948 sensor via I2C form both microcontroller (RP and XX) with Micropython.
    When I try to query the sensor on the I2C bus by requesting the device ID, I always get an unexpected value (see attached image).
    ICM-20948_I2C.png

    I can't read the sensor register properly. where am i wrong?

    Saluti
     
  2. DrewTChrist

    DrewTChrist UDOOer

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    Notice that, only for kickstarters, the IMU sensor has been changed and is currently installed the model MPU-6500, a 6-axis motion tracking sensor.

    This notice is in the docs. Different sensor entirely. Maybe this is causing your issue.
     
  3. marcoanto

    marcoanto New Member

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    Thank you!
    I missed the notice,I was referring to the schematics!
    Now it work, the right sensor is MPU6500
     
  4. xbrav

    xbrav UDOOer

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    Just adding some extra information for if you want to talk to it on the 2040:

    from machine import Pin, I2C
    from time import sleep

    bus = I2C(1, scl=Pin(3), sda=Pin(2), freq=400000)
    print(bus.scan())
    print(bus.readfrom_mem(105, 117, 1))

    This will return both the I2C address (105 decimal, aka 0x69 hex) and the WHOAMI info ( b'p' or 0x70 hex) to confirm the MPU6500. P4 (labelled as I2C) on the board will need to have pins 1 and 2 jumpered (the dot will indicate Pin 1).
     
  5. pdblood

    pdblood UDOOer

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    Hi, when I try this I get an error:

    >>> from machine import Pin, I2C
    >>> bus = I2C(1, scl=Pin(3), sda=Pin(2), freq=400000)
    >>> print(bus.scan())
    [105]
    >>> print(bus.readfrom_mem(105, 117, 1))
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    OSError: [Errno 5] EIO

    Any idea what could be going wrong? I have a jumper connected to pins 1 and 2 of the P4 jumper (labeled I2C).
     
  6. pdblood

    pdblood UDOOer

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    UPDATE: Accessing the MPU6500 from the ESP32 with the standard I2C micropython library works perfectly, but I have to use the SoftI2C micropython library for it to work on the RP2040.

    On ESP32:
    >>> from machine import Pin, I2C
    >>> bus = I2C(1, scl=Pin(21), sda=Pin(18), freq=400000)
    >>> print(bus.scan())
    [105]
    >>> print(bus.readfrom_mem(105, 117, 1))
    b'p'


    So there is nothing wrong with I2C on the ESP32, and nothing wrong at all with the MPU6500 module.

    I tried re-flashing the latest stable micropython firmware on RP2040 (v1.20), and even tried flashing the latest micropython nightly build for Rpi Pico, but I still got the same error as before trying to read from the MPU6500 using the RP2040.

    Finally, I tried using the SoftI2C micropython library on the RP2040, which does NOT use the native I2C hardware, and this worked.

    On RP2040:
    >>> from machine import Pin, SoftI2C
    >>> bus = SoftI2C(scl=Pin(3), sda=Pin(2), freq=400000)
    >>> print(bus.scan())
    [105]
    >>> print(bus.readfrom_mem(105, 117, 1))
    b'p'


    So, apparently something is wrong with the hardware supporting I2C on RP2040. I guess I can just use SoftI2C, but this puts the burden of I2C on the RP2040 processor. Any thoughts on anything else to try here?
     
  7. Opi-Van-Kristovi

    Opi-Van-Kristovi New Member

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    I'm using Arduino IDE, but am struggling with the same problem.
    After I found a working library for the sensor, it was pretty straightforward to get the sensor data output with the ESP32. But I haven't yet found a way to get this to work with the RP2040. But then again, I have no prior experience with the RP2040
     
  8. cyberlmt

    cyberlmt New Member

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    Fortunately I have been able to communicate with the MPU using the methods described above, but I have a question. What does the I2C peripheral ID value of 1 in the micropython I2C() function represent? Does it indicate which I2C bus is being used? I can't find this ID documented anywhere nor have I been able to puzzle it our from the Udoo Key schematics or the MPU6500 docs. I'd really like to know!
     

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