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Thread: Cannot see I2C device

  1. #1

    Default Cannot see I2C device

    I am using the Silicon Labs CP2112EK eval kit. It's a USB-SMBUS/I2C device.
    When I boot into Ubuntu, I can see this device no problem, it's in /dev/i2c-x
    On the exact same server with a different boot drive, using openSUSE Leap, I do not see any i2c device in /dev

    i2c-tools is installed on both machines but I don't think I'm even at the stage where I can use this yet if I don't see anything in /dev. I have a 2nd server also with Ubuntu (16) and it also has no problem seeing this i2c device.

    Is there anything I have to enable in openSUSE to get this to show up? The openSUSE server has no issue seeing other USB devices I plug in. I imagine the sensors package should use this too but it did not help.

  2. #2

    Default Re: Cannot see I2C device

    I installed openSUSE Tumbleweed just to check. I do not see /dev/i2c-x either.
    However, when I run sensors-detect, I eventually get to:

    Next adapter: CP2112 SMBus Bridge on hidraw0 (i2c-1)
    Do you want to scan it? (YES/no/selectively):
    Adapter doesn't support all probing functions.
    Some addresses won't be probed.


    So I guess it is actually on /dev/hidraw0 but how do I get i2cdetect to interact with this? Seems like sensors-detect knows something else, that it is i2c-1 (which is what I was expecting) so how can I point other applications to this? And is there any way to force it to probe addresses? I do need to grab it and verify.

  3. #3

    Default Re: Cannot see I2C device

    I think it is fixed now.
    The issue seems to be i2c_dev module is not loaded by default. The sensors-detect loads the module and then unloads it when done, hence the confusion. Also it does not seem to properly modify the necessary files so that the device is seen on boot the next time around.

    The fix is just to force the module to load at boot. There are so many conflicting instructions and methods floating around the 'net. The easiest and clearest set of instructions comes from SUSE: https://www.suse.com/documentation/s..._modprobe.html

    I'm glad it's done. Usually my experience is the other way around. It just works in openSUSE and I have to fight to get Ubuntu to work.

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