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PCA9554: gpiod tools report remote i/o error whereas i2c-tools work

Severin Mutter
Prodigy 20 points

Part Number: PCA9554

Dear TI Support Team

We have some systems where we see an issue with “gpioget”. The I2C IO Expander is connected to I2C2 and the gpiod tools normally work. Now when we add a different I2C device over a cable to the I2C bus (with a different address), we see that the gpioget command sometimes works and sometimes does not work:

$ gpioget 4 0

gpioget: error reading GPIO values: Remote I/O error

$ gpioget 4 0

0

When communicating with the Expander directly with the i2c-tools, we do not see any communication issue.

$ sudo i2cget -y -f 2 0x21

Any idea what could be the issue and how we can solve it?

Our OS is ubuntu 24.04 LTS and the kernel version is 6.8, the platform is the NVidia AGX Thor.

Thank you for your help.

  • 0
    Guru 326180 points

    When i2cget works, then the hardware works correctly.

    The gpioget tools goes through the GPIO subsystem, which then ask the I²C device; the i2cget tool goes directly to the I²C bus. So it appears that there is something wrong with the GPIO configuration.

    I do not know what exactly "remote I/O error" means. You could check with an oscilloscope if the I²C master actually tries to do a read transaction.

  • 0
    TI__Guru 63858 points

    Hi Severin,

    Do you have an o-scope capture of the SDA and SCL pins for this issue?

    Regards,

    Tyler