I'm using a Raspberry Pi 4 - Rev1.4 together with a tc9548 multiplexer and 2 additional I2C sensors behind each multiplexer channel.

OS version:

AME="Raspbian GNU/Linux" VERSION_ID="11" VERSION="11 (bullseye)" VERSION_CODENAME=bullseye ID=raspbian ID_LIKE=debian HOME_URL="http://www.raspbian.org/" SUPPORT_URL="http://www.raspbian.org/RaspbianForums" BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

Linux musselv5 5.10.63-v7l+ #1488 SMP Thu Nov 18 16:15:28 GMT 2021 armv7l GNU/Linux

The wiring diagram roughly looks as follows, the cables are not super short but I don't think they are the error source: enter image description here

I receive a remote I/O error for around 40-50% of the measurements I conduct. It is almost ok since I am constantly measuring but I don't think that's the correct way to use the I2C of the RPI for long-term.

How can I reduce the rate of a remote I/O error?

[Errno 121] Remote I/O error
  • You will need to post the code you are using that produces this error if you want anyone to diagnose it and suggest a solution.
    – goldilocks
    Jan 14 at 15:38
  • Error 121 is I2C newbie's favourite. For trouleshooting, try (1) use only one sensor, (2) shorten all wires to less than 30cm, (3) remove on board pull up (usually 4kt or 10k smd. (4) Ref: stackoverflow.com/questions/62757687/…
    – tlfong01
    Jan 15 at 2:04