Device Tree • Re: RPi5 dtoverlay i2c-fan fails with i2c-path parameter

Yes, it should work fine with i2c2 on Pi 5 provided the pins are suitable for your application:

Code:

Usage:  dtoverlay=i2c2-pi5,<param>=<val>

Good evening,

I believe my configuration questions are resolved and wanted to thank you again as well as document my solution.

Yes, the i2c2-pi5 overlay is working. It nicely creates an i2c2 bus and those devices can be accessed via i2c requests.
However, I had trouble using that i2c2 bus as a target for another dtoverlay with the command line dtoverlay command or the config.txt dtoverlay directive.

This is failing for both of my devices on i2c2. (command line version shown below, the config.txt version also did not work for me.)There were no such issues on i2c1, i2c3, or i2c5... I suspect dtoverlay is intentionally unaware of the i2c2 target, perhaps a holdover from the pre-RPi5 usage of i2c2.

The solution that did work was using the full device tree path to i2c2 in my config.txt as shown here:

dtoverlay=mcp23017,addr=0x20,noints,i2c-path=/axi/pcie@120000/rp1/i2c@78000

Just using a ,i2c2 target did not work on either the command line or the config.txt. This may not be ideal, perhaps a bit hack-ish. I'll work with it for now... it's progress.

Thanks again,
TJ

Statistics: Posted by tjsmith — Wed Jan 22, 2025 4:29 am

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