CM5-RPI-CM4-IO use Pin 3 & Pin 5 for I2C?

#1

I’m using an RPI CM4 baseboard with my CM5, and would like to use the 40-pin GPIO header pin 3 & pin 5 for I2C (the standard for the RPI). How do I go about doing this?

Thanks!

#2

I’ve figured it out, but in case someone else is looking to do the same…

GPIO2 and GPIO3 is typically SDA1 and SCL1 respectively on the Raspberry Pi 40 pin expansion bus. However, these pins are not available on the CM5 in any configuration. However, if you swap SCL and SDA, and enable the I2C6_M0 overlay, it’ll work fine.

So, connect SCL to GPIO2 (pin 3 on the 40 pin header) and SDA to GPIO3 (pin 5 on the 40 pin header). This is swapped from a “normal” RPI 40 pin header.