@rob-biernat which M5Stack or Stick are you using?
The M5Stacks and Sticks have an I2C grove port (port A) but this is also a digital I/O port in that it can read or write 0 or 1 values (on or off) I am currently triggering a relay unit from the port.
The M5Go base has has 2 additional port which are multi I/O (port b) and UART (port C) Unlike Arduinos, the esp32 which powers the M5Stack has no set pin functions and all pins can be used for a range of functions.
When using Port A Yellow is SCL (pin 22) and white is SDA (pin 21) and need to be defined.
I have started to document the different functions of the grove connector and you can find them on pg 19 and 20 of my WIP book here https://github.com/Ajb2k3/UIFlowHandbook/blob/master/UIHB1404192.pdf