Thanks for the responses. Individual MCUs will be mounted on the same board, same plane, with one exception. One of the MCUs will be located perhaps 1-3 meters (several feet) away from the Master Controller, and be routed through a somewhat electrically noisy environment.

I'm intending for a single Master with all other MCUs configured as polled Slaves.

The I2C protocol seems like it's suitable so far. I'm just unclear on how much "work" is done manually with software and how much occurs in the background with hardware. The PBP3 Manual lists I2CREAD/WRITE commands, but states they are software driven and don't rely on I2C hardware.