So I am looking at creating a second RPI/Arduino that would connect to my Navio2 and that from command from the Navio2 it would take a sensor reading and log it. My question is I can not find a lot of information on connecting a second device to the Navio2 and how I would be able to send communication and commands to it. My goal would be to use a Ground Control Software like Mission Planner to send a command to the Navio2 that would send the command to the sensor package through something like UART.
So I guess my questions are:
Is it possible to attach a second Device (RPI/Arduino) to the Navio2 and send commands through either UART or one of the USB ports to the second device and how would I go about sending commands from Mission Planner to Navio2 to RPI?