To make it easier, we listed all the interfaces used by the Rover as default. Just to make sure you don't interfere with them when developing.
to power the board and Raspberry Pi
hExt pin 1 (I/O)
to control the battery LED (to show the system readiness)
hMot A, B, C & D (PWM H-bridge)
to power the Rover motors and encoders
used to flash firmware to the board (doesn't need to be connected all the time)
Take into consideration during the Rover assembly and development.
The board corner where there's power connector and power-related components tends to interfere with sensitive electronics such as wheel encoders. Make sure the encoder cables don't run on top of the corner.