The GrovePi is stacked on top of the Raspberry Pi. There is no need for any other connections. Communication between the two occurs over the I²C interface. All Grove modules connect to the universal Grove connectors on the GrovePi+ shield via the universal 4 pin connector cable.
The Grove modules work on analog and digital signals, they connect directly to the ATmega328 microcontroller on the GrovePi+. The microcontroller acts as an interpreter between the Raspberry Pi and the Grove sensors. It sends, receives, and executes commands sent by the Raspberry Pi.
The GrovePi+ is compatible with Raspberry Pi 3, 2, 1B+, 1B, A+.
Please note: The Raspberry Pi board is not included.