Geeetech 6 socket IDC SPI Shield connect SPI devices to Arduino The IDC Shield allow us to connect SPI devices to Arduino. It contains a 6-pin IDC socket and a SPI socket. A Serial Peripheral Interface (SPI) system consists of one master device and one or more slave devices. The master is defined as a microcontroller (Arduino) providing the SPI clock and the slave as any integrated circuit receiving the SPI clock from the master. Easy to use and high cost effective.