Raspberry Pi SPI
The Raspberry Pi SPI Serial Peripheral Interface is very neatly laid out on the GPIO P1 connector as shown above. There are the three main SPI pins: MOSI P1-19, MISO P1-21, SCK P1-23.
In addition there is also CE0 P1-24 and CE1 P1-26 pins which are used to select the slave devices. These pins are also sometimes called Chip Select (CS), and even Slave Select (SS). The Raspberry Pi SPI interface can therefore have a maximum of two slave devices connected to it.
Author: Peter J. Vis