SPI

Watch this video link.

The SPI port has a bunch of settings that the bus pirate can let you control. The first one is the speed. SPI is not like I2C. It is synchronous and sends out its own clock and this is what governs the speed. SPI is full duplex meaning that reading and writing happens at the same time over two seperate data lines.

It is a master-slave protocal where all communication is initiated by the master. Addressing is done through a dedicated slave select line to to each peripheral.

SPI Lines are:

• MISO - Master In Slave Out
• MOSI - Master Out Slave In
• SCL - Serial Clock Line
• SS - Slave Select Line (for every peripheral)

A quick about SPI is that because it is a synchronous full duplex master/slave bus, data can transfer can only be initiated by the master, including when the master wants the slave to talk. This is why master has to send dummy bytes of data when reading bytes back from the slave.