====== SPI ======
SPI requires the following pins:

  * SCK, to synchronize devices
  * MOSI/COPI, for data transfer from the master to the slave
  * MISO/CIPO, for data transfer from the slave to the master
  * SS/CS (one for each slave), for selecting a slave to communicate with

Though it varies by chip manufacturer, the general process is to pull the desired CS pin low, perform a transfer, and set CS high again. In the Arduino SPI library, these steps should be surrounded by ''SPI.beginTransaction()'' and ''SPI.endTransaction()''. 

===== Resources =====
  * https://www.gammon.com.au/forum/?id=10892

{{tag>electronics protocol}}