What is SPI?
From : https://blog.digilentinc.com/what-is-spi/
A question I asked myself a couple of months ago that I am glad to answer now! After an introduction to SPI protocol, I will show an example of SPI protocol signals using the Analog Discovery 2, WaveForms, and a PmodALS.
SPI is an acronym for Serial Peripheral Interface. Okay, so what is that? It is one form of electronics communication protocol: how something like a microcontroller (or some “master” device) can send/receive data from external electronics like sensors, shift registers, and SD cards (called “slave” devices) over a short distance.