In order for devices to communicate, whether they are computers or microcontrollers, there needs to be a method for communication. In our previous guide on I²C and Pico, we've briefly talked about digital communication protocols.

Serial Peripheral Interface (SPI) is a synchronous serial communication protocol that is widely used between microcontrollers and peripheral ICs such as sensors, displays, flash memory, real-time clocks, shift registers, ADCs, DACs, etc. In this guide, learn about the SPI communication protocol and use it with a shift register and Pico! After completing this guide, you will know how to get 8 outputs out of just 3 GPIO pins.