This document discusses three common protocols for serial communication: USART, SPI, and I2C. USART is described as the simplest way to establish a connection between an AVR microcontroller and a computer or another microcontroller. The document then provides an example of using USART serial communication to transmit an 8-bit binary number representing the state of a button press from one microcontroller to another.
2. Three protocols
USART
SPI
I2C
USART: Simplest way to establish a connection between an AVR
microcontroller and a computer (or another microcontroller).