AN_4300
Title:
AVR307: Half Duplex UART Using the USI Module on tinyAVR and megaAVR devices
Description:
The Universal Serial Interface (USI) present in 8-bit AVR devices like the ATtiny26, ATtiny2313, and ATmega169, is a communication module designed for TWI and SPI communication, but can also be used for UART communication as well.
