AVR Software UART Tx

AVR UART Tx in software for ATtiny series

--by Captdam @ 2022-10-23 07:41 GMT

Why software UART Tx

Recently I was working on a project using ATtiny series MCU. The ATtiny series MCU has smaller footprint than ATmega series MCU, making it favored for small applications. However, the ATtiny series MCU lacks the hardware communication modules. An USI module is used as a half-software half-hardware solution for SPI or I2C communication. For UART, there is no hardware UART support on ATtiny series (atleast for all ATtiny in PDIP package), except the ATtiny 2313 MCU.

For my application, using a ATmege MCU is not an option, because it is too big for my PCB. Using the new core-idependent AVR is not possible due to lack of programer. Therefore, I have to come with a software UART solotion.

Fast UART Tx

For some application, only transmitter is required. The MCU acts like a beacon device, it only sends data to external device but does not receive data from external device.