Abstract: The serial protocol is used to display a multitude of information, and is often an indispensable aid that developers use on MCUs (microcontrollers) for debugging purposes. The ATtiny85 is a small device with a limited number of pins that has no standard serial module. This paper gives a high-level overview of the serial protocol itself, and presents code, with analysis, that can be used on an ATtiny85 to transmit data to a serial device. The code is designed to be easy to understand and conservative in its use of variable and program space. It is not aggressively optimised, though. The resulting code is less than 100 lines long, and is available online.
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