This is a very simple C-based transmit-only UART, good for low speeds up to 4800 baud when used with a 1MHz clock.
The intent of this is to provide a simple console output for debugging code on small ATTiny-series microcontroller, but in theory should work on any AVR chip.
The only requirements are a single GPIO pin that will serve as the transmit out.
The code is 100% C code and requires no interrupts or timers. As such, it
might be prudent to call cli() before these routines and restore interrupts
with sei() later as the code is not guaranteed to behave if interrupts steal
too much CPU time.
Usage is pretty simple. The configuration settings are set in uartcfg.h.
Adjust these for your project, and in your code, include uart.h.
Call uart_init() somewhere in your hardware initialisation, and you should
be set to send short strings to the UART for debugging purposes.