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This code originated from Martin Thomas' AVR-Projects page. It's licensed under a BSD-style license. My intent is to extend this code for my own projects and possibly provide an Arduino port.

Timer-based AVR Software-UARTS

Some AVRs do not have a hardware-UART others have one or two. In case a UART is needed on "non-UART" AVRs or the available hardware-UARTS are not enough to fullfill the project-needs a software-UART can be used. The software-UART available here is based on the "gerneric software uart" by Colin Gittins which can be downloaded from the iar.com website in the application-notes section. I have ported/adapted this code to AVRs using avr-gcc/avr-libc and fixed some smaller mistakes. This code does not need an external interrupt-pin for the RX-line - any input-pin will do. But the RX pin gets sampled three times the baudrate so more process-time is needed compared to an "external-int" approach as presented in various Atmel Application-Notes.

Get the latest version of this "softuart-library" including a demo-application here (timestamp 20101010).

Version History:

  • 20070319: fixed handling of start- and stopbit in receiver-section, code-cleanup, extended example-applciation
  • 20070430: added more configuation options for easier adaption to other AVRs, this time tested with an ATtiny85
  • 20101010: different minor modifications, included settings for ATmega164(P|PV|PA), ATmega324, ATmega644

Copyright (c) 2003, Colin Gittins
Copyright (c) 2005, 2007, 2010, Martin Thomas
All rights reserved.

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