History

Andrew Makousky 600f120c85 RTC: Use open-drain signaling on 1SEC too.		2020-11-25 01:08:03 -06:00
..
test	RTC: Use open-drain signaling on 1SEC too.	2020-11-25 01:08:03 -06:00
.gitignore	Testing improvements.	2020-09-12 15:11:53 -05:00
MacRTC.c	RTC: Use open-drain signaling on 1SEC too.	2020-11-25 01:08:03 -06:00
Makefile	Finished test bench implementation, fixed firmware bugs found during	2020-09-10 05:07:27 -05:00
README.md	RTC: Program fuse bits from C source.	2020-09-17 02:46:49 -05:00

README.md

RTC

This directory contains a fully functional firmware for implementing a drop-in replacement for the RTC on ATTiny85 microcontroller. Unfortunately, ATTiny85 cannot be a true drop-in replacement, but you can get pretty close. The main caveat is time drift due to counting seconds entirely from the internal oscillator, the crytsal oscillator unfortunately cannot be used (efficiently/effectively) by the ATTiny85.

The AVR core clock is run from an internal oscillator to generate 8 MHz. The required fuse bytes setting is included in the generated ELF object file in the .fuse section, in the order (low, high, extended). See the source code of MacRTC.c for more information on electrical specifications and the like.

Reference source, Visited 2020-08-05:

Device Programming

Please note: For the ATTiny85 form factor, the external RESET pin must be disabled since it is used for the 1-second interrupt output. Therefore, after the initial programming, it will only be possible to reprogram via high-voltage serial programming.