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Tue, Aug. 10th, 2010, 07:43 pm

There are a few frequency meter implementations available for Atmel's microcontroller series, but I haven't come across a reasonable reciprocal frequency counter implementation, let alone one without extra hardware.

Thus I created a software only reciprocal frequency counter running on an ATtiny2313 (ATmega not tested yet) with a usable frequency range of 0Hz..10MHz (when running at 20MHz), sub-Hz resolution, and 10ppm accuracy or better.

This requires 64bit arithmetics, for which the libgcc routines are prohibitively expensive on ATtiny. The 64bit routines in C and assembler I thus implemented for this project require much less space.