qmk-firmware/platforms/avr/timer_avr.h

/*
Copyright 2011 Jun Wako <wakojun@gmail.com>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#pragma once

#include <stdint.h>

#ifndef TIMER_PRESCALER
#    if F_CPU > 16000000
#        define TIMER_PRESCALER 256
#    elif F_CPU > 2000000
#        define TIMER_PRESCALER 64
#    elif F_CPU > 250000
#        define TIMER_PRESCALER 8
#    else
#        define TIMER_PRESCALER 1
#    endif
#endif
#define TIMER_RAW_FREQ (F_CPU / TIMER_PRESCALER)
#define TIMER_RAW TCNT0
#define TIMER_RAW_TOP (TIMER_RAW_FREQ / 1000)

#if (TIMER_RAW_TOP > 255)
#    error "Timer0 can't count 1ms at this clock freq. Use larger prescaler."
#endif