64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
#include <io.h>
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#include <interrupt.h>
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#include <signal.h>
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#ifndef OCR1A
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#define OCR1A OCR1 // 2313 support
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#endif
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#ifndef WGM12
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#define WGM12 CTC1 // 2313 support
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#endif
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//#define XTAL 11059201L // nominal value
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#define XTAL 20000000L
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#define DEBOUNCE 256L // debounce clock (256Hz = 4msec)
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#define uint8_t unsigned char
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#define uint unsigned int
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uint8_t prescaler;
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uint8_t volatile second; // count seconds
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SIGNAL (SIG_OUTPUT_COMPARE1A)
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{
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#if XTAL % DEBOUNCE // bei rest
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OCR1A = XTAL / DEBOUNCE - 1; // compare DEBOUNCE - 1 times
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#endif
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if( --prescaler == 0 ){
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prescaler = (uint8_t)DEBOUNCE;
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second++; // exact one second over
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#if XTAL % DEBOUNCE // handle remainder
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OCR1A = XTAL / DEBOUNCE + XTAL % DEBOUNCE - 1; // compare once per second
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#endif
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}
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}
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uint16_t timer_start( void )
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{
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TCCR1B = (1<<WGM12) | (1<<CS10); // divide by 1
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// clear on compare
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OCR1A = XTAL / DEBOUNCE - 1; // Output Compare Register
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TCNT1 = 0; // Timmer startet mit 0
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second = 0;
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prescaler = (uint8_t)DEBOUNCE; //software teiler
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TIMSK = 1<<OCIE1A; // beim Vergleichswertes Compare Match
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// Interrupt (SIG_OUTPUT_COMPARE1A)
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sei();
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}
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uint16_t timer_stop(void)
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{
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cli():
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return second
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}
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