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#include <avr/interrupt.h>
#include <avr/io.h>
volatile unsigned short adc_value = 0x5555;
volatile unsigned char isr_count = 0;
volatile unsigned int in_loop = 0;
#if defined(PROC_at90s4433) || defined(PROC_atmega8)
#define CTLREG ADCSR
#else
#define CTLREG ADCSRA
#endif
void init(void) {
#ifdef PROC_attiny25
// ADMUX: channel 0, REF=5 (1 would also be possible!)
ADMUX = 0x50;
#else
// ADMUX: channel 0, ADCBG = 0 (at90s4433 only)
ADMUX = 0x00;
#endif
// ADEN = 1, ADFR = 1, ADIE = 1, ADPS = 5 CKx32 = 125kHz
CTLREG = 0xad;
}
ISR(ADC_vect) {
// read ADC value
adc_value = ADCL | (ADCH << 8);
// increment counter
isr_count++;
}
int main(void) {
init();
// start ADC
CTLREG = 0xed;
// enable interrupts
sei();
do {
in_loop = 1;
} while(1); // do forever
}
// EOF
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