#include <avr/io.h>
uint8_t c = 0;
/* Make sure the WDTON Fuse is unprogrammed */
int main() {
DDRB = (1 << PB0) | (1 << PB2) | (1 << PB3);
SPCR = (1 << SPE) | (1 << MSTR);
WDTCR = (1 << WDP2) | (1 << WDP1);
GIMSK = (1 << PCIE);
PCMSK = (1 << PCINT4);
sei();
while(1) {
sleep_cpu();
}
}
uint8_t sent = 0;
ISR(WDT_vect) {
if(sent) {
while(!(SPSR & (1 << SPIF)));
}
SPDR = c;
c = 0;
sent = 1;
}
ISR(PCINT0_vect) {
if(c < -1 && (PORTB & (1 << PB4))) {
c++;
}
}