#include <avr/common.h>
#define F_CPU 4000000UL
#include <util/delay.h>
#include <avr/interrupt.h>
void setColumnToZero(char bit)
{
bit = 3 - bit;
PORTA &= ~_BV(bit);
}
void setColumnToOne(char bit)
{
bit = 3 - bit;
PORTA |= _BV(bit);
}
char isRowZero(char bit)
{
bit += 4;
return (PINA & _BV(bit)) == _BV(bit);
}
void timer1_init()
{
TCCR1B |= (1 << WGM12)|(1 << CS11)|(1 << CS10);
TCNT1 = 0;
OCR1A = 24;
TIMSK |= (1 << OCIE1A);
sei();
}
ISR (TIMER1_COMPA_vect)
{
for (char i = 0; i < 4; i++)
{
setColumnToZero(i);
for (char j = 0; j < 4; j++)
{
if (isRowZero(j))
{
PORTC = ~_BV(j);
_delay_ms(1000);
PORTC = 0xff;
}
}
setColumnToOne(i);
}
}
void setup()
{
DDRC = 0xff; // input
timer1_init();
}
int main(void)
{
setup();
while(1)
{
}
}
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