// bike odometer with binary display
// written by Matt Ball, July 2009, for attiny2313
// thanks to theusch on avrfreaks.net for external clock-counter idea

// todo:
// sleep routine

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

int tenths = 0;
int ones = 0;
int tens = 0;


void init_tc0(void)
{
	TCCR0B = 0x07;              // external rising-edge clock source on T0 pin (the hall sensor)
				    // TCNT0 stores the number of revs; note falling-edge may also be initialized (reed switch)
	TCCR0A = 0x02;              // CTC-mode
	TIMSK |= (1 << OCIE0A);     // enable interrupt on compare match
	sei();                      // enable global interrupts
	OCR0A = 46;		    // 458 revs in one km for my bike; compare match will (roughly) count tenths of a km
}


int main(void) 
{
	int button_tenths = (PINB & 0x04);     // the display switches
	int button_ones   = (PINB & 0x05);
	int button_tens   = (PINB & 0x06);
	
	DDRB = 0b00001111;  		// leds on PB0:3
	
	init_tc0();    			// initialize timer/counter0
	
	if (button_tenths == 0)
	{
		PORTB = tenths;
		_delay_ms(1);
		PORTB = 0;
		_delay_ms(9);    // display at 10% duty cycle
	}
	
	if (button_ones == 0)
	{
		PORTB = ones;
		_delay_ms(1);
		PORTB = 0;
		_delay_ms(9);
	}
	
	if (button_tens == 0)
	{
		PORTB = tens;
		_delay_ms(1);
		PORTB = 0;
		_delay_ms(9);
	}
	
	return 0;
}


ISR(TIMER0_COMPA_vect)    // triggers every tenth of a km
{
	tenths++;
	if (tenths >= 10)
	{
		ones++;
		tenths = 0;
		if (ones >= 10)
		{
			tens++;
			ones = 0;
		}
	}
}