Lamp Controller based on ATMega328

lamp.c

// 2010 Kenneth Finnegan
// kennethfinnegan.blogspot.com
//
// Control System for 4 channel lamp system
//
// Digital outputs are fed into TRIACs to control 120VAC
//
// Digital inputs come from push buttons and 120VAC light switch

// PC[0..3] - Push buttons
// PD2 - Push buttons
//
// 2010 11 15:	Intial Revision

#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>

#define F_CPU	16000000L
#define NUM_BUTTONS 	5

volatile unsigned char newtick = 0;
volatile unsigned char lightstate = 0;
volatile unsigned char buttondebounce[NUM_BUTTONS];

int main(void) {
	DDRB  = 0x01; // Light output ch4
	PORTB = 0x00;
	DDRC  = 0x00;
	PORTC = 0x0F; // Pullups on buttons
	DDRD  = 0xE0; // Light output ch[1..3]
	PORTD = 0x04; // Pullups on buttons

	// Setup Timer 0
	TCCR0A = 0x00;
	// Use /1024 prescaler
	TCCR0B = (1<<CS02) | (1<<CS00);
	// Enable overflow vector, 64Hz
	TIMSK0 = (1<<TOIE0);

	// Enable pin change int
	PCICR = (1<<PCIE1) | (1<<PCIE0);
	PCMSK0 = 0x02;
	PCMSK1 = 0x0F; // PC[0..3]

	sei();

	char i = 0;

	while(1) {
		if (newtick) { // 64Hz tick
			newtick--;
			char i;
			// decrement debounce timers
			for (i=0; i<NUM_BUTTONS; i++) {
				if (buttondebounce[i])
					buttondebounce[i]--;
			}
			PORTB = (0xFE & PORTB) | ((lightstate>>3) & 1);
			PORTD = (0x1F & PORTD) | ((lightstate<<5));
		}
	}
}

// 64Hz newtick timer
SIGNAL (SIG_OVERFLOW0) {
	newtick++;
}

// Light switch change
SIGNAL (SIG_PIN_CHANGE0) {
	if (PINB & 0x02) { // light switch on
		lightstate |= 0x05;
	} else { // light switch off
		lightstate = 0x00;
	}
}

// Button presses
SIGNAL (SIG_PIN_CHANGE1) {
	char i;
	for (i=0; i<4; i++) {
		if (!(PINC & (1<<i)) && !buttondebounce[i]) {
			lightstate ^= (1<<i);
			buttondebounce[i] = 16;
		}
	}
}