#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/pgmspace.h>

#define ENCODER_PIN PIND
#define PHASE_A     (1<<PD1)
#define PHASE_B     (1<<PD0)

#define CHARLIE_CNT  3		// max number of active LEDs 

volatile int8_t enc_delta;          // -128 ... 127
volatile uint8_t flag_100ms;
volatile uint16_t leds[CHARLIE_CNT];			// MUX data for charliplexing
const uint16_t led_codes[16] PROGMEM = {
	// high byte -> DDRx, low byte -> PORTx
 	0x6040,		// LED1
	0x6020,		// LED2
	0x5040,		// LED3
	0x5010,		// LED4
	0x4840,		// LED5
	0x4808,		// LED6
	0x4440,		// LED7
	0x4404,		// LED8
	0x3020,		// LED9
	0x3010,		// LED10
	0x2820,		// LED11
	0x2808,		// LED12
	0x2420,		// LED13
	0x2404,		// LED14
	0x1810,		// LED15
	0x1808		// LED16
};

uint8_t richtung;
int8_t led_state;

// read 1, 2, or 4 step encoders
int8_t encode_read( uint8_t step )    { 
  int8_t val;

  // atomic access to enc_delta
  cli();
  val = enc_delta;
  switch (step) {
    case  2: enc_delta = val & 1; val >>= 1; break;
    case  4: enc_delta = val & 3; val >>= 2; break;
    default: enc_delta = 0; break;
  }
  sei();
  return val;                   // counts since last call
}

void led_refresh(void) {

	int i, j;

	// LED Band rotieren
		
	if (richtung) {	// rechts rotieren
		led_state++;
		if (led_state > 14) led_state = 0;
	} else {	// links rotieren
		led_state--;
		if (led_state < 0) led_state = 14;
	}

	j = led_state;

	// Charliplexing aktualisieren
	for (i=0; i<CHARLIE_CNT; i++) {
		leds[i] = pgm_read_byte(&led_codes[j]);
		j++;
		if (j > 14) j = 0;
	}

}


int main(void) {
	
	int8_t tmp;

	// init IOs

	DDRD = (1<<PD6) | (1<<PD5) | (1<<PD4) | (1<<PD3) | (1<<PD2);	// outputs for LEDs, charliplexing
	PORTD = (1<<PD1) | (1<<PD0);		// internal pull ups for encoder inputs

	// init timer 0, mode 0, prescaler 64
	// F_TIMER = F_CPU / 64 / 256 = 8 MHz / 64 / 256 = 488Hz
	TCCR0A = 0;
	TCCR0B = (1<CS02);	
	TIMSK |= (1<<TOIE0);

	sei();
	
	while(1) {
		set_sleep_mode(SLEEP_MODE_IDLE);
		sleep_mode();
		if(flag_100ms) {
			flag_100ms = 0;
			tmp = encode_read(4);
			if (tmp > 0) richtung = 1;
			if (tmp < 0) richtung = 0;			
			led_refresh();
		}
	}		
}

// timer 0 overflow ISR, 488Hz

ISR(TIMER0_OVF_vect) {

	int8_t new, diff, tmp;
  	static int8_t last, cnt, cnt_led;
	uint16_t tmp1;

	// decode rotary encoder

  	tmp = ENCODER_PIN;
  	new = 0;
  	if ( tmp & PHASE_A ) new  = 3;
  	if ( tmp & PHASE_B ) new ^= 1;   // convert gray to binary
  	diff = last - new;               // difference last - new
  	if( diff & 1 ) {                 // bit 0 = value (1)
    	last = new;                    // store new as next last
    	enc_delta += (diff & 2) - 1;   // bit 1 = direction (+/-)
  	}

	// 10ms flag counter

	cnt++;
	if (cnt == 48) {
		cnt = 0;
		flag_100ms = 1;
	}

	// charlieplexing

	PORTD = 0x3;		// all LEDs off, only pull ups active
	cnt_led++;
	if (cnt_led == CHARLIE_CNT) cnt_led = 0;
	tmp1  = leds[cnt_led];
	DDRD  = tmp1>>8;	// new led code
	PORTD = tmp1 | 0x3;
		
}