/************************************************************************                                                                   

                      Reading rotary encoder                          
                      one, two and four step encoders supported       
                                                                      
                      Author: Peter Dannegger 
					                                  
                      target: ATmega168  
					  modifiziert Richard S.                                     


************************************************************************/


#define 	F_CPU 8000000UL

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

#include "HD44780.c"

#define XTAL        8e6         // 8MHz

#define ENCODER_PIN PINC
#define PHASE_A     (1<<PC1)
#define PHASE_B     (1<<PC3)

 //  #define LEDS_DDR    DDRB
 //  #define LEDS        PORTB           // LEDs against VCC

volatile int8_t enc_delta;          // -128 ... 127
static int8_t last;
char str1[20];

void encode_init( void ) {
	int8_t new, tmp;

	// init encoder
	
	tmp = ENCODER_PIN;
	new = 0;
	if( tmp & PHASE_A ) new  = 3;
	if( tmp & PHASE_B ) new ^= 1;       // convert gray to binary
	last = new;                         // power on state
	enc_delta = 0;

	// init timer 0
	
	TCCR0B = (0<<CS02) | (1<<CS01) | (1<<CS00);   // CTC, prescaler 64
	TCCR0A = (1<<WGM01);                                                             
	TIMSK0 |= 1<<OCIE0A;
}

ISR( TIMER0_COMPA_vect ) {           // 1ms for manual movement
	int8_t new, diff, tmp;

	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 (+/-)
	}
}

// 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
}

int main( void ) {
	int32_t val = 0;	
	
	LCD_Initialize();

    LCD_GoTo(0,0);               // LCD Ausgabe in 1-te Zeile
    LCD_WriteText("Encoder-Impuls :");
				
	PORTC |= PHASE_A | PHASE_B;       // activate internal pull up resistors	
	
//                  	LEDS_DDR = 0xFF;
     encode_init();
 	sei();
	for(;;){	
		val += encode_read(4);          // read a single step encoder					
   dtostrf(val,4,0,str1);
				
		LCD_GoTo(4,1);               // Go to Second Line
		LCD_WriteText(str1);		
		
//     	                	LEDS = val;

	}
}