rotary.c

/************************************************************************/
/*                                                                      */
/*                      Reading rotary encoder						    */
/*                      one, two and four step encoders supported		*/
/*                                                                      */
/*              Author: Peter Dannegger                                 */
/*                                                                      */
/************************************************************************/
#include <avr/io.h>
//#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include "rotary.h"
 
volatile int8_t enc_delta;          // -128 ... 127
static int8_t last;
 
void encode_init( void )
{
  int8_t new;
 
  new = 0;
  if( PHASE_A )
    new = 3;
  if( PHASE_B )
    new ^= 1;                   // convert gray to binary
  last = new;                   // power on state
  enc_delta = 0;
  TCCR0 = 1<<WGM01^1<<CS01^1<<CS00;     // CTC, XTAL / 64
  OCR0 = (uint8_t)(XTAL / 64.0 * 1e-3 - 0.5);   // 1ms
  TIMSK |= 1<<OCIE0;
}
 
 
 
ISR( TIMER0_COMP_vect )             // 1ms for manual movement
{
  int8_t new, diff;
 
  new = 0;
  if( PHASE_A )
    new = 3;
  if( 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 (+/-)
  }
}
 
 
int8_t encode_read1( void )         // read single step encoders
{
  int8_t val;
 
  cli();
  val = enc_delta;
  enc_delta = 0;
  sei();
  return val;                   // counts since last call
}
 
 
int8_t encode_read2( void )         // read two step encoders
{
  int8_t val;
 
  cli();
  val = enc_delta;
  enc_delta = val & 1;
  sei();
  return val >> 1;
}
 
 
int8_t encode_read4( void )         // read four step encoders
{
  int8_t val;
 
  cli();
  val = enc_delta;
  enc_delta = val & 3;
  sei();
  return val >> 2;
}