rc5.c

gehe zur Dokumentation dieser Datei

/*
 * rc5.c Infrarot Fernbedienung Funktionen
 *
 * This program is free software; you can redistribute it
 * and/or modify it under the terms of the GNU General
 * Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your
 * option) any later version.
 * This program is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE. See the GNU General Public License for more details.
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307, USA.
 *
 */

// Infos ueber RC6: http://www.xs4all.nl/~sbp/knowledge/ir/rc6.htm
// http://www.xs4all.nl/~sbp/knowledge/ir/ir.htm

// ========================================================================
// RC5 Infrarot-Empfaenger
// ========================================================================
#include <avr/io.h>
#include "rc5.h"


// -----------------------------------------------------------------------------
// Timing
// -----------------------------------------------------------------------------
#define IR_SAMPLES_PER_BIT     8   
#define IR_SAMPLES_PER_BIT_EARLY 6  
#define IR_SAMPLES_PER_BIT_LATE 10  
#define IR_SAMPLES_PER_BIT_MIN   3  
#define IR_PAUSE_SAMPLES       250  
// Pegelaenderung gueltig -- eigentlich muesste
// man rund 500 Samples abwarten (50 x
// Bitzeit), doch weil der Samplezaehler ein
// Byte ist, beschraenken wir uns hier auf ein
// Minimum von 250 Samples

#define IR_PORT   PORTD     
#define IR_DDR    DDRD      
#define IR_PINR   PIND      
#define IR_PIN    PD0       
static uint8_t     RC5lastsample = 0;  
static uint8_t     RC5bittimer   = 0;  
static uint16_t    RC5data_tmp = 0;    
static uint8_t     RC5bitcount = 0;    
volatile uint16_t  RC5data = 0;        
volatile uint8_t   enableRC5 = 0;      
void IsrRC5 (void)
{
  // sample lesen
  uint8_t sample = 1;

  if ((IR_PINR & (1<<IR_PIN)) != 0)
  {
    sample = 0;
  }

  // bittimer erhoehen (bleibt bei 255 stehen)
  if (RC5bittimer<255)
  {
    RC5bittimer++;
  }

  // flankenerkennung
  if ( RC5lastsample != sample)
  {
    if (RC5bittimer<=IR_SAMPLES_PER_BIT_MIN)
    {
      // flanke kommt zu frueh: paket verwerfen
      RC5bitcount=0;
    }
    else
    {
      // Startbit
      if (RC5bitcount==0)
      {
        if ( (sample==1) && (RC5bittimer>IR_PAUSE_SAMPLES) )
        {
          // Startbit speichern
          RC5data_tmp = 1;
          RC5bitcount++;
        }
        else
        {
          // error
          RC5data_tmp = 0;
        }

        // bittimer-reset
        RC5bittimer = 0;

        // Bits 2..14: nur Flanken innerhalb des Bits beruecksichtigen
      }
      else
      {
        if (RC5bittimer >= IR_SAMPLES_PER_BIT_EARLY)
        {
          if (RC5bittimer<=IR_SAMPLES_PER_BIT_LATE)
          {
            // Bit speichern
            RC5data_tmp = (RC5data_tmp<<1) | sample;
            RC5bitcount++;
          }
          else
          {
            // zu spaet: paket verwerfen
            RC5bitcount = 0;
          }

          // bittimer-reset
          RC5bittimer = 0;
        }
      }
    }

  }
  else
  {
    // keine flanke innerhalb bitzeit?
    if (RC5bittimer > IR_SAMPLES_PER_BIT_LATE)
    {
      // 14 bits gelesen?
      if (RC5bitcount==14)
      {
        RC5data = RC5data_tmp;
      }
      // paket verwerfen
      RC5bitcount = 0;
    }
  }

  // sample im samplepuffer ablegen
  RC5lastsample = sample;


}


uint16_t ReadRC5 (void)
{
  uint16_t retvalue = RC5data;
  RC5data = 0;
  return retvalue;
}

void InitRC5 (void)
{
  IR_DDR  &= ~IR_PIN;   // Pin auf Input
  IR_PORT |= IR_PIN;    // Pullup an
  enableRC5 = 1;
}

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