rotary_encoder.c

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#include <stdio.h>
#include <stdlib.h>
 
#include <pigpio.h>
 
#include "rotary_encoder.h"
 
struct _Pi_Renc_s
{
   int gpioA;
   int gpioB;
   Pi_Renc_CB_t callback;
   int levA;
   int levB;
   int lastGpio;
};
 
/*
 
             +---------+         +---------+      0
             |         |         |         |
   A         |         |         |         |
             |         |         |         |
   +---------+         +---------+         +----- 1
 
       +---------+         +---------+            0
       |         |         |         |
   B   |         |         |         |
       |         |         |         |
   ----+         +---------+         +---------+  1
 
*/
 
static void _cb(int gpio, int level, uint32_t tick, void *user)
{
   Pi_Renc_t *renc;
 
   renc = user;
 
   if (gpio == renc->gpioA) renc->levA = level; else renc->levB = level;
 
   if (gpio != renc->lastGpio) /* debounce */
   {
      renc->lastGpio = gpio;
 
      if ((gpio == renc->gpioA) && (level == 1))
      {
         if (renc->levB) (renc->callback)(1);
      }
      else if ((gpio == renc->gpioB) && (level == 1))
      {
         if (renc->levA) (renc->callback)(-1);
      }
   }
}
 
Pi_Renc_t * Pi_Renc(int gpioA, int gpioB, Pi_Renc_CB_t callback)
{
   Pi_Renc_t *renc;
 
   renc = malloc(sizeof(Pi_Renc_t));
 
   renc->gpioA = gpioA;
   renc->gpioB = gpioB;
   renc->callback = callback;
   renc->levA=0;
   renc->levB=0;
   renc->lastGpio = -1;
 
   gpioSetMode(gpioA, PI_INPUT);
   gpioSetMode(gpioB, PI_INPUT);
 
   /* pull up is needed as encoder common is grounded */
 
   gpioSetPullUpDown(gpioA, PI_PUD_UP);
   gpioSetPullUpDown(gpioB, PI_PUD_UP);
 
   /* monitor encoder level changes */
 
   gpioSetAlertFuncEx(gpioA, _cb, renc);
   gpioSetAlertFuncEx(gpioB, _cb, renc);
}
 
void Pi_Renc_cancel(Pi_Renc_t *renc)
{
   if (renc)
   {
      gpioSetAlertFunc(renc->gpioA, 0);
      gpioSetAlertFunc(renc->gpioB, 0);
 
      free(renc);
   }
}