first re-commit.

pigpio-master/EXAMPLES/CPP/ROTARY_ENCODER/rotary_encoder.cpp

@@ -0,0 +1,84 @@
+#include <iostream>
+
+#include <pigpio.h>
+
+#include "rotary_encoder.hpp"
+
+/*
+
+             +---------+         +---------+      0
+             |         |         |         |
+   A         |         |         |         |
+             |         |         |         |
+   +---------+         +---------+         +----- 1
+
+       +---------+         +---------+            0
+       |         |         |         |
+   B   |         |         |         |
+       |         |         |         |
+   ----+         +---------+         +---------+  1
+
+*/
+
+void re_decoder::_pulse(int gpio, int level, uint32_t tick)
+{
+   if (gpio == mygpioA) levA = level; else levB = level;
+
+   if (gpio != lastGpio) /* debounce */
+   {
+      lastGpio = gpio;
+
+      if ((gpio == mygpioA) && (level == 1))
+      {
+         if (levB) (mycallback)(1);
+      }
+      else if ((gpio == mygpioB) && (level == 1))
+      {
+         if (levA) (mycallback)(-1);
+      }
+   }
+}
+
+void re_decoder::_pulseEx(int gpio, int level, uint32_t tick, void *user)
+{
+   /*
+      Need a static callback to link with C.
+   */
+
+   re_decoder *mySelf = (re_decoder *) user;
+
+   mySelf->_pulse(gpio, level, tick); /* Call the instance callback. */
+}
+
+re_decoder::re_decoder(int gpioA, int gpioB, re_decoderCB_t callback)
+{
+   mygpioA = gpioA;
+   mygpioB = gpioB;
+
+   mycallback = callback;
+
+   levA=0;
+   levB=0;
+
+   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, _pulseEx, this);
+   gpioSetAlertFuncEx(gpioB, _pulseEx, this);
+}
+
+void re_decoder::re_cancel(void)
+{
+   gpioSetAlertFuncEx(mygpioA, 0, this);
+   gpioSetAlertFuncEx(mygpioB, 0, this);
+}
+