first re-commit.

pigpio-master/EXAMPLES/C/IR_RECEIVER/README

@@ -0,0 +1,3 @@
+Function to hash a code from an IR receiver (reading an IR remote control). 
+
+Follow the instructions in the test file to build and run.

pigpio-master/EXAMPLES/C/IR_RECEIVER/ir_hasher.c

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+#include <stdlib.h>
+
+#include <pigpio.h>
+
+#include "ir_hasher.h"
+
+/*
+This code forms a hash over the IR pulses generated by an
+IR remote.
+
+The remote key press is not converted into a code in the manner of
+the lirc module.  No attempt is made to decode the type of protocol
+used by the remote.  The hash is likely to be unique for different
+keys and different remotes but this is not guaranteed.
+
+This hashing process works for some remotes/protocols but not for
+others.  The only way to find out if it works for one or more of
+your remotes is to try it and see.
+*/
+
+struct _Pi_Hasher_s
+{
+   int gpio;
+   Pi_Hasher_CB_t callback;
+   int timeout;
+   int in_code;
+   uint32_t hash_val;
+   int edges;
+   int t1;
+   int t2;
+   int t3;
+   int t4;
+};
+
+
+static uint32_t _hash(uint32_t hv, int old_val, int new_val)
+{
+   int val;
+
+   if      (new_val < (old_val * 0.60)) val = 13;
+   else if (old_val < (new_val * 0.60)) val = 23;
+   else                                 val = 2;
+
+   hv ^= val;
+   hv *= 16777619; /* FNV_PRIME_32 */
+
+   return hv;
+}
+
+static void _cb(int gpio, int level, uint32_t tick, void *user)
+{
+   Pi_Hasher_t * hasher;
+
+   hasher = user;
+
+   if (level != PI_TIMEOUT)
+   {
+      if (hasher->in_code == 0)
+      {
+         hasher->in_code = 1;
+
+         gpioSetWatchdog(gpio, hasher->timeout);
+
+         hasher->hash_val = 2166136261U; /* FNV_BASIS_32 */
+
+         hasher->edges = 1;
+
+         hasher->t1 = 0;
+         hasher->t2 = 0;
+         hasher->t3 = 0;
+         hasher->t4 = tick;
+      }
+      else
+      {
+         hasher->edges++;
+
+         hasher->t1 = hasher->t2;
+         hasher->t2 = hasher->t3;
+         hasher->t3 = hasher->t4;
+         hasher->t4 = tick;
+
+         if (hasher->edges > 3)
+         {
+            hasher->hash_val =
+               _hash(hasher->hash_val,
+                     (hasher->t2)-(hasher->t1),
+                     (hasher->t4)-(hasher->t3));
+         }
+      }
+   }
+   else
+   {
+      if (hasher->in_code)
+      {
+         hasher->in_code = 0;
+
+         gpioSetWatchdog(gpio, 0);
+
+         if (hasher->edges > 12) /* Anything less is probably noise. */
+         {
+            (hasher->callback)(hasher->hash_val);
+         }
+      }
+   }
+}
+
+Pi_Hasher_t *Pi_Hasher(int gpio, Pi_Hasher_CB_t callback, int timeout)
+{
+   Pi_Hasher_t *hasher;
+
+   hasher = malloc(sizeof(Pi_Hasher_t));
+
+   hasher->gpio     = gpio;
+   hasher->callback = callback;
+   hasher->timeout  = 5;
+
+   hasher->in_code = 0;
+
+   gpioSetMode(gpio, PI_INPUT);
+   gpioSetAlertFuncEx(gpio, _cb, hasher);
+
+   return hasher;
+}
+
+void Pi_Hasher_cancel(Pi_Hasher_t *hasher)
+{
+   if (hasher)
+   {
+      gpioSetAlertFunc(hasher->gpio, 0);
+
+      free(hasher);
+
+      hasher = NULL;
+   }
+}
+

pigpio-master/EXAMPLES/C/IR_RECEIVER/ir_hasher.h

@@ -0,0 +1,33 @@
+#ifndef IR_HASHER_H
+#define IR_HASHER_H
+
+#include <stdint.h>
+
+typedef void (*Pi_Hasher_CB_t)(uint32_t);
+
+struct _Pi_Hasher_s;
+
+typedef struct _Pi_Hasher_s Pi_Hasher_t;
+
+Pi_Hasher_t * Pi_Hasher(int gpio, Pi_Hasher_CB_t callback, int timeout);
+   /*
+      This function establishes an IR hasher on the gpio.
+
+      A gap of timeout milliseconds without a new bit indicates
+      the end of a code.
+
+      When code end is detected the callback function is called
+      with the code hash.
+
+      A pointer to a private data type is returned.  This should be passed
+      to Pi_Hasher_cancel if the hasher is to be cancelled.
+   */
+
+
+void Pi_Hasher_cancel(Pi_Hasher_t *hasher);
+   /*
+      This function releases the resources used by the hasher.
+   */
+
+
+#endif

pigpio-master/EXAMPLES/C/IR_RECEIVER/test_ir_hasher.c

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+#include <stdio.h>
+
+#include <pigpio.h>
+
+#include "ir_hasher.h"
+
+/*
+
+REQUIRES
+
+An IR receiver output pin connected to a Pi gpio.
+
+TO BUILD
+
+gcc -o ir_hash_c test_ir_hasher.c  ir_hasher.c -lpigpio -lrt -lpthread
+
+TO RUN
+
+sudo ./ir_hash_c
+
+*/
+
+void callback(uint32_t hash)
+{
+   printf("hash=%u\n", hash);
+}
+
+int main(int argc, char *argv[])
+{
+   Pi_Hasher_t *hasher;
+
+   if (gpioInitialise() < 0) return 1;
+
+   /* 
+      This assumes the output pin of an IR receiver is
+      connected to gpio 7.
+   */
+
+   hasher = Pi_Hasher(7, callback, 5);
+
+   sleep(300);
+
+   Pi_Hasher_cancel(hasher);
+
+   gpioTerminate();
+}
+