AM digital transmission + wiringPi

digital_transmit.cpp

// This uses those super cheap 433mhz modules to receive a 32 bit integer
// You should be able to implement many 315 & 433mhz protocols in this, though more complex lock logic may be required

#include <wiringPi.h>
#include <time.h>
#include <iostream>
#include <bitset>

using namespace std;

#define MAX_CHANGE_TO_KEEP 32
#define LOW_PULSE 350 // microseconds
#define HIGH_PULSE 1100 // microseconds
#define LOCK 11200
#define TOLERANCE 150 // LOW/HIGH +/- TOLERANCE, LOCK +/- TOLERANCE*10

static bitset<32> bits; // The bits we care about
static bitset<32> checkBits; // The previous value, as a sanity check

void handleInterrupt() {
 
  static unsigned int duration;
  static unsigned int changeCount;
  static unsigned long lastTime;

  static int lockPassed;

  long time = micros();
  duration = time - lastTime;


  //wait for lock
  if (duration > LOCK - (TOLERANCE*10) && duration < LOCK + (TOLERANCE*10) && lockPassed == 0) { 
    changeCount = 0;
    lockPassed = 1;

    bits.reset();
  } 
  else if (lockPassed != 0) { // REST OF DATA

    // We're done! Print the packet
    if (changeCount >= MAX_CHANGE_TO_KEEP || duration > 2000) { 

      if (changeCount >= MAX_CHANGE_TO_KEEP) {

        if (checkBits == bits) {
          cout << bits.to_ulong() << '\n';
        }

        // Copy to sanity check bitset
        for (unsigned int i = 0; i < MAX_CHANGE_TO_KEEP; i++) {
          checkBits[i] = bits[i];
        }

      }

      lockPassed = 0;

    // Otherwise, store the bit  
    } else {
      if ((duration > LOW_PULSE - TOLERANCE && duration < LOW_PULSE + TOLERANCE) || (duration > HIGH_PULSE - TOLERANCE && duration < HIGH_PULSE + TOLERANCE) ) {
        // HIGH
        if (digitalRead(1) == 0 && (duration > HIGH_PULSE - TOLERANCE && duration < HIGH_PULSE + TOLERANCE)) {
          bits.set(MAX_CHANGE_TO_KEEP - changeCount++ - 1, true);
        }
        // LOW
        if (digitalRead(1) == 0 && (duration > LOW_PULSE - TOLERANCE && duration < LOW_PULSE + TOLERANCE)) {
          bits.set(MAX_CHANGE_TO_KEEP - changeCount++ - 1, false);
        }
      }
    }
  }

  lastTime = time;  
}



int main(void) {
  if(wiringPiSetup() == -1)
       return 0;

  //attach interrupt to changes on the pin
  if ( wiringPiISR (1, INT_EDGE_BOTH, &handleInterrupt) < 0 ) {
      return 1;
  }
  //interrupt will handle changes
  while(true);
}