Capture/Record IR remote signals with an Arduino

ir_capture.ino

//------------------------------------------------------------------------------

//  Interrupt 0 fires on pin D2
#define IR_PIN 2

//  the maximum pulse we'll listen for
#define MAX_PULSE 30000

// the largest message we expect to receive (in bits)
#define MAX_MSG_SIZE 50

//  These variables hold the info for the incoming IR message.  If we have received
//  a message, then these will hold the message length and the pulse width values.
//  We'll store up to 50 pulse pairs (high and low), which is more than enough. 
volatile uint8_t ir_msg_len = 0;
volatile uint16_t ir_msg[MAX_MSG_SIZE*2]; // pair is high and low pulse


//------------------------------------------------------------------------------
//  Initialize the arduino, attach the interrupt that will fire whenever pin 2 
//  goes HIGH.  (On the Uno, interrupt 0 goes to pin D2, but it depends on the
//  model 

void setup() {
  Serial.begin(9600);
  attachInterrupt( 0, captureIR, RISING );  
  Serial.println("Ready to capture message");
}


//------------------------------------------------------------------------------
//  Test if there is a message (if ir_msg_len > 0) and, if so, print it.

void loop() {
  if (ir_msg_len > 0) {
    // print the message
    Serial.println("message caught:");
    print_message();
    
    // reset to 'no message' state when finished.
    ir_msg_len = 0;
  }
}

//------------------------------------------------------------------------------
//  captureIR() captures the pulse-width data that is delivered to pin 2 when
//  an infrared message triggers the IR sensor.   

uint32_t last_time = 0;
const float cycle_time = (1.0/36000.0)*1000000;   // 27.7778 uS per cycle

void captureIR() {
  
  // If the previous call came in less than 0.25 seconds ago, just ignore it.
  uint32_t now = micros();
  if (now - last_time < 250000)
    return;
  last_time = now;


  // Track the pin as it rises and falls and record the time it spends in HIGH
  // then LOW state.  If we pass MAX_PULSE uS, the message is over.
  uint32_t hightime, lowtime;
  ir_msg_len = 0;
  
  while (ir_msg_len < MAX_MSG_SIZE*2) {
    hightime = pulseIn(IR_PIN, HIGH, MAX_PULSE);
    lowtime = pulseIn(IR_PIN, LOW, MAX_PULSE);
    if ( (hightime == 0) || (lowtime == 0) ) {
        // Finished with message
        return;
    }

    ir_msg[ir_msg_len++] = round(hightime/cycle_time);
    ir_msg[ir_msg_len++] = round(lowtime/cycle_time);
  }
}


//------------------------------------------------------------------------------
// Output the message as a set of pairs in a format that will be easy to cut and
// paste into code in the next step, like this:
//     uint16_t target_seq[5*2] = { 14,15,  62,15,  14,15,  15,15,  900,14 };

void print_message(void) {
  Serial.print("uint16_t target_seq[");
  Serial.print( int(ir_msg_len/2) );
  Serial.print("*2] = { ");
  for (uint8_t i = 0; i < ir_msg_len; i+=2) {
    Serial.print( ir_msg[i] );
    Serial.print(",");
    Serial.print( ir_msg[i+1] );

    if (i != ir_msg_len-2) {
      Serial.print(",  ");
    }
  }
  Serial.println(" };");
}