const byte pinRF = 21;  // Pin where RF Module is connected. If necessary, change this for your project

struct rfControl        //Struct for RF Remote Controls
{
   unsigned long addr;  //ADDRESS CODE
   boolean btn1;        //BUTTON 1
   boolean btn2;        //BUTTON 2
};

boolean ACT_HT6P20B_RX(struct rfControl &_rfControl){

  static boolean startbit;      //checks if start bit was identified
  static int counter;           //received bits counter: 22 of Address + 2 of Data + 4 of EndCode (Anti-Code)
  static unsigned long buffer;  //buffer for received data storage

  int lambda;      // on pulse clock width (if fosc = 2KHz than lambda = 500 us)
  int dur0, dur1;  // pulses durations (auxiliary)

  if (!startbit)
  {// Check the PILOT CODE until START BIT;
    dur0 = pulseIn(pinRF, LOW);  //Check how long DOUT was "0" (ZERO) (refers to PILOT CODE)

    //If time at "0" is between 9200 us (23 cycles of 400us) and 13800 us (23 cycles of 600 us).
    if((dur0 > 9200) && (dur0 < 13800) && !startbit)
    {
      //calculate wave length - lambda
      lambda = dur0 / 23;

      //Reset variables
      dur0 = 0;
      buffer = 0;
      counter = 0;

      startbit = true;
    }
  }

  //If Start Bit is OK, then starts measure os how long the signal is level "1" and check is value is into acceptable range.
  if (startbit && counter < 28)
  {
    ++counter;

    dur1 = pulseIn(pinRF, HIGH);

    if((dur1 > 0.5 * lambda) && (dur1 < (1.5 * lambda)))  //If pulse width at "1" is between "0.5 and 1.5 lambda", means that pulse is only one lambda, so the data é "1".
    {
      buffer = (buffer << 1) + 1;   // add "1" on data buffer
    }
    else if((dur1 > 1.5 * lambda) && (dur1 < (2.5 * lambda)))  //If pulse width at "1" is between "1.5 and 2.5 lambda", means that pulse is two lambdas, so the data é "0".
    {
      buffer = (buffer << 1);       // add "0" on data buffer
    }
    else
    {
      //Reset the loop
      startbit = false;
    }
  }

  //Check if all 28 bits were received (22 of Address + 2 of Data + 4 of Anti-Code)
  if (counter==28)
  {
    // Check if Anti-Code is OK (last 4 bits of buffer equal "0101")
    if ((bitRead(buffer, 0) == 1) && (bitRead(buffer, 1) == 0) && (bitRead(buffer, 2) == 1) && (bitRead(buffer, 3) == 0))
    {
      counter = 0;
      startbit = false;

      //Get ADDRESS CODE from Buffer
      _rfControl.addr = buffer >> 6;

      //Get Buttons from Buffer
       _rfControl.btn1 = bitRead(buffer,4);
       _rfControl.btn2 = bitRead(buffer,5);

      //Serial.print("Address: "); Serial.println(_rfControl.addr, HEX);
      //Serial.print("Button1: "); Serial.println(_rfControl.btn1, BIN);
      //Serial.print("Button2: "); Serial.println(_rfControl.btn2, BIN);
      //Serial.println();

      //If a valid data is received, return OK
      return true;
    }
    else
    {
      //Reset the loop
      startbit = false;
    }
  }

  //If none valid data is received, return NULL and FALSE values
  _rfControl.addr = NULL;
  _rfControl.btn1 = NULL;
  _rfControl.btn2 = NULL;

  return false;
}