I need to recognize a signal from an IR remote, not to use a library for working with IR remotes/receivers. How can when the button is clicked to display its name. I have PIC12F615 microcontroller with this code: code and 5 buttons connected to him and I need recognise which button pressed. Why NEC IR remote control decoder does not work, pulseLengthLastUs is always false in this condition: pulseLengthLastUs > 8000 && pulseLengthLastUs < 10000 on any button press.

volatile boolean nec_ok = 0;
byte command, inv_command;
volatile byte nec_state = 0 ;
unsigned int address;
volatile unsigned long nec_code;
volatile uint32_t errFlag = 0 ;
volatile uint32_t decodeStartAtMs = 0 ;


void setup() {
  Serial.begin(9600);
  pinMode( 2, INPUT_PULLUP ) ;
  attachInterrupt(digitalPinToInterrupt(2), remote_read, CHANGE); // Enable external interrupt (INT0)
}

void remote_read() {

  static byte i = 0 ;
  static bool wasSpace;
  static unsigned long enteredAtUs = 0 ;
  static unsigned long pulseLengthLastUs ;

  wasSpace = ! digitalRead( 2 ) ;
  pulseLengthLastUs = micros() - enteredAtUs; // Calculate pulse length
  enteredAtUs = micros(); // Store current time for next entry


  switch (nec_state) {

    case 0 : // Wait here until 9ms pulse found )
      if ( pulseLengthLastUs > 8000 && pulseLengthLastUs < 10000 ) {  // got a 9ms pulse
        decodeStartAtMs = millis() ;  // for timeout
        nec_state = 1 ;
        nec_code = 0 ;
        i = 0 ;
      }
      break;

    case 1 : // handle 4.5ms space
      if ((pulseLengthLastUs > 5500) || (pulseLengthLastUs < 3500)) {
        errFlag = 10000000 + pulseLengthLastUs ;
        nec_state = 0; // Reset decoding process
      }
      else
        nec_state = 2; // Next state: end of 562µs pulse (start of 562µs or 1687µs space)
      break;


    case 2 : // handle 562µs or 1687µs space
      if ((pulseLengthLastUs > 1900) || (pulseLengthLastUs < 400)) { // Time interval invalid ==> stop decoding
        errFlag = 20000000 + pulseLengthLastUs ;
        nec_state = 0; // Reset decoding process
        break;
      }

      if ( wasSpace ) {
        // we are interested only in the space length
        if ( pulseLengthLastUs > 1000) // If space width > 1ms (short space)
          bitSet(nec_code, (31 - i)); // Write 1 to bit (31 - i)
        else // If space width < 1ms (long space)
          bitClear(nec_code, (31 - i)); // Write 0 to bit (31 - i)
        i++;
        if (i > 31) { // If all bits are received
          i = 0 ;
          nec_ok = 1; // Decoding process OK
          detachInterrupt(0); // Disable external interrupt (INT0)
        }
      }
      break;
  }
}

void loop() {

  if ( errFlag > 0 ) {
    Serial.print( "Error: " ) ;
    Serial.println( errFlag ) ;
    errFlag = 0 ;
  }

  if ( nec_state > 0 && millis() - decodeStartAtMs > 90 ) {
    Serial.println( "Timeout" ) ;
    nec_state = 0 ;
  }


  if (nec_ok) {
    Serial.print( "Code received = " ) ;
    Serial.println( nec_code, HEX ) ;

    address = (nec_code >> 16) & 0xFF; // Extract address from received code
    inv_command = (nec_code >> 8) & 0xFF; // Extract inverted command from received code
    command = nec_code & 0xFF; // Extract command from received code
    if (command == ((~inv_command) & 0xFF)) { // Verify command validity
      Serial.print("Received valid NEC code: ");
      Serial.print(address, HEX); Serial.print(", ");
      Serial.print(command, HEX); Serial.print(", ");
      Serial.println(inv_command, HEX);
    }
    else {
      Serial.println("Received invalid NEC code!");
    }
    nec_ok = 0; // Reset decoding process
    nec_state = 0; // Reset decoding state
    attachInterrupt(digitalPinToInterrupt(2), remote_read, CHANGE); // Re-enable external interrupt (INT0)
  }

}

Schema in Proteus:

 

Why don't you want to use a library to read and decode the signals from the remote? Have you run the Arduino "check ir" program to see what the protocol of your remote is and what codes correspond to the buttons you want to use? It is also a good example of how to read the remote signal.
I suggest you read this tutorial:
https://roboticsbackend.com/arduino-ir-remote-controller-tutorial-setup-and-map-buttons/

 

Do you know anything about the NEC protocol? Also I did not see an IR sensor in your diagram. Did I miss something?