/**
 * ----------------------------------------------------------------------------
 * This is a MFRC522 library example; see https://github.com/miguelbalboa/rfid
 * for further details and other examples.
 * 
 * NOTE: The library file MFRC522.h has a lot of useful info. Please read it.
 * 
 * Released into the public domain.
 * ----------------------------------------------------------------------------
 * Minimal example how to use the interrupts to read the UID of a MIFARE Classic PICC
 * (= card/tag).
 * 
 * 
 * Typical pin layout used:
 * -----------------------------------------------------------------------------------------
 *             MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
 *             Reader/PCD   Uno/101       Mega      Nano v3    Leonardo/Micro   Pro Micro
 * Signal      Pin          Pin           Pin       Pin        Pin              Pin
 * -----------------------------------------------------------------------------------------
 * RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
 * SPI SS      SDA(SS)      10            53        D10        3                10
 * IRQ         ?            ?             ?         ?          2                10
 * SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
 * SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
 * SPI SCK     SCK          13 / ICSP-3   52        D13        ICSP-3           15
 * 
 */

#include <SPI.h>
#include <MFRC522.h>

constexpr uint8_t RST_PIN = 9;     // Configurable, see typical pin layout above
constexpr uint8_t SS_PIN = 10;     // Configurable, see typical pin layout above
constexpr uint8_t IRQ_PIN = 2;     // Configurable, depends on hardware

MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.

MFRC522::MIFARE_Key key;

volatile boolean bNewInt = false;
byte regVal = 0x7F;
void activateRec(MFRC522 mfrc522);
void clearInt(MFRC522 mfrc522);

/**
 * Initialize.
 */
void setup() {
  Serial.begin(115200); // Initialize serial communications with the PC
  while (!Serial);      // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
  SPI.begin();          // Init SPI bus

  mfrc522.PCD_Init(); // Init MFRC522 card

  /* read and printout the MFRC522 version (valid values 0x91 & 0x92)*/
  Serial.print(F("Ver: 0x"));
  byte readReg = mfrc522.PCD_ReadRegister(mfrc522.VersionReg);
  Serial.println(readReg, HEX);

  /* setup the IRQ pin*/
  pinMode(IRQ_PIN, INPUT_PULLUP);

  /*
   * Allow the ... irq to be propagated to the IRQ pin
   * For test purposes propagate the IdleIrq and loAlert
   */
  regVal = 0xA0; //rx irq
  mfrc522.PCD_WriteRegister(mfrc522.ComIEnReg, regVal);

  bNewInt = false; //interrupt flag

  /*Activate the interrupt*/
  attachInterrupt(digitalPinToInterrupt(IRQ_PIN), readCard, FALLING);

  do { //clear a spourious interrupt at start
    ;
  } while (!bNewInt);
  bNewInt = false;

  Serial.println(F("End setup"));
}

/**
 * Main loop.
 */
void loop() {
  if (bNewInt) { //new read interrupt
    Serial.print(F("Interrupt. "));
    mfrc522.PICC_ReadCardSerial(); //read the tag data
    // Show some details of the PICC (that is: the tag/card)
    Serial.print(F("Card UID:"));
    dump_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
    Serial.println();

    clearInt(mfrc522);
    mfrc522.PICC_HaltA();
    bNewInt = false;
  }

  // The receiving block needs regular retriggering (tell the tag it should transmit??)
  // (mfrc522.PCD_WriteRegister(mfrc522.FIFODataReg,mfrc522.PICC_CMD_REQA);)
  activateRec(mfrc522);
  delay(100);
} //loop()

/**
 * Helper routine to dump a byte array as hex values to Serial.
 */
void dump_byte_array(byte *buffer, byte bufferSize) {
  for (byte i = 0; i < bufferSize; i++) {
    Serial.print(buffer[i] < 0x10 ? " 0" : " ");
    Serial.print(buffer[i], HEX);
  }
}
/**
 * MFRC522 interrupt serving routine
 */
void readCard() {
  bNewInt = true;
}

/*
 * The function sending to the MFRC522 the needed commands to activate the reception
 */
void activateRec(MFRC522 mfrc522) {
  mfrc522.PCD_WriteRegister(mfrc522.FIFODataReg, mfrc522.PICC_CMD_REQA);
  mfrc522.PCD_WriteRegister(mfrc522.CommandReg, mfrc522.PCD_Transceive);
  mfrc522.PCD_WriteRegister(mfrc522.BitFramingReg, 0x87);
}

/*
 * The function to clear the pending interrupt bits after interrupt serving routine
 */
void clearInt(MFRC522 mfrc522) {
  mfrc522.PCD_WriteRegister(mfrc522.ComIrqReg, 0x7F);
}