// Function prototypes
void setup(void);
void loop(void);

// RDM6300 packet details
#define RDM6300_PACKET_SIZE  14
#define RDM6300_PACKET_BEGIN 0x02
#define RDM6300_PACKET_END   0x03

// Globack for reading RFID data
char buff[RDM6300_PACKET_SIZE];
uint32_t tag_id;
uint8_t checksum;

void setup(void) {
  Serial.begin(9600);
  Serial.println("Setting up...");

  // RFID board setup
  Serial1.begin(9600);

  Serial.println("READY. Scanning tags...");
}

void loop(void) {
  while (Serial1.available() > 0) {
    if (Serial1.peek() == RDM6300_PACKET_BEGIN || Serial1.read()) {
      Serial1.readBytes(buff, RDM6300_PACKET_SIZE);
      if (buff[13] != RDM6300_PACKET_END) {
        Serial.println("Bad1");
      }
      else {
        buff[13] = 0;
        checksum = strtol(buff + 11, NULL, 16);
        buff[11] = 0;
        tag_id = strtol(buff + 3, NULL, 16);
        buff[3] = 0;
        checksum ^= strtol(buff + 1, NULL, 16);
        for (uint8_t i = 0; i < 32; i += 8) checksum ^= ((tag_id >> i) & 0xFF);
        if (checksum) {
          Serial.println("Bad2");
        }
        else {
          Serial.println(tag_id);
        }
      }
    }
    else {
      Serial.println("Bad3");
      Serial.println(Serial1.peek(), HEX);
    }
    Serial.println("END");
  }
}