Philips Sonicare NFC Password generation

#include <stdio.h>
#include <stdint.h>
// Philips Sonicare NFC Head Password calculation by @atc1441
uint16_t CRC16(uint16_t crc, uint8_t *buffer, int len) // Default CRC16 Algo
{
  while(len--)
  {
    crc ^= *buffer++ << 8;
    int bits = 0;
    do
    {
      if ( (crc & 0x8000) != 0 )
        crc = (2 * crc) ^ 0x1021;
      else
        crc *= 2;
    }
    while ( ++bits < 8 );
  }
  return crc;
}

uint8_t nfctag_uid[] = {0x04,0xEC,0xFC,0xA2,0x94,0x10,0x90}; // NTAG UID
uint8_t nfc_second[] = "221214 12K"; // Head MFG String, printed on Head and at memory location 0x23

int main()
{
    uint32_t crc_calc = CRC16(0x49A3, nfctag_uid, 7); // Calculate the NTAG UID CRC
    
    crc_calc = crc_calc | (CRC16(crc_calc, nfc_second, 10) << 16); // Calculate the MFG CRC
    
    crc_calc = (crc_calc >> 8) & 0x00FF00FF | (crc_calc << 8) & 0xFF00FF00; // Rotate the uin16_t bytes
    
    printf("by @ATC1441 NFC CRC : 0x%08X expected: 0x61F0A50F\r\n", crc_calc);// Print out the calucated password

    return 0;
}