@staticmethod
def _calculate_checksum(data, number_of_bytes):
    """5.7 CRC Checksum using the polynomial given in the datasheet
		Credits: https://github.com/jaques/sht21_python/blob/master/sht21.py
		"""
    POLYNOMIAL = 305
    crc = 0
    for byteCtr in range(number_of_bytes):
        crc ^= data[byteCtr]
        for bit in range(8, 0, -1):
            if crc & 128:
                crc = crc << 1 ^ POLYNOMIAL
            else:
                crc = crc << 1
    return crc
