def read_mac(self):
        """ Read MAC from EFUSE region """
        words = [self.read_efuse(2), self.read_efuse(1)]
        bitstring = struct.pack(">II", *words)
        bitstring = bitstring[2:8]  # trim the 2 byte CRC
        try:
            return tuple(ord(b) for b in bitstring)
        except TypeError:  # Python 3, bitstring elements are already bytes
            return tuple(bitstring)