code: def mpsse_read_gpio(self):
          
          # Send command to read low byte and high byte.
          self._write('\x81\x83')
          # Wait for 2 byte response.
          data = self._poll_read(2)
          # Assemble response into 16 bit value.
          low_byte = ord(data[0])
          high_byte = ord(data[1])
          logger.debug('Read MPSSE GPIO low byte = {0:02X} and high byte = {1:02X}'.format(low_byte, high_byte))
          return (high_byte << 8) | low_byte
docs: Read both GPIO bus states and return a 16 bit value with their state.
          D0-D7 are the lower 8 bits and C0-C7 are the upper 8 bits.