Read the ambient light sensor and return it as an unsigned 16-bit value.

def read_ambient(self, timeout_sec=1):
        """Read the ambient light sensor and return it as an unsigned 16-bit value.
        """
        # Ask for an ambient measurement and wait for the response.
        self._device.write8(VCNL40xx_COMMAND, VCNL40xx_MEASUREAMBIENT)
        self._wait_response(VCNL40xx_AMBIENTREADY, timeout_sec)
        # Return the ambient response.
        return self._device.readU16BE(VCNL40xx_AMBIENTDATA)