smbus.py 文件源码

def read_word_data(self, addr, cmd):
        """Read a word (2 bytes) from the specified cmd register of the device.
        Note that this will interpret data using the endianness of the processor
        running Python (typically little endian)!
        """
        assert self._device is not None, 'Bus must be opened before operations are made against it!'
        # Build ctypes values to marshall between ioctl and Python.
        reg = c_uint8(cmd)
        result = c_uint16()
        # Build ioctl request.
        request = make_i2c_rdwr_data([
            (addr, 0, 1, pointer(reg)),             # Write cmd register.
            (addr, I2C_M_RD, 2, cast(pointer(result), POINTER(c_uint8)))   # Read word (2 bytes).
        ])
        # Make ioctl call and return result data.
        ioctl(self._device.fileno(), I2C_RDWR, request)
        return result.value