ftdi_serial.py

import ctypes

__all__ = ['FtdiSerial', 'FtdiException', 'FtdiTimeoutException']

libftdi = ctypes.CDLL('libftd2xx.so')

FT_OK = 0


class FtdiException(Exception):
    pass


class FtdiTimeoutException(Exception):
    pass


class FtdiSerial(object):

    def __init__(self, deviceNumber, speed):
        self._timeout = 30
        rv = libftdi.FT_SetVIDPID(ctypes.c_uint(0x0403), ctypes.c_uint(0x6001))
        self._handle = ctypes.c_void_p()

        rv = libftdi.FT_Open(ctypes.c_int(deviceNumber), ctypes.byref(self._handle))
        if rv != FT_OK:
            raise FtdiException('FT_Open returned %d' % rv)

        rv = libftdi.FT_SetBaudRate(self._handle, speed)
        if rv != FT_OK:
            raise FtdiException('FT_SetBaudRate returned %d' % rv)


    def __del__(self):
        libftdi.FT_Close(self._handle)


    @property
    def timeout(self):
        return self._timeout


    @timeout.setter
    def timeout(self, value):
        self._timeout = value
        rv = libftdi.FT_SetTimeouts(self._handle, ctypes.c_int(int(value*1000)), ctypes.c_int(int(value*1000)))
        if rv != FT_OK:
            raise FtdiException('FT_SetTimeouts returned %d' % rv)


    def read(self, size):
        buffer = b' ' * size
        dwBytesRead = ctypes.c_uint(0)

        rv = libftdi.FT_Read(self._handle, buffer, size, ctypes.byref(dwBytesRead))
        if rv != FT_OK:
            raise FtdiException('FT_Read returned %d' % rv)

        if dwBytesRead.value != size:
            raise FtdiTimeoutException()

        return buffer

    def write(self, data):
        dwBytesWritten = ctypes.c_uint(0)

        buf_size = len(data)
        rv = libftdi.FT_Write(self._handle, data, buf_size, ctypes.byref(dwBytesWritten))
        if rv != FT_OK:
            raise FtdiException('FT_Write returned %d' % rv)

        while dwBytesWritten.value != buf_size:
           # untested :)

            data = data[dwBytesWritten.value:]
            buf_size = len(data)

            if buf_size == 0:
                # done
                break

            rv = libftdi.FT_Write(self._handle, data, buf_size, ctypes.byref(dwBytesWritten))
            if rv != FT_OK:
                raise FtdiException('FT_Write returned %d' % rv)