[Tutor] Serial communication ...

[Markus Hubig]

Hi @all!

I'm about to write a class for serial communication on Win32 and Linux which
provides a method called "talk" to send something over the serial line,
wait for
the answer and returns it. My problem is, that I don't know how long the
answer
will be (ok max 260 bytes but most answers are much smaller).

This is what I have now, please leave some comments:

   1. Will this work on Win32 (with select)?
   2. Should I better use twisted.internet.serialport?
   3. Will self.read(260)block until it reads the full 260 bytes?

class SerialDevice(Serial):

    def __init__(self,port):
        Serial.__init__(self)
        self.port = port
        self.baudrate = 57600
        self.bytesize = EIGHTBITS
        self.parity = PARITY_ODD
        self.stopbits = STOPBITS_TWO
        self.timeout = 0
        self.xonxoff = 0
        self.rtscts = 0
        self.dsrdtr = 0
        self.open()
        self.flush()

    def _write(self, packet):
        fileno = self.fileno()
        while True:
            readable, writeable, excepts = select( [], [fileno], [], 0.2 )
            if fileno in writeable:
                time.sleep(0.1)
                length = self.write(packet)
                break
        return length

    def _read(self):
        fileno = self.fileno()
        while True:
            readable, writeable, excepts = select( [], [fileno], [], 0.2 )
            if fileno in readable:
                time.sleep(0.1)
                packet = self.read(260)
                break
        return packet

    def talk(self, packet):
        self._write(packet)
        responce = self._read()
        return responce

Thank you, Markus

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