PySerial and termios

Discussion in 'Python' started by a b, Nov 30, 2009.

  1. a b

    a b Guest

    I have a pain in the a** problem with pyserial- it works 90% of time
    but on the 10% of time it thorows and termios.error exception with the
    value (5, 'Input/output error') and i cannot get rid of it :(
    The system works as follows:
    A device sends out rs485 data -> rs485 to rs232 converter converts it -
    now it hasn't bothered me too much since it hasn't been a lot of data
    (every time i get this exception i unload the pl2303 module from
    kernel, then reload it, open the com port and hope it won't happen
    soon). But now the amount of data is getting bigger and the exceptions
    in the log are quite bothering already so if anyone has a good idea
    what could affect it i'd be very glad...
    oh and the settings for the port opening are:
    self.ser = serial.Serial(self.port, self.baudrate, rtscts=0,
    xonxoff=0, timeout=0)

    With best regards,
    a b, Nov 30, 2009
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  2. Did you try a different usb2serial-converter? I've got plenty of them used
    in the past few years, and frankly, they mostly suck. Big time.

    With them, all kinds of timing-issues and other problems arose, and some
    hardware refused to outright work with them.

    So, I suggest you try & get a hold on as many usb2serial-converters you can
    get from friends and colleagues, and try out which one works best.

    There is nothing on the software-side you can do (short from lowering the
    bps, as this might cover up for some issues due to relaxed timing. But I
    had to cut down to like 2400 bps or some crap like that, which isn't really

    Diez B. Roggisch, Nov 30, 2009
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  3. Sounds like faulty converter or a bug in the device driver to
    Does that get rid of the error? If so, then it's definitely a
    problem with the converter or device-driver.
    Unless you want to try to troubleshoot the device driver and
    USB traffic, the only suggestion I have is to try different
    converters and/or different versions of the driver.
    Grant Edwards, Nov 30, 2009
  4. a b

    Glazner Guest

    Try to use Portmon to see if your data is sent correctly.(if not, then
    its the cable/converter)
    or another port monitor tool for other OS.
    Glazner, Nov 30, 2009
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