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Discussion in 'Electronic Design' started by babu, Sep 12, 2007.

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  1. babu

    babu Guest


    I am new in serial port programming. I am currently doing a program
    that communicates to DSP board through COM1 port. But I am using
    Microsoft Visual Studio 2005. The language that I am using is C#. I am
    using the built in class SerialPort provided by Microsoft. When I send
    some bytes to the output buffer they always appear somewhat later at
    the input buffer...
    This is really frustrating.I know how to turn off the local echo in
    the Hyperterminal, but there seems to be no method for doing this in
    Microsoft Visual Studio.

    Please help me to resolve this problem

    Thanks in advance
  2. Paul Burke

    Paul Burke Guest

    Does the target board echo the characters?
  3. babu

    babu Guest

    As far as I read about read about that board it does not echo
  4. Paul Burke

    Paul Burke Guest

    Have you looked with a scope though? Don't spend time chasing a software
    problem until you're sure the characters aren't physically present at
    the input.
  5. Are you sure it is the serial?.
    If you are using a KeyPress event in a text box, to 'send' the serial
    data, this event, must be set as 'handled', or the default behaviour will
    be to type the character into the local text box, giving the same apparent
    behaviour as local serial echo.
    Just a thought.

    Other thought. How are you sending the data to the DSP?. If you are using
    a RS485 link, rather than RS232, these normally receive all data 'on' the
    link, when it is sent. Hence the sending board, will see the transmitted
    data, as well as any returned data.

    Best Wishes
  6. Depending on the hardware sometimes if you dont set
    SerialPort.DtrEnable property to true it may echo, but this it rare
    and is always immediate. I have also heard stories that using
    WriteLine() with certain modem commands (not the commands that force
    the modem to echo) can cause an echo. Failing that I would be looking
    at the device you are communicating with.
  7. Si Ballenger

    Si Ballenger Guest

    Disconnect the device from your serial port and see if the echo
    is still there.
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