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Serial port question

Discussion in 'Misc Electronics' started by CWatters, Feb 16, 2004.

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  1. CWatters

    CWatters Guest

    I've got a very simple application involving a PC transmitting (only) to a
    display over RS232. In theory only two wires are required Tx and Gnd as the
    display can "keep up" with whatever data rate the PC can produce. I'm using
    a test program that has the following handshake options "None, XON/XOFF,
    Hardware etc". I'm assuming that if I select "none" then the test program
    won't use handshaking but what about the UART itself?

    Does the UART in a PC need hardware handshake lines pulled to a particular
    state in order to transmit?
     
  2. Mjolinor

    Mjolinor Guest

    No, in my experiance it will work with all the other lines floating.
     
  3. Norm Dresner

    Norm Dresner Guest

    The protocols (both hardware and software) that govern PC serial
    communications are *all* dictated by the software. The UARTs themselves are
    just reporters of electrical facts.

    Norm
     
  4. ------------
    If you bit-bang the port IO itself, no, but if you use the BIOS, then
    yes, you'll need the DSR and CTS to be fooled because the BIOS will
    require it.

    -Steve
     
  5. CWatters

    CWatters Guest

    Thanks for all the replies. I finally figured out that the display I was
    driving needed a higher voltage power supply.

    If anyone else needs a simple app to test a serial port device then I
    recommend "Serial Device Tester" by Hack Consulting at
    http://www.hackconsulting.com
     
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