library question

This is a discussion on library question within the C++ Programming forums, part of the General Programming Boards category; hello! i downloaded codeplug's code in the thread: http://cboard.cprogramming.com/showthread.php?t=47870 and tried to compile it. but when i executed it, all ...

  1. #1
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    library question

    hello! i downloaded codeplug's code in the thread:

    Simple RS232 Question

    and tried to compile it. but when i executed it, all i get is a black screen.

    i tried to replace the port value ith the available ports i have (1,5, & 6), but i still get the black screen. anyone know what's wrong with it?
    Attached Files Attached Files

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    Ask codeplug.
    dwk

    Seek and ye shall find. quaere et invenies.

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  3. #3
    Registered User Codeplug's Avatar
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    >> ...but i still get the black screen
    Is anything being sent to COM5 at 9600, "8N1"? If not, then all you should see is a black screen.

    What device are you trying to comunicate with?

    gg

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    i posted the wrong port.cpp file

    sorry! i misplaced the actual code i used. the actual code is attached below.

    i'm trying to communicate with com port 2. i have 2 Sfile objects (sf & sf2). sf writes a string into com 2 and sf2 is reading the previously entered string from com 2. please tell me what is wrong with my code.
    Attached Files Attached Files

  5. #5
    Registered User Codeplug's Avatar
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    * Open both ports at the same time. The Open() method purges the port.
    * Check for failure of the Read() and Write() methods.
    * Use a NULL-Modem cable to connect the ports.

    If you still having problems then you probably have a cheap UART chip on your motherboard. Some UART chips that drive multiple COM ports don't work when the ports are talking to each other with a NULL-Modem cable.

    gg

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    thanks!

    thanks for the suggestions! i think i understand it better now. i hope you don't mind, but i have question (i promise this is the last ).


    for example , i am writing a string to the port. so i write

    DWORD d;
    Write(str, sizeof(str), d ).

    is this right? or do i change something? i am not too sure what should be the value of the third parameter.

  7. #7
    Registered User Codeplug's Avatar
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    The last parameter is an output parameter that receives the number of bytes actually written. If Write() returns TRUE, then it's safe to assume that it wrote as many bytes as you told it to (the second paramter).

    I wrote that code back in '97. It's probably time for an overhaul.

    gg

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