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connecting 2 UARTs with 2 MAX232s ???

Discussion in 'General Electronics' started by Susanne Fischer, Jun 16, 2004.

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  1. Hi!

    I've got a problem: I have two evaluation boards here. One with a
    microcontroller and one with a Bluetooth-module. Both of them use UART
    and have a MAX232 already connected. This works well when connecting
    them to a PC.
    I would like to connect those 2 boards together in order to control my
    Bluetooth-module with the microcontroller. The problem is, that simply
    nothing happens (no matter what baudrate). I had such a problem
    earlier and found out, that when I remove both of the MAX232 it works
    well. Of course.
    Theoretically it should also work with two of the MAX232s. I have no
    possibility to leave them away on my board because I'm not allowed to
    modify them (by soldering...).
    Does anyone know, what kind of problem this could be? Maybe just some
    timeouts which cannot be reached when using 2 MAX232s?

    Thanks for your help in advance,
    Susanne Fischer
  2. Rich Webb

    Rich Webb Guest

    Google "null modem".
  3. Quack

    Quack Guest

    Try swapping RX and TX pins around.
  4. Quack

    Quack Guest


    If this is also your question regarding voltage, then ignore the
    zenner approach, you can connect them directly using the max232's.
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