connecting 2 UARTs with 2 MAX232s ???

[Susanne Fischer]

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

 

[Rich Webb]

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?

Google "null modem".

 

[Quack]

Try swapping RX and TX pins around.

 

[Quack]

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

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