sending data using TXD, RTS, DTR line of the serial rs232 port

[peanuts]

hello

I've another problem using the serial port for data output:

The problem is that I have to confirm each bit (high/low) sent out of the TXD
pin with a high state on the DTR line (like a clock). After sending one byte I have to set the RTS Pin on level high.

I know that I can access DTR and RTS by using property nodes but I need a third line for my data output.


Thanks in advance
Simon

[Chris_Rake]

DTE ports (like the built-in COM port) have three drivers: TX, RTS, and DTR. It sounds like you're not using the TX in a normal way, so perhaps you can manually drive the TX line through the break state? Set break will drive a space ('0', or positive voltage) on the line, and clear break will drive a mark ('1', or negative voltage).

[peanuts]

thanks for your answer Chris

that was it - I've tried many things and had given up hope that this kind of communicanication (which is indeed not the one the serial port is intended for) could be realized simply using labview. Therefore I had already started to write some external C code - Your hint brought me back to G. And the programm is running pretty well meanwhile.

thanks again
Simon

[Chris_Rake]

I'm glad to know it is working. Just out of curiosity - how fast are you able to manually drive data using this method?

[peanuts]

I'm using a shift register to extend the three drivers of my rs232 port to eight.
TXD is sending out my data serially and the bits are shifted by the DTR line. When the
program has finished to send one byte I'm setting the RTS line to enable the output latch of the register.
Fairly easy if one knows how to set the "third output line":-)

Maybe this method is not suitable for high data rate communication but I just have to control some output states.
To he honest it's a little bit like abusing the com-port but for my special purpose it's working pretty well.

Simon