Serial Port Communication

[Kura]

I'm trying to write a program that sends a signal to the serial port every few seconds, but all I want it to signal is pin 3 and I think pin 7, what is the correct procedure for only sending a signal to certain specified pins? If anyone can help the help would be greatly appreciated.

[jbrohan]

If you are writing only then you need only pins tx and gnd to be wired to your equipment. The serial routines work fine without the RX pin wired. Actually I’ve done this only with the old direct serial writes I just have not done it with VISA, but it’s likely to work.
Yours Sincerely
John www.tradersmicro.com

[Dennis_Knutson]

I've done it VISA and transmit only works fine. Pin 7 is RTS (Request to Send) and that's normally set with a handshaking mode but can be manipulated manually with a VISA property node (modem line settings).

[Kura]

I'm confused.... what menu do I look under to find a direct serial write? Or is VISA the only method now?

[Ricardo_SR]

Hi Kura,

The old serial VIs were used in old LabVIEW versions. If you have LabVIEW 7.0 or 7.1 you need to use the VISA VIs to communicate to the serial port. Now, if that is the case, the best solution is what Dennis suggested. You can find that property node in the VISA Advanced tools palette.
Hope this helps

Ricardo S.
National Instruments.

[Kura]

Okay but I'm still confused. If I want to send a signal to just pin 3, how would I do that? I've found something along the lines of 50 different settings on the property node and am still no closer to wiring a command to send a signal to pin 3 😕 Any further help would be greatly appreciated.

[shoneill]

Using VISA, you're a little bit limited which pins you can monitor / set. If you find you can't set /control one of the pins you want, simply make an adapter for the cable to "convert" pin 3 on your instrument side to a pin which you can control from VISA.

To control the lines, you need to open a VISA session on the required serial port, and then using the VISA property node, you can access the individual lines of the COM port. Setting them to 0 and 1 controls the signals on that line.

Hope this helps.

Shane.

[Ricardo_SR]

Hi Kura,

I saw the other post you did that you cannot even do a normal serial write. First I would make sure that you can do that by reinstalling VISA which seems to be the problem right now. Then, if you disable the handshaking then the rest of the pins should be disabled.
Let me know if this helps.

Ricardo S.