Using Serial Port for Non-Serial Data Acquisiton

[MDMAXSON]

I searched the forums and couldn't find anything related to this topic.

I saw that it was possible to use the parallel port for simple digital I/O and I was hoping the serial port can be configured the same. It seems all the VISA VI's only want to use the serial port to recieve ASCII chars at a given baud rate, but is it possible to simply poll the status of the serial line at my own speed to see if it is high or low, kind of like a single pin DAQ?

It seems it would be possible as long as the serial data is read and controlled by labview and not by Windows. Let me know if you have any ideas how to approach this problem, or any feedback as to why it is not possible.

Thanks everyone!

[falkpl]

You can read and write teh high-low valuse of the status lines using a visa property node.  I have used this for triggering in the past.  Note that rs232 is not always consisnat in the voltage levels High is ~+3-12V and low is -3-12 volts.  What do you want to do with the port?

[MDMAXSON]

I threw down a property node and looked through the properties to select, but I couldn't find a status node to poll. I did notice there was a status VI under GPIB, but it takes in a string address instead of a COM port..... which I am unfamiliar with. Is this property node still available in 8.6?

The main reason for this VI is general single line signal monitoring. A lot of the times around the lab no scopes or DAQs are available, but serial cables are always on hand for quick use.

[MDMAXSON]

Disregard my last post. I found the VISA Status VI..... but when I link it to my serial COM port I only get error messages saying it is either not configured or in a conflicting state. How do I properly configure this VI for status polling?

[Dennis_Knutson · Accepted solution]

Select Property>Serial Settings>Modem Line Settings. For example, the CTS State is an input to the pc.

Using these lines is a very poor replacement for a scope or DAQ board. The only things you can get back is Asserted, Unasserted, or Unknown. The range of acceptable signals is quite large. Anything between +3 and -3 is an unknown state. Your other signals are +/3 to 15 volts. what kind of signals do you actually want to capture?

edit: There is no such thing as VISA Status so I have no idea what you are actually using.

Message Edited by Dennis Knutson on 07-20-2009 11:09 AM

[MDMAXSON]

Thanks Dennis, that worked out very nicely..... although its not going to work out too well since the logic low is -3V.

The method I was referring to was VISA Read STB... going back and looking at it more closely it was clearly not the VI I thought it was.

The reason I wanted this was mainly for things like triggering a program without a DAQ when timing isn't essential and counting pulses.