Acquiring data from external device that uses RS-485

[mcoursen]

I am currently using a 9174 cDAQ device.  I am trying to connect the cDAQ to an external source that communicates through a RS-485 serial cable.  I have spoken with a few representatives from Lawbview and they have told me that there is no direct way to talk to the chassis with the serial cable.  I must purchase a serial to USB-485 cable and communicate in parallel within LabView.  If I don't directly go through the cDAQ chassis, then why do I even need it?  And, I'm lost as in how I will communicate with an external source within Labview.

My second question.

I have a 9074 cRIO.  And, through much research, I have noticed that it seems to much easier to use this device for this situation.  My only problem is that I am new to LabVIEW and I feel that working with the cRIO may be a little difficult for me at this point.  My question is, would it be easier to perform the acquisition with the above set-up, or use the cRIO and spend a little extra time.

The application that i am trying to perform is this:

I have a RS-485 from the external source.  Then I want to stream 2048 byte serial data stream that is continuous into NI and have it look at the serial data and assign a Virtual LED on a graphic and/or a display message to tell me what's coming across the serial stream.

[JKMM · Accepted solution]

cRIO is definitely more complicated to get going that a USB-485 cable.  cRIO is meant more for embedded applications, not serial.  You also don't need cDAQ in the equation.  All you need is this:

NI USB-485

http://sine.ni.com/nips/cds/view/p/lang/en/nid/12845

Did someone recommend a cDAQ to you for this application?  cDAQ is an flexible data acquisition platform for reading raw analog and digital signals.  If your data stream conforms to the RS-485 standard, you don't want cDAQ for that.

I have attached an example program to get you started.  It's from the examples included with LabVIEW when you install the NI-VISA driver that supports serial communication with LabVIEW.  If you have NI-VISA installed it should show up in you NI Example Finder located from the top menu at Help>>Find Examples if you search for "serial".