When I started with LabVIEW, the first program I was tasked with maintaining was a LabVIEW 7 "Real-Time" routine written several years earlier (probably in a previous version of LabVIEW) and all of the I/O was "Traditional DAQ". It was so confusing and complex that I couldn't even get the Code Maintainer (who was mentoring me in learning LabVIEW) could explain it. I found an NI person who was visiting a nearby University to meet with me to give me a "crash course" in Traditional DAQ, and his advice was the following:
- Figure out the intent of the Traditional DAQ code, for example, "Acquire A/D samples from Channels 1-8 of a Multi-function PXI Module at 500 Hz, ±10V, continuous sampling, until I signal to stop.
- Learn DAQmx and simply write the DAQmx code for doing this.
At that time, there weren't as many excellent introductions to DAQmx as there are now. My all-time favorite is "Learn 10 Functions in NI-DAQmx and Handle 80 Percent of your Data Acquisition Applications" (if that is not the exact title, it is close enough for you to find it with a Web Browser). Ignore (please!) the first step, which mentions the Dreaded DAQ Assistant -- try to avoid (almost) all Express VIs.
Another hint is to "learn how your DAQ Device Works" by connecting it to your LabVIEW system, opening MAX, finding your device, and setting up a Test Panel to do whatever you want to do programmatically (such as sample A/D from Channels 1-8 of a particular piece of hardware plugged into your PC). You'll set it up, then you can get MAX to run it and you can actually acquire (and visualize) the data. If you now save this task in MAX, you have the perfect 3-4 DAQmx function routine that is described in "Learn 10 Functions", namely DAQmx Start Task (with a Task Constant wired to the upper left input, opened, and the MAX Task you saved chosen as the Task to run) wired to a DAQmx Read inside a While Loop (with viewing the data in a Chart or numerically inside the loop) followed by a DAQmx Stop Task outside the loop. Very simple.
Bob Schor
