Updating waveform chart continuously with digital i/o

[was1984]

I'm new to Labview and I'm trying to output a digital waveform graph to update in real time after parsing out some data from a digital DAQ input.  Is this possible or can real time updating only be done with charts?

[alpha1 · Accepted solution]

Hi,

A very similar topic was once discussed in the LabVIEW forum, where DFGray answered the following:

1. You can use an XY Graph by generating the X values yourself. This will ensure that you place the data exactly where you want it on the X axis. This is fast, but does involve a memory cost.
   
   
2. You can use a Waveform Graph with a waveform input instead of the cluster you are using. Use the Build Waveform primitive instead of the bundler to make your waveform. Set the t0 values to the appropriate values (negatives do work, as do small numbers - time is in seconds, use the To Time Stamp primitive to convert from DBL to timestamp). Finally, you need to set the Waveform Graph to use the t0 values. Pop up on the Waveform Graph and make sure Ignore Time Stamp is not checked. Depending on your version of LabVIEW, you may have to pop up on the graph or the axis. When you unselect Ignore Time Stamp, you will probably want to reformat the X-axis again. The Waveform Graph clears data at each iteration, so you will need to replot all your data each time. Just create an array of waveforms and keep adding to it. The t0s will put the waveforms in the right places. Yes, this may cause memory problems.
   
   
3. Finally, you can use the Waveform Chart, which does have memory. Create the waveforms like you did for the Waveform Graph and send them to the chart. It will remember what was sent to it from run to run. Make sure you set the Chart History Length (pop up on chart and select Chart History Length...) to long enough to hold your entire data. You can use a property node to get the data back at the end, if you need to.

Link to the original thread: http://forums.ni.com/ni/board/message?board.id=170&requireLogin=False&thread.id=102699

I hope this solution solves the problem.