VeriStand
Running DAQmx waveform in Veristand
So I assume what you're trying to do is similar to the "Cont Gen Voltage Wfm-Int Clk.vi" example (from LabVIEW's example finder), where you write a waveform to the task, start it, and then let it continuously generate:
Your specific implementation would be a little different than the above example, since you want the ability to change amplitude or frequency, and set a new waveform to be generating. To do this, you would stop the task, write a new waveform, then start the task again. Is this correct?
Read over the documents included in the Easy Custom Device .zip to get an understand of how to use the tool. In order to make your AO custom device with the tool, you would do something similar to the following:
Configuration Data: This would include any settings that you may want to make in System Explorer, but that don't need to be changed at runtime. This could include Physical Channels, Min/Max Values, Samples Per Buffer, Cycles per Buffer, etc... These settings will show up on the main page of your custom device.
Channel Data: These are things that the user reads or writes at runtime. In your case, you might have two Input Channels (Amplitude and Desired Frequency), and one Output Channel (Resulting Frequency).
Real Time System Data: This is data you pass between states of your code. In your case, I think this would just be the Task Refnum.
Init VI: In this VI you would create the task, generate the waveform (based on the default values for the freqency and amplitude channels), set the task timing, and write the waveform to the task (the first 4 VIs in the above example). The created task would be stored in the Real Time System Data cluster, and the Actual Frequency would be written to your output channel.
Start VI: This VI would call "Start Task" to begin generation of the initial waveform.
Execute VI: This is the VI that gets called repeatedly while NI VeriStand is running. This will be an asynchronous custom device, so the code won't actually run inside of the main VeriStand loop (and therefor you won't block execution if your code runs late). However, the main loop will communicate the channel data to your code every iteration, allowing you to respond to user input. Inside of this VI you will first check if the Amplitude and Desired frequency are the same as the previous iteration. If they are, this means that the user hasn't changed any inputs, and you should keep generating the existing waveform. So if the channels haven't changed, don't do anything else in this VI. This is similiar to the "Add" custom device example described in the "Example Walkthrough.docx" which is included with the custom device tool, where the file is only written to if one of the user inputs has changed.
If either of the channels has changed, this means that the user is requesting a new waveform to be generated. In this instance you would stop the task, regenerate the waveform, set the sample clock, write the waveform, and start the task again. This is basically the same as doing both the "Init VI" and the "Start VI" from above (except you don't need to create the task again).
Stop VI: This executes when the system is shutting down, so in this VI all you need to do is clear the task.
Hopefully that helps give you an idea of how to get started with your custom device. You might need to make some changes from what I described above, but it should be a good starting point. Hopefully it can help you adapt your existing code into the custom device template.
