Generate sine waveform (myRio)

Question

What is the best way to generate a 1khz sine signal on one of the analog outputs of the myRio device? I tried a timed loop and the Point by Point Sine Generation VI similar to the Electret Microphone demo or this post: http://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/frequency-matching-problem-with-myrio/m-p/2... by Sammy_K. But the resolution is a problem. The frequency is not very accurate and with a dt of 100 uS and a 1Mhz Clock I only get 10 samples per period. A dt of 10 is too much load for the processor (the deivce does not respond anymore and needs to be restarted). Is there a better way of generating a 1khz sine output or do I need to do this within the FPGA somehow?
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Answer 1

Hey JulianR,
The thing to keep in mind is that each time you call the Analog Write express VI you write one data point to the analog output on the myRIO.  The rate at which data is output is determined by the rate at which you loop runs.  You can use a timed loop in LabVIEW to write analog output values at a relativly fixed loop rate and vary the value to generate a sine wave output.
I put together an example of doing just this (but using the value to set a PWM duty cycle rather than analog output) in this thread.  You'd basically need to replace the PWM express VI with the Analog Output Express VI.
Finally as Marc67 mentioned you could implement the sine wave output in LabVIEW FPGA which would give you more control and let you use faster output frequencies.  I'd start with the timed loop method and move to FPGA if you need faster output rates.
Let us know if you have more questions for us.
-Sam K
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