Generating 500 kHz Signal in C++

[C. Drutman]

I am just starting with the MCC Library with a USB-2627, and my goal is to generate a 500 kHz sin wave as a simple sanity test. My first step was to verify I could output a signal with AOut, and that worked as advertised. I then changed the signal-generating part of the code to:

 

double f=.5E6 ;

double w=6.283*f ;

double dt=1.E-6 ;

double t=0 ;

double data=0 ;

while (err == ERR_NO_ERROR) {

  data=sin(w*t) ;

  err=ulAOut(hdnl, channel, range, flags, data) ;

  t += dt ;

}

When I looked at the signal on a scope, I got a ~10 Hz sin wave, so clearly I am missing something. Looking at the documentation for the USB-2627, there is a reference to setting the sampling rate; is that what I am missing? If so, what is the MCC Library call to set this?

FYI, I am using GCC on Linux.

Many thanks.

 

 

[JRys]

A 500k Hz sine wave is not doable. This is because the analog outputs on your board have a maximum update rate of 1M S/s and a decent sine wave should have at least 100 updates per cycle. If you use this rule of thumb, the maximum sine wave possible is 1 M S/s divided by 100 or 10k Hz. If you are still interested in generating a waveform, please review the AOutScan.c example. 

[Fausto]

https://github.com/mccdaq/uldaq/blob/master/examples/AOutScan.c

 

[C. Drutman]

On 12/8/2022 at 11:51 AM, JRys said:

A 500k Hz sine wave is not doable. This is because the analog outputs on your board have a maximum update rate of 1M S/s and a decent sine wave should have at least 100 updates per cycle. If you use this rule of thumb, the maximum sine wave possible is 1 M S/s divided by 100 or 10k Hz. If you are still interested in generating a waveform, please review the AOutScan.c example. 

Not quite what I am looking for. I am receiving data from a device, and based on that data I need to generate an analog output. The input data is updating every 10 us, and I need to generate an analog output at the same rate, with a slight lag for computing the analog output from the input signal. Filling a buffer, as in AScanOut.c, is not an option as a I only have a single input at a time. Based on the test I did, I cannot send single analog outputs quick enough.

Edited December 29, 2022 by C. Drutman
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