Generating two different frequencies with NI-DAQ 6251 Analog output

Question

signal 2011-11-9

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/20712-generating-two-different-frequencies-with-ni-daq-6251-analog-output

Hi,

I want to use my DAQ as a function generator to generate two different frequencies continuously. A simple code like

ao= analogoutput(adaptor, deviceId);
addchannel(ao, 0:1);
nsample1 = freq1/sampling_rate
nsample2 = freq2/sampling_rate
wave1 = sin(linspace(0,2*pi,nsample1));
wave2 = sin(linspace(0,2*pi,nsample2));
set(ao,'RepeatOutput',inf);
putdata(ao,[wave1' wave2']);

won't work because [wave1' wave2'] are of different lengths. I can't pad any data to the end of the shorter wave because if the two frequencies are relatively prime, one of the would not be periodic.

Is there anyway around this?

Thanks!

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Answer 1

Walter Roberson 2011-11-9

1
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https://ww2.mathworks.cn/matlabcentral/answers/20712-generating-two-different-frequencies-with-ni-daq-6251-analog-output#answer_27343

You are not required to output to both channels simultaneously. If the job works better by separating the channels, do so. This might cause a lag between the two. If the lag gets to be too much, then adopt another method.

You can use lcm (Lowest Common Multiple) to determine how many of each side you need you would need to queue so that the queue would have full cycles for both waves.