Error: Analog Output underflow event
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I am trying to simultaneously record two analog inputs and create a digital output using a National Instruments DAQ. I cannot get around this error, however, and I have not found any posts that specifically address it. The most confusing part is that I am not actually using any analog outputs! The last valid output is always a little less than half of what it should be. For example, if the output signal is 1e6x1, then the last valid output scan number is 498552. Here is the code:
s = daq.createSession('ni');
Dch = addDigitalChannel(s,'Dev1','Port0/Line0','OutputOnly');
Ach = addAnalogInputChannel(s,'Dev1',0:1,'Voltage');
Ach(2).TerminalConfig = 'SingleEnded';
Ach(2).Range = [-5 5];
s.Rate = 250000/length(Ach);
ActualRate = get(s,'Rate');
L = 2; % number of seconds of each voltage pulse
TotalTime = 8; % total output signal length in seconds
n = TotalTime/L/2; % number of times to repeat a pair of pulses
tempOutputSignal = [5*ones(1,L*ActualRate) zeros(1,L*ActualRate)];
OutputSignal = repmat(tempOutputSignal,1,n)';
OTime = linspace(0,TotalTime,length(OutputSignal));
figure, plot(OTime,OutputSignal);
s.queueOutputData(OutputSignal);
duration = s.DurationInSeconds;
[data,time] = s.startForeground;
Update: I have worked on this issue through the National Instruments forum and can say with some certainty now that it is not a hardware issue, but is, in fact, an issue with the code. Please help!
3 个评论
cecile conrad
2022-5-2
@Sarah Miller / @Daniel did you figure out what the problem was? I have the same error and am not able to figure it out with the example listed below.
Eric Ng
2024-8-20,7:35
I somehow managed to avoid this by reducing the sampling rate. I suspect it has to do with PC/MATLAB not fast enough to grab data from NI due to whatever reason or NI has a miss. I did not have this issue when I used the USB 6366 version of NI till I migrated it to a CDAQ 9189 version. My CDAQ version should be more powerful in every aspect vs the USB version except for the very limited FIFO size vs the USB version.
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