Error on queueOutputData(): The data argument must contain one column for each output channel in the session. Taking Transpose of dataOut gives same error.

Hello all,

I have been working for some time now to understand and fix an error I keep getting in MatLab. I keep getting the error mentioned in the title. I will paste my code below... Basically I have an output (controls a flashing LED) which is split with a BNC T splitter into an Input on a different DAQ. All I want to do is be able to output two graphs that are exactly the same... one from the output, and one from the input.

Through my searching online I found the solution of simply taking the transpose of dataOut (or AnalogOut1 in my case), and this did not work. To try and understand the issue more, I made some simplified dummy code that has a separate input and output. I was able to get to the same error, and in this case taking the transpose of dataOut worked perfectly. However this does not work within the code I need to get working (below).

I am thinking it may have to do with DataVec, however I am relatively new at MatLab, so troubleshooting this myself is proving quite difficult. (I'm using the NI PCI-6733, and NI PCIe-6323).

Thanks for any help....

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function AnalogInputTest(ST)
% ROIs should be

%%Scanning Variables
numLED=1;                           % number of channels (LED num + opto laser)
TExp=0.0085;                        % use to set frame rate, affects period of trigger pulse
FR=round(1/TExp);                   % frame rate
NumFrame=round(FR*ST);              % calculated total number of frames
%%AO control
outV=5;     % output trigger height (volts)
Sr=10000;   % sampling rate
s=daq.createSession('ni');
s.Rate = Sr;
Ar = s.Rate;
addAnalogOutputChannel(s, 'Dev1', 'ao1', 'Voltage'); % Blue LED (TL 470)
ch2=addAnalogInputChannel(s,'Dev2','ai0','Voltage');
s
%%Adaptive Control MatrixG

LEDtime=round([25]); %Blue, Yellow Orange, Red

SpF=floor(Ar/FR);        %samples per Frame (or per LED)
clear DataVec
DataVec=zeros(numLED*SpF,size(s.Channels,2));

for n=0:numLED-1
    DataVec((1+n*SpF+round(SpF./2-LEDtime(n+1)./2)):(1+n*SpF+round(SpF./2+LEDtime(n+1)./2)),n+2)=1;
end
%%Concatenate Everything Together
DataVec=outV*DataVec;
DataVecOff=DataVec;
AnalogOut1=repmat(DataVecOff,round(ST*Sr/(numLED*SpF)),1);
[time] = size(AnalogOut1,1);
%%to TTL Voltage
numtrig=size(find(AnalogOut1(:,1)>4.5),1);
numtrig=numtrig/LEDtime;
%%Begin Scanning
disp('Press ENTER when ready to start flashing sequence.')
pause
disp('Playing encoding sequence.')

queueOutputData(s,AnalogOut1');
data=startForeground(s);

[ch2,time] = s.startForeground();
plot(ch2);
plot(data);

release(s);

Answer 1

[Walter Roberson]

You have one input channel and one output channel, so

DataVec=zeros(numLED*SpF,size(s.Channels,2));

will be something-by-2.

You have

numLED=1;                           % number of channels (LED num + opto laser)

for n=0:numLED-1
    DataVec((1+n*SpF+round(SpF./2-LEDtime(n+1)./2)):(1+n*SpF+round(SpF./2+LEDtime(n+1)./2)),n+2)=1;
end

With numLED being 1, then that is n=0:0, and the n+2 takes that to offset 2, so you are writing into DataVec(:,2), so DataVec will certainly have (at least) 2 channels.

Your

AnalogOut1=repmat(DataVecOff,round(ST*Sr/(numLED*SpF)),1);

is not going to change the number of output columns, so AnalogOut1 is going to have two output channels.

You

queueOutputData(s,AnalogOut1');

which would be queuing 2 x something. Without the ' (which appears to be an attempt to get the code to work) that would be something x 2.

However: you need to queue with one column for each output channel, not with one column for each channel including input channels.

queueOutputData(s, AnalogOut1(:,2:2+numLED-1))

[Trevor Voss]

Thank you so much for the help!

Using this new queueOutputData() has fixed the error mentioned! Thank you for also explaining the use of columns and rows. This will help me not make this mistake in the future.

So now I am getting another small error on [ch2,time]=s.startForeground(); "There must be data queued in the session before this function can be called."

How do I queue the input data? I thought this could not be done like with OutputData.

[Walter Roberson]

I would have thought that the queueOutputData that you have would be sufficient for that. Did you happen to remove that call?

[Trevor Voss]

I actually moved from using queueOutputData(s,ch2); to [ch2,time] = s.startForeground(); due to one of MatLabs tutorials.

When I use [ch2,time] = s.startForeground(); I get the error "There must be data queued in the session before this function can be called."

However when I use queueOutputData(s,ch2); I get the error "The data argument must contain mxn real numeric values, where m is the scans to output, and n is the number of output channels in the session." Which happens for both (s,ch2) and (2,ch2').

[Trevor Voss]

So now for that last section of my code I have what is posted below.

Note that the [ch2,time] = startForeground(s); line is currently commented out.

I changed the analog input one to startBackground. This makes sense to me, because it needs to be recording data while I am outputting data. So recording should happen in the background, while the output happens in the foreground.

However I am still getting error: "The data argument must contain mxn real numeric values, where m is the scans to output, and n is the number of output channels in the session." on the line "queueOutputData(s,ch2);"

So this seems like a similar problem from before.

%%Begin Scanning
disp('Press ENTER when ready to start flashing sequence.')
pause
disp('Playing encoding sequence.')

queueOutputData(s,ch2);
%[ch2,time] = startForeground(s);
startBackground(s);

queueOutputData(s,ch1(:,2:2+numLED-1));
startForeground(s);

release(s);

end

[Walter Roberson]

I am not sure what ch2 is initialized to in this code?

I do not see why you have a startForeground while the background is active?

[Trevor Voss]

ch2 is the analog input channel.

Maybe this is due to me not understanding MatLab. I want to input the same data that I am outputting so in the end I will have a channel outputting data into an input channel. I then want to plot both what it is outputting and inputting, to then show they are the exact same graph.

I did the background/foreground thing so that way the input would be taking in the data at the same time as the output is sending it out. I read somewhere that MatLab will stop everything else while it is doing foreground data, so I wanted the other data to be happening at the same, so I figured having it go in the background would do this.

[Walter Roberson]

You cannot queue a channel; you have to queue specific data.

Have you arranged some kind of hardware loopback on your output to feed it into your input? Or do you want to configure the device to loop back (which is possible in at least some of the compacDAQ series chassis) ?

[Trevor Voss]

I have the output split and plugged into the input of a separate DAQ.

[Trevor Voss]

I see now that the whole foreground/background thing starts everything. Turns out I just thought it was more complicated than it was. I just used data=startForeground and then plot(data). Super simple. I hope this helps anyone else having similar issues. Thanks so much for your help.