How to acquire and generate data using NI DAQ simultaneously on a continuous basis

I have an NI input (9205) and NI output (9263) modules. I am trying to acquire and generate data in the same session but on a continuous basis. In this regard I referred to the tutorial provided for simultaneous acquisition and generation.

http://www.mathworks.com/help/daq/examples/acquire-data-and-generate-signals-at-the-same-time.html

However when I try to do this on a continuous basis that is for an infinite amount of time I get the error : The data argument must contain one column for each output channel in the session.

I have pasted the code below.

    function acquire_generate
clc;
global indata;
global outdata;

   s3= daq.createSession('ni');
ch1= addAnalogInputChannel(s3,'cDAQ1Mod2','ai19','Voltage');
addAnalogOutputChannel(s3,'cDAQ1Mod7','ao0','Voltage');
ch1.InputType= 'SingleEnded';

s3.IsContinuous= true;

 lh= s3.addlistener('DataAvailable',@plotData);% to plot acquire data in real time

 s3.NotifyWhenDataAvailableExceeds=1000;
outdata= indata/2;

 queueOutputData(s3,outdata);

 lh1=s3.addlistener('DataRequired',@queueMoreData); % adding a listener to queue output data continuously

 s3.startBackground();

 while s3.IsRunning % to prevent Timeout
pause(0.5); 
end

 close(gcf);
figure(1);
plot(indata);
figure(2);
plot(outdata);
end

 function plotData(src,event)
persistent localData;

 global indata;

 if(isempty(localData))
    localData=[];

    disp('acquiring starting');
end

 plot(event.TimeStamps,event.Data);
localData= [localData;event.Data];

 indata= localData;

if(max(event.Data)<5);

    disp('Stopping acquire')
    src.stop()
    plot(event.TimeStamps,event.Data);

end

end

 function queueMoreData(src,event)
global outdata;
queueOutputData(s3,outdata);
end

I am unable to figure out what I am doing wrong. Comments and insights will be appreciated. Thank you.

 Regards,
 Sri

Answer 1

[Michael]

I was having a different problem where I couldn't acquire for more than a few seconds.

for your problem, Srikrishnan, I'd start with the change below

ch(1) = addAnalogInputChannel(s3,'cDAQ1Mod2','ai19','Voltage');
ch(2) = addAnalogOutputChannel(s3,'cDAQ1Mod7','ao0','Voltage');

I was able to find that on Acquire Data and Generate Signals Simultaneously they say "When the session contains output channels, duration and number of scans become read-only properties of the session. The number of scans in a session is determined by the amount of data queued, and the duration is determined by s.ScansQueued/s.Rate.

Playing around with s.NotifyWhenDataAvailableExceeds fixed my problem.