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POContinuously acquire data in MATLAB using callbacks and persistent variables
 

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  1. POContinuously acquire data in MATLAB using callbacks and persistent variables
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    <p>I have just recently started to use MATLAB to acquire data off of a data acquisition board and was in need of a function to acquire data continuously (i.e. until I ctrl^C out of the function). To do this I am using the data acquisition toolbox on a 32-bit windows OS.</p> <p>Based on the documentation in matlab help and a few of the answers on this site, I found that after adding channels to my input handle I should:</p> <ol> <li>set my 'SamplesPerTrigger' to Inf</li> <li>set the 'TimerPeriod' to some value to trigger the 'TimerFcn'</li> <li>set the 'TimerFcn' to some subfunction callback which appends data to a persistent variable</li> </ol> <p>Is this a correct way to do this?</p> <p>My code is as follows:</p> <pre><code> function acquire_arena_test(samprate,daq_device ,device_ID ,channels, saveroot) setup.SampleRate = samprate; setup.DAQdevice = {daq_device, device_ID}; setup.AIChannels = channels; setup.SaveRoot = {saveroot}; ai = analoginput(setup.DAQdevice{1},setup.DAQdevice{2}); addchannel(ai,[setup.AIChannels]); set(ai,'SamplesPerTrigger',Inf); set(ai,'TimerPeriod',0.5); set(ai,'TimerFcn',{@AcquireData,ai}); start(ai); while(strcmpi(get(ai,'Running'),'On')) pause(1) end stop(ai); time = datestr(now,30); save([saveroot time], 'data'); delete(ai); clear ai; function AcquireData(hObject, ~) persistent totalData; data = getdata(hObject); if isempty(totalData) totalData =data; else totalData = [totalData; data]; end </code></pre> <p>The initial analog input is definitely working properly. I have tried <em>many</em> permutations of giving the AcquireData callback to 'TimerFcn'. The error I receive is </p> <p>`??? Error using ==> acquire_arena_test>AcquireData Too many input arguments.</p> <p>Warning: The TimerFcn callback is being disabled. To enable the callback, set the TimerFcn property. `</p> <p>Thanks in advance for any help.</p>
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    1. COMy call to the function is `acquire_arena_test(1000,'nidaq','Dev1',[0:7], 'C:\....\')` after running `daqreset` and `clear all`. The 8 channels do receive input, because if I comment out the 'SamplesPerTrigger' I get an output file saved in my saveroot.
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