How can I change the buffer size on NI-Daq device, using session-based interface ?

Hello, I'm using the session-based interface to acquire datas from an NI-USB Daq-device. I'm processing datas during acquisition, using a listener. I would like to change the length of the events, recieved during acquisition. In this exemple, would it be possible to change the size of event.data, recieved in the function plotData ?

s = daq.createSession('ni');

addAnalogInputChannel(s,'cDAQ1Mod1', 'ai0', 'Voltage');

lh = addlistener(s,'DataAvailable', @plotData);

 function plotData(src,event)
     plot(event.TimeStamps, event.Data)
 end

Thank you,

Answer 1

[Shyam Sangaraju]

You can use “getdata” function to acquire data of specific size. Following sample code demonstrates how to use “getdata” function:

>> ai = analoginput('nidaq','Dev1')
>> addchannel(ai,0);
>> set(ai,'SamplesAcquiredFcnCount',4)
>> set(ai,'SamplesAcquiredFcn',@mydaqcallback);
Where @mydaqcallback consists of the following code:
function mydaqcallback(obj, event)
% number of data samples to acquire
data = getdata(obj,obj.SamplesAcquiredFcnCount);
% you can execute your logic here.

Where ‘obj’ is an analog input object.

‘obj. SamplesAcquiredFcnCount’ is number of samples to extract.

‘data’ is m-by-n array, where m is the number of samples extracted and n is the number of channels contained by obj.