delay getdata, start(analoginput)

Jonas — Mon, 28 Sep 2009 15:27:02 -0400

Hi, I'm using the data acquisition toolbox to continuously sample from an analog input channel of a National Instruments card. However, there seems to be a varying delay of at least 40 ms between signal change and matlab response. This is due to the functions "start(ai)" and "getdata(ai)". Is there a way to speed up the acquisition, maybe by changing the analog input object configuration? My current configuration is as follows:

SampleRate: 10000
SamplesPerTrigger: 2

I'm looping through following code:

                start(ai)
                pause(0.001);
                data = mean(getdata(ai));
                stop(ai)

Thx for any response.

Jonas

Re: delay getdata, start(analoginput)

Sherryl Radbil — Tue, 29 Sep 2009 12:43:04 -0400

Hi Jonas,
Rather than stopping and restarting the analog input object, which will introduce the delay you are seeing, use callbacks which you can begin learning about here:
http://www.mathworks.com/access/helpdesk/help/toolbox/daq/f9-34753.html

Pay particular attention to the Timer and SamplesAcquired events.

All the best,
Sherryl

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delay getdata, start(analoginput)

Re: delay getdata, start(analoginput)