How can I acquire data in the background while writing data with a NI DAQ?

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Deryn LeDuke 2022-2-15

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https://ww2.mathworks.cn/matlabcentral/answers/1650515-how-can-i-acquire-data-in-the-background-while-writing-data-with-a-ni-daq

评论： Deryn LeDuke 2025-2-4，15:31

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Hi All,

I am interested in using a NI DAQ device for two main uses:

1) Send digital outputs at certain times to turn external solenoids on or off

2) Read voltage inputs in the background while I'm sending the digital outputs.

The code that I wrote works perfectly well to send the digital outputs, but fails when I try to read any voltage inputs. My suspicion is that matlab is getting confused as to which channels I'm using to record and which I am using to write, but I am not sure how (or if) I can specify which channels to read from and which to write from.

Below is the code that I have been working with:

%% Section 1: Establish device
d_list=daqlist("ni");
dq=daq("ni");
% We are going to use "Dev1" (USB-6211)
daqinfo=d_list{1, "DeviceInfo"};
dq.Rate=1000;
%% Section 2: Add inputs and outputs
ch0=addoutput(dq, "Dev1","port1/line0","Digital");
ch1=addoutput(dq, "Dev1","port1/line1","Digital");
ch2=addoutput(dq, "Dev1","port1/line2","Digital");
ch3=addoutput(dq, "Dev1","port1/line3","Digital");
[ch4,idx]=addinput(dq,"Dev1","ai0","Voltage");
% Establish Function for continuous background acquisition (function is defined below)
dq.ScansAvailableFcn = @(src,evt) reportWhenEqualsOrExceedsOneV(src, evt);
dq.ScansAvailableFcnCount = "auto";
% Start bacground acquisition
start(dq, "continuous");
%% Section 3: Write digital outputs (this is a simpler example of the code I'm running)
log=[];
for ii=1:20
 write(dq,[0 0 1 0]) % Write tone 1 
 pause(.250)
 write(dq,[0 1 0 0]) % Write tone 2
 pause(.250) 
 write(dq,[0 0 0 0]) % End tones
 log(ii)=ii;
end
% End background acquisition
stop(dq)
%% Section 4: Function section
function reportWhenEqualsOrExceedsOneV(src, ~)
    [data, timestamps, ~] = read(src, src.ScansAvailableFcnCount, "OutputFormat", "Matrix");
    if any(data >= 1.0)
%        disp('Detected lick exceeding 1V') 
        timelog=timestamps;
        datalog=data;
    end
end

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Arnaud Mahe 2025-1-23，15:12

Hello Deryn, I have the same issue as you. Did you solve this issue?

Deryn LeDuke 2025-2-4，15:31

Hey Nubia and Arnaud,

I was able to find a workaround to establish a parallel processing stream via MATLAB which collects NIDAQ data, but that does take up a lot of memory. The workaround that I did which is a little silly is to ask MATLAB to trigger a secondary collection script that I wrote via python, which collects serial monitor and camera information simultaneously with NIDAQ collection. I use physical voltage signals to sync these two data streams (one shared input between serial monitor and NIDAQ and camera triggers for frames). Because python uses serial communication, I can send an output, trigger the experiment, and then quickly reopen the connection to recieve inputs.

Other than using I2C communication (which would require a significant change to my circuitry, but might work for your circumstance), using this dual-language/parallel processing approach has worked well.

Hope this helps! I am happy to clarify if needed.

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How can I acquire data in the background while writing data with a NI DAQ?

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How can I acquire data in the background while writing data with a NI DAQ?

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