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： Nubia Mendes 2022-3-16

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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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Nubia Mendes 2022-3-16

Hi Deryn, have you been able to solve this? I'm have the exact same issue where I'd like to read force signals continuously and write voltage to the DAQ under certain conditions.

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