How can I read data in backgorung from my NI hardware?

Hi, I would like to run "read" function once in background to collect data in one-second intervals, and foreground to collect data in 0.03 s intervals simultaneously. Unfortunately I can't do it. Matlab return message "Use of function cd is not supported on a thread-based worker." Can you plaese advise me some solution for my problem?

d = daqlist;

d(1, :)

d{1, "DeviceInfo"}

dq = daq("ni")

dq.Rate = 51200;

ch1 = addinput(dq,"Dev1", "ai0","Voltage");

ch2 = addinput(dq,"Dev1", "ai1","Voltage");

F = parfeval(backgroundPool,@background_FFT,2,t_fft);

%%first data acquisition for 0.03 seconds

for i=1:inf

data = read(dq, seconds(0.03));

end

function [FFT,fr]=background_FFT(t_fft)

dq = daq("ni")

dq.Rate = 51200;

ch3 = addinput(dq,"Dev1", "ai3","IEPE");

%second data acquisition for 1 second

for i=1:100000

data = read(dq, seconds(t_fft));

ch3=data.Dev1_ai3;

[FFT,fr]=widmofft(ch3,dq.Rate,t_fft,1);

plot(fr,FFT)

end

Thank you.

Answer 1

[Jeffrey Clark]

@Jan Tomaszewski, try moving the device setup into your main program and pass that dq (and maybe ch3) as a parameters to the worker to use. Others have seen this issue with using files (opening) in workers and it seems likely that external devices could fall into that category see. But after the connection is made perhaps it would work. See:

readstruct getting error when attempt to run function in background - Help Center - MATLAB & Simulink (mathworks.com)