Fread com device too slow

Question

Jason Riley 2021-1-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/725137-fread-com-device-too-slow

评论： Jason Riley 2021-1-28

Hi,

So I am currently using matlabd to read continuously from a device set um on COM4.

the device is streaming 5 32Bit Ints @4kHz. If i acquire data for say 4 seconds i appear to be waiting a further 7 or 8 seconds for the fread() function to catch up. any thoughts on how to speed this up as this delay is problematic when trying to acquire multiple scans, i am waiting longer than i am scanning.

Cheers,

Jason

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Answer 1

Vimal Rathod 2021-1-28

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链接

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https://ww2.mathworks.cn/matlabcentral/answers/725137-fread-com-device-too-slow#answer_608218

Hi,

Refer to the following existing solutions,

Fread performance is slow. Why? - MATLAB Answers - MATLAB Central (mathworks.com)

Serial fread is too slow - MATLAB Answers - MATLAB Central (mathworks.com)

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Jason Riley 2021-1-28

i don't see solutions in these only commentries, could you be more specific when you say use these solutions? these appear as discussions without answers.

I know uaing standard usb serial data readers that i can run at ful speed, but matlab seems slower.

here is the specific code:

set(app.obj1, 'ReadAsyncMode','continuous');

done=0;

while (done==0)

if app.obj1.BytesAvailable>0

while app.obj1.BytesAvailable>0

values(1,1)=fread(app.obj1,1,"uint32");

values(1,2:5)=fread(app.obj1,4,"int32");

Values=[Values;values];

done=1;

end

stopasync(app.obj1);

currently the device streams 5x32bit numbers at 4kHz. if i scan for 2 seconds, i currently wait 4-5s for the buffer to catch up. Given using other streaming programs i have 0 wait time, i assume there is some paraemter which needs to be set in matlab to make this run faster? but as to what, i find no answers in your suggested reading.

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