Using fread to read streaming binary data from ethernet using Instrument Control Toolbox

Question

James Watson 2012-4-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/36093-using-fread-to-read-streaming-binary-data-from-ethernet-using-instrument-control-toolbox

My data are uint8 format. The documentation for fread seems to imply that the "precision" argument can set the output format of fread. But if I try to use precision='*uint8' or 'uint8=>uint8' I get an error. The default output is double, which takes too much memory. I've been using

Output=uint8(fread(TcpipObj,SIZE,'uint8'))

which works, but I'm guessing this generates a large array of doubles then converts to uint8.

My instrument streams data until the buffer is full, so I set up TcpipObj.InputBufferSize to pull in the data I need. I then set SIZE to the same value. I'd like to pull in 40 MB or so, but get a java heap memory error.

Suggestions?

Jim

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James Watson 2012-4-24

I seem now to have a hardware problem that's preventing me from reproducing the error and giving you a look at it. I'll try to reply when I get that squared away.

James Watson 2012-7-18

My instrument is back from repair! The error I get is Java exception occurred: java.lang.OutOfMemoryError: Java heap space at com.mathworks.toolbox.instrument.InputBuffer.getDataFromBuffer(InputBuffer.java:705) at com.mathworks.toolbox.instrument.InputBuffer.getDataWithInfo(InputBuffer.java:528) at . . . plus several more lines that I can type out if anyone is interested.

It appears that fread in basic Matlab and fread in the instrument toolbox are different functions with different input variables allowed.

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