Serial fread is too slow

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Nikolay Konstantinov 2018-2-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/382069-serial-fread-is-too-slow

评论： Tillmann Spellauge 2019-1-6

I'm using MATLAB R2017a & Linux.

    version -java
    'Java 1.7.0_60-b19 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode'

The program below, 75% of time spends onto fread(). How can it be speed-up?

        s = serial(serial_port,'BaudRate',baud_rate,'DataBits',8,'InputBufferSize',buffer_size); 
        fopen(s);   
        size_to_read=s.BytesAvailable;
        if (size_to_read>10)
            out = fread(s,size_to_read,'uint16')
            // some code //
        end

Probably direct access for Java will be faster, but I dont know how.

Another solution is use this MEX https://nl.mathworks.com/matlabcentral/fileexchange/62545-mex-c-serial-interface This output is 8bit digits, but I need 16 bit, can it be changed?

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Walter Roberson 2018-2-12

There is no problem using nested functions for callbacks or using shared objects with serial ports, and doing so is often a good structuring mechanism. Shared variables are one of the faster forms of variable access.

I notice that you are using // for comments. Those are not supported for MATLAB, which suggests you are possibly using Octave.

Tillmann Spellauge 2019-1-6

I have a similar problem.

I am using Matlab R2018b and linux. My program is spending 90+% of its runtime in "com.mathworks.toolbox.instrument.SerialComm". More specifically in the igetfield() function used in line 150 of the fscanf() function. It also makes no difference using fread(), fgets() or fgetl().

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