Get only numbers from serial port without any str2num() conversion

Question

Sergey Makovkin 2016-3-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/275418-get-only-numbers-from-serial-port-without-any-str2num-conversion

评论： Walter Roberson 2016-3-28

Hi all!

In the serial com port channel values comes from 0 to 1023, this example from Arduino: https://monosnap.com/file/TiTehc6zWhu0zszPnCALbnjIMAfpzf

On the MATLAB side I parse it via function:

function sPs = GetsP()
global obj1;
sPs = 0;
while(obj1.BytesAvailable)
    Psvoltage =  fscanf(obj1);
    if (~isempty(Psvoltage))
        sPs = str2num(Psvoltage) * (100 / 1023);
        break;
    end
end

But I dont like this variant, because str2num() conversion is very slow. If I try to use Psvoltage = fread(obj1, 1, 'ushort'); I didnt see correct data, because fread() reads binary data.

So the question is: How can I try to read direct number data, without any slow string to number conversion? How can I need to use fread() to get numbers?

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Sergey Makovkin 2016-3-28

Arduino outputs a fluorescence value from a photomultiplier tube via COM port. The image has been created on the scanner by this data. We design two-photon laser microscope for medical purposes, therefore, a very important data transmission speed. Slow place here is the serial port, but these are the conditions of the project.

Walter Roberson 2016-3-28

Reprogram the arduino code to send uint16 instead of text. You only need 10 bits of the 16, so you could even pack in some flags like "Beginning of Row" to help synchronize. Or you could take advantage of the extra 6 bits to add error correcting codes to make it easier to recover from potential dropped bytes.

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