Serial Port opening problem

Question

Abdel Rahman Bekawi 2019-11-4

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/489171-serial-port-opening-problem

评论： Abdel Rahman Bekawi 2019-11-5

I'm trying to acquire values from a microcontroller using the serial port. However, I'm facing a strange bug!

when I try to run the program for the first time it works and when I try to run it again it gives me an error saying that cannot open the port! But if I close matlab and open it again and run the program it works for the first time only and then same problem arises!

Can anyone help me please ?

Thanks in advance

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Abdel Rahman Bekawi 2019-11-4

I will try then to remove try and catch and close after my code is done and see!

thanks a lot for your help

Abdel Rahman Bekawi 2019-11-5

在 MATLAB Online 中打开

Here is the code from the tutorial I'm following in this link https://os.mbed.com/cookbook/Interfacing-with-Matlab

function accell()
 
TIMEOUT = 5;    %time to wait for data before aborting
XPOINTS = 50;   %number of points along x axis
 
try
    %create serial object to represent connection to mbed
    mbed = serial('COM4', ...
                  'BaudRate', 9600, ...
                  'Parity', 'none', ...
                  'DataBits', 8, ...
                  'StopBits', 1);       %change depending on mbed configuration
    
    set(mbed,'Timeout',TIMEOUT);        %adjust timeout to ensure fast response when mbed disconnected
    
    fopen(mbed);        %open serial connection
 
    position = 1;       %initialise graph variables
    time = 1;
    x = [(1:XPOINTS)' (1:XPOINTS)' (1:XPOINTS)'];
    xlabels = (1:XPOINTS);
    y = zeros(XPOINTS,3);
    % in my CASE I'm NOT having the CONDITION to be alwase TRUE as in here
    while (1)       %loop forever (or until an error occurs)
        
        values = fscanf(mbed, '%f,%f,%f');    %get values into vector
                                              %assumes data formatted as
                                              %'1,2,3'
        y(position,:) = values';    %put into y to be displayed
        
        %update position on x-axis and x-axis labels
        xlabels(position) = time;
        time = time + 1;
        if (position < XPOINTS)
            position = position + 1;
        else
            position = 1;
        end
 
        %display
        plot(x,y);
        set(gca, 'XTick', 1:XPOINTS);
        set(gca, 'XTickLabel', xlabels);
 
        drawnow;    %this is required to force the display to update before the function terminates
    end
 
    fclose(mbed);   %close connection (this should never be reached when using while(1), but included for completeness)
    
catch
    %in case of error or mbed being disconnected
    disp('Failed!');
    fclose(mbed);   %close connection to prevent COM port being lokced open
end 

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Answer 1

Murugan C 2019-11-5

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https://ww2.mathworks.cn/matlabcentral/answers/489171-serial-port-opening-problem#answer_399921

在 MATLAB Online 中打开

Hi

you should check, how many ports are open and closed using instrfind syntax in matlab.

>> instrfind
   Instrument Object Array
   Index:    Type:     Status:   Name:  
       serial    closed    Serial-COM4
       serial    closed    Serial-COM4
       serial    closed    Serial-COM1
       serial    closed    Serial-COM1
       serial    closed    Serial-COM1
       serial    closed    Serial-COM1
       serial    open      Serial-COM1

now, easily we can close all ports using fclose. and should delete that object.

   fclose(instrfind)
   delete(mbed)

correct your as like below..

try
    mbed = serial('COM1', ...
                  'BaudRate', 9600, ...
                  'Parity', 'none', ...
                  'DataBits', 8, ...
                  'StopBits', 1);       %change depending on mbed configuration
    .......
catch
    %in case of error or mbed being disconnected
    disp('Failed!');
    fclose(mbed); 
    fclose(instrfind);
    delete(mbed);
end