Serial Port opening problem

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Abdel Rahman Bekawi
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
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
Abdel Rahman Bekawi 2019-11-5
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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采纳的回答

Murugan C
Murugan C 2019-11-5
Hi
you should check, how many ports are open and closed using instrfind syntax in matlab.
>> instrfind
Instrument Object Array
Index: Type: Status: Name:
1 serial closed Serial-COM4
2 serial closed Serial-COM4
3 serial closed Serial-COM1
4 serial closed Serial-COM1
5 serial closed Serial-COM1
6 serial closed Serial-COM1
7 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

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