While connecting my Com-port using matlab, many a times(4 out of 5) I get an error
??? Error using ==> serial.fopen at 72
Port: COM21 is not available. Available ports: COM3,
COM10, COM17, COM18.
However , sometimes it gets connected and responds as expected.
Can anyone tell me whats the problem with this?
By the way , I am using this snippet to connect my microcontroller to PC through USB
s = serial('COM21'); // code to initialize the req COM i.e. COM21 for me
fopen(s);
I ran into this issue before. It turns out MATLAB doesn't really handle plug-and-play very well, as evidenced by this thread:
http://www.mathworks.com/matlabcentral/newsreader/view_thread/311133
Long story short: if you want MATLAB to detect a hardware change, you need to restart it. MATLAB seems to only look for devices when it starts up.
Related
I am using Matlab to program an experiment.
In particular, I am using these lines of code to read and send triggers to an external device:
ioObj = io64;
status = io64(ioObj);
io64(ioObj,portWriteAddress,0);
I have found the value for 'portWriteAddress by navigating to:
Device manager -> Ports -> LPT1 -> Resources. Then, in Resources there is an entry called I/O Range/ Settings with a code like 02S7 - 02SS (something like that).
Then I have converted it from Hex to Dec and put it in the line above.
THE PROBLEM IS: I am running this experiment on several different computers. Is there a way to programmatically find this range (or address) information fromMatlab?
Thank you all for your time.
Gluce
P.S.
The OS that I am using is Windows 7 (it should be soon updated to windows 10).
The computers are running either Matlab 2015b or 2016b.
I am running a code for my FPGA to collect data from accelerometer and I am able to print that to Tera Term. And I followed this tutorial to have MATLAB plot the data in real time.
I have essentially used the same code except a few changes in variable names title.
It gives me the following error.
The mathwork website has a similar question posted but there is no solution.
Open failed: Cannot connect to the COM6 port. Possible reasons are
another application is connected to the port or the port does not
exist.
Error in Untitled (line 8) fopen(s);
TIA
I am using matlab to communicate with several machines.
I am trying to connect with LCC25 (Liquid crystal retarder controller made by Thorlabs) using usb b to usb a cable.
I made a code like this.
clear all; clc;
%%
ss=serial('COM7','BaudRate',9600,'DataBits',8);
set(ss,'Parity','none');
set(ss,'Terminator','LF');
fopen(ss);
fprintf(ss,'*idn?');
aa=fscanf(ss)
fclose(ss)
Then I get "Warning : Unsuccessful read : A timeout occurred before the Terminator was reached aa=="
Is there any problem in my code?
I am also interested in buying the LCC25 and controlling it with MATLAB, so this is very interesting for me and I would love to find out whether it works...
To debug your code, I am wondering what happens when you comment out everything but:
ss=serial('COM7','BaudRate',9600,'DataBits',8);
set(ss,'Parity','none');
set(ss,'Terminator','LF');
fopen(ss);
Since then we can now if the problem is in establishing the connection itself (which you should not run every time btw!), or in trying to send a command to the device...
If the object creation is succesful, you should see something like this:
Serial Port Object : Serial-COM4
Communication Settings
Port: COM7
BaudRate: 9600
Terminator: 'LF'
Communication State
Status: closed
RecordStatus: off
Read/Write State
TransferStatus: idle
BytesAvailable: 0
ValuesReceived: 0
ValuesSent: 0
Then you can try to add run
fopen(ss)
fscanf(ss)
in a seperate file, and see what the output is. If all of this works, you can start to try sending commands using the 'fprintf' command, but make sure not to run the 'serial' and 'fopen' command every
I am wondering where you obtained the command string '*idn?', did you find this in the help file? The same for the terminator 'LF', are you sure this is the correct terminator to use for the LCC25? When reading the error message you received, I suspect the problem to be that you might need to use other terminators, such as 'CR'.
I have a Verilog code simulated and synthesized on ISE design toolkit. I've got an FPGA spartan 6 device which is to be used for the implementation. But there is a problem with the device (probably a power issue) which makes the device unavailable in any of the COM ports when I connected it to my PC. So I want to check whether my Matlab code which I made for serial communication through the device does the desired job. So I need a method to test serial communication via any of the COM ports without connecting a serial com device to the PC. Is there any such method that I can Tx Rx serial data from Matlab to COM ports? Any software or any other method would be highly appreciated :)
I found a way to test Matlab serial communication using virtual serial ports.
Download "Freeware Virtual COM Ports Emulator" from: http://freevirtualserialports.com/
I installed it in Windows 10, and it's working (as trial).
Add a pair of two serial ports:
Execute the following Matlab code sample to verify it's working:
s3 = serial('COM3','BaudRate',115200);
s4 = serial('COM4','BaudRate',115200);
fopen(s3);
fopen(s4);
fwrite(s3, uint8([1, 2, 3, 4, 5]));
%fprintf(s3, '12345');
pause(0.1);
RxBuf = fread(s4, 5)
fclose(s3);
delete(s3);
clear s3
fclose(s4);
delete(s4);
clear s4
The output is:
RxBuf =
1
2
3
4
5
Bypassing the problem "it only stays for a single test session".
There is a problem when creating a pair of virtual ports using the software, it only stays for a single test session.
I guess it's a problem with the COM port emulation software.
The following solution, is not a good practice (and not a true solution).
Declare the serial object as global, keeping the object persistent.
Create the serial object only if it's not created.
Don't delete and don't clear the serial object.
See the following code sample:
global s3 s4
if isempty(s3)
s3 = serial('COM3','BaudRate',115200);
end
if isempty(s4)
s4 = serial('COM4','BaudRate',115200);
end
fopen(s3);
fopen(s4);
fwrite(s3, uint8([1, 2, 3, 4, 5]));
pause(0.1);
RxBuf = fread(s4, 5)
fclose(s3);
%delete(s3);
%clear s3
fclose(s4);
%delete(s4);
%clear s4
You can also look for a better virtual COM port software.
As Rotem suggested, if you need to communicate via serial line between 2 program of your PC you need a virtual COM port emulator.
It seems you are running on Windows OS so I would recommend a completely free emulator (not a trial one). For Windows I use com0com Null-modem emulator (from SourceForge).
In the example below I will show how to communicate with "another" device so Matlab will not handle both side of the communication. The other device will be simulated by a simple terminal. For windows I use RealTerm: Serial/TCP Terminal (also from SourceForge).
Setup:
Execute the setup of both program with all default options. by default com0com will create a virtual pair COM3/COM4 but if these port already exist on your system the program may assign other numbers. Check the numbers before you run the example. (it will also create a CNCA0/CNCB0 pair but you can ignore this one for now).
For RealTerm, once installed (don't forget to activate the server registration at the end of the setup, it should be ticked by default though), it will look like below. Keep all default options, just set the port number and the baud rate if they need to be changed.
Test MATLAB -> Terminal
You are ready to send Ascii characters or binary values from MATLAB to your device. The animation below shows you an example of both option:
you can click on the picture to see it full size. It is running in loop so you may want to wait until it restart from the beginning.
Test Terminal -> MATLAB
Below animation shows you how to test the communication in the other way:
Don't forget to tick [CR] [LF] on RealTerm when you send Ascii characters and want to use the '%s' format specifier on MATLAB, as it needs these characters to detect the end of the string.
Note:
If you have another terminal program that you are more used too, it
will work the same.
If the RealTerm option does not suit you, or if you want to handle
both sides of communication from Matlab, then you can use the code
provided by Rotem in his first answer. Just install com0com but
ignore all the RealTerm part.
I'm trying to follow this guide on sending data from an arduino to a MATLAB program. I have every piece of code exactly matching the code in the example. However, whenever I attempt to start up the MATLAB program, I get the error message:
Error using serial/fopen (line 72) Open failed: Port: COM3 is not
available. Available ports: COM1. Use INSTRFIND to determine if other
instrument objects are connected to the requested device.
Error in Untitled8 (line 2) fopen(arduino)
Can anyone help me figure out how to get this working?
EDIT: My arduino is printing to COM3, so if I want MATLAB to hear it, it also needs to be COM3.
If I understand correctly you are using the Arduino IDE/Monitor to communicate with your Arduino on COM3. You want to have Matlab connect to the Arduino.
Since RS-232 is a point to point methology, you can only have one program/device on each end unless you add a bunch of hijinks.
When you have the Arduino IDE/Monitor open it uses the com port and other programs are denied access.
I think you need to close the Arduino monitor program to release Com port 3 and then the Matlab program should be able to open the port.