Error while Messaging with Huawei E3531 using matlab - matlab

Question

I am using Huawei E3531 model for sending message by interfacing it with matlab. But it always shows an error. Do I need to unlock my Huawei dongle?
If not, what is the actual problem? I am using the following code:
clc;
clear all;
global BytesAvail;
global A;
global B;
tx ='ATI';
tx1=char(13);
tx2=char(26);
tx3='AT+CMGS="[phone]"';
tx4= ' This is a test msg ';
tx5='AT+CMGF=1';
s = serial('COM5');
s.baudrate=9600;
fopen(s);
s.Terminator = 'CR';
fprintf(s,'%s', tx);
fprintf(s,'%s', tx1);
BytesAvail=s.BytesAvailable;
if(BytesAvail > 0), A=fread(s,BytesAvail,'char'); end
A;
sprintf('%c', A)
%%%%%%%%%%%%%%%Send SMS%%%%%%%%%%%%
fprintf(s,'%s', tx5);
fprintf(s,'%s', tx1);
fprintf(s,'%s', tx3);
fprintf(s,'%s', tx1);
fprintf(s,'%s', tx4);
fprintf(s,'%s', tx2);
BytesAvail=s.BytesAvailable;
if(BytesAvail > 0), B=fread(s,BytesAvail,'char'); end
B;
fclose(s)
The error is this
??? Error using ==> serial.fprintf at 144
An error occurred during writing.
Error in ==> message at 20
fprintf(s,'%s', tx);
>>

Answer 1

This error is caused by some virtual serial port drivers not supporting functionality equivalent to a physical serial port, and the way Matlab handles communication with the virtual serial port.
A possible solution would be to upgrade to the latest drivers (provided by the vendor of the serial port adapter).
If the error persists even with the latest drivers for the virtual serial port adapter, there is the possibility to use an alternate means of communication with serial COM ports through the VISA interface available through the Instrument Control Toolbox.
The VISA software libraries provided by Agilent/Keysight (Agilent IO Libraries) handle serial COM port communication separately from the Matlab serial port interface.
The Agilent IO Libraries can be downloaded at the following URL.
To add the virtual serial port as a VISA resource name (also refer to screenshots):
Open Agilent Connection Expert
Right click on on the desired serial port item ('COMxx') located in the 'Instrument I/O on ths PC' column, and select "Add Instrument" from the pop-up context menu.
In the following dialog box, uncheck "Auto-identify this instrument" and click OK.
Verify that the virtual serial port has been assigned a VISA resource name (for example ASRL4::INSTR)
Open MATLAB and run the following commands in the command window to show the VISA object constructor name corresponding to the VISA resource name:
visaInfo = instrhwinfo('visa', 'agilent');
visaInfo.ObjectConstructorName;
An example code for virtual serial port communication with MATLAB Instrument Control Toolbox and the VISA interface:
% --- Open and write
v = visa('agilent', 'ASRL4::INSTR');
fopen(v);
fprintf(v, 'abc');
fwrite(v, [97 98 99]);
fclose(v);
% --- Clean up
delete(v);
clear v;
Hope this helps,