Why does TG_Connect() return -2

I am currently attempting to connect my NeuroSky Mindwave Mobile 2 to matlab, via the readRaw function provided by neurosky. It works ~1 in 20 times and most of the time returns a value of -2, meaning there were no bytes available to read from the headset. I have tried resetting the COM port, but to no avail.

function readRAW

function readRAW
%run this function to connect and plot raw EEG data
%make sure to change portnum1 to the appropriate COM port


clear all
close all

data = zeros(1,256);    %preallocate buffer

portnum1 = 3;   %COM Port #
comPortName1 = sprintf('\\\\.\\COM%d', portnum1);


% Baud rate for use with TG_Connect() and TG_SetBaudrate().
TG_BAUD_57600 =      57600;


% Data format for use with TG_Connect() and TG_SetDataFormat().
TG_STREAM_PACKETS =     0;


% Data type that can be requested from TG_GetValue().
TG_DATA_RAW =         4;

%load thinkgear dll
loadlibrary('thinkgear.dll','thinkgear.h');
fprintf('thinkgear.dll loaded\n');

%get dll version
%%dllVersion = calllib('thinkgear', 'TG_GetDriverVersion');
%%fprintf('ThinkGear DLL version: %d\n', dllVersion );


%%
% Get a connection ID handle to ThinkGear
connectionId1 = calllib('thinkgear', 'TG_GetNewConnectionId');
if ( connectionId1 < 0 )
    error( sprintf( 'ERROR: TG_GetNewConnectionId() returned %d.\n', connectionId1 ) );
end;

% Set/open stream (raw bytes) log file for connection
errCode = calllib('thinkgear', 'TG_SetStreamLog', connectionId1, 'streamLog.txt' );
if( errCode < 0 )
    error( sprintf( 'ERROR: TG_SetStreamLog() returned %d.\n', errCode ) );
end;

% Set/open data (ThinkGear values) log file for connection
errCode = calllib('thinkgear', 'TG_SetDataLog', connectionId1, 'dataLog.txt' );
if( errCode < 0 )
    error( sprintf( 'ERROR: TG_SetDataLog() returned %d.\n', errCode ) );
end;

% Attempt to connect the connection ID handle to serial port "COM3"
errCode = calllib('thinkgear', 'TG_Connect',  connectionId1,comPortName1,TG_BAUD_57600,TG_STREAM_PACKETS );
if ( errCode < 0 )
    error( sprintf( 'ERROR: TG_Connect() returned %d.\n', errCode ) );
end

fprintf( 'Connected.  Reading Packets...\n' );




%%
%record data

j = 0;
i = 0;
while (i < 10240)   %loop for 20 seconds
    if (calllib('thinkgear64','TG_ReadPackets',connectionId1,1) == 1)   %if a packet was read...
        
        if (calllib('thinkgear64','TG_GetValueStatus',connectionId1,TG_DATA_RAW) ~= 0)   %if RAW has been updated 
            j = j + 1;
            i = i + 1;
            data(j) = calllib('thinkgear64','TG_GetValue',connectionId1,TG_DATA_RAW);
        end
    end
     
    if (j == 256)
        plotRAW(data);            %plot the data, update every .5 seconds (256 points)
        j = 0;
    end
    
end





%disconnect             
calllib('thinkgear64', 'TG_FreeConnection', connectionId1 );

Error Message: 
Error using readRAW (line 57)
ERROR: TG_Connect() returned -2.

[Amer Basem]

Hello sir I'm facing the same problem Did you find the solution? Help me please Thank you

[Walter Roberson]

Error -2 is access unavailable. Some of the potential causes are listed below in https://www.mathworks.com/matlabcentral/answers/765506-why-does-tg_connect-return-2#answer_641371

Answer 1

[Walter Roberson]

No, -2 indicates that the device could not be connected to:

• the device might be in use by a different program
• the device might be in use from a previous run where the program stopped before closing
• sometimes drivers get stuck
• the device might not be turned on
• cable might be unplugged
• cable might be faulty

[Ewan Harrison]

Hi thanks for your answer. So my suspicion is that the program crashes without closing the serial port properly.

I've tried running this script to close the ports:

clear
clc
instrfind;
delete(instrfind);
clear
clc

But it hasn't worked. I'm a bit stuck for ideas now.

Again, thanks a lot for your answer

[Walter Roberson]

delete(instrfind('type', 'serial'))

would be more focused, but if what you had did not work then this will not work either.