Changeset 233 for branches/behrens/mfiles/COM_OpenNXTEx.m

Timestamp:

08/15/08 21:30:05 (5 years ago)

Author:

behrens

Message:

add first version of win usb lib version

Files:

• branches/behrens/mfiles/COM_OpenNXTEx.m (modified) (11 diffs)

branches/behrens/mfiles/COM_OpenNXTEx.m

@@ -182 +182 @@
     if ispc
         h.OSName    = 'Windows';
-        h.OSValue   = 2;
+        h.OSValue   = 1;
     else % no support for Mac yet...
         h.OSName    = 'Linux';
@@ -391 +391 @@
     
     if hIn.OSValue == 1
-        hOut = USB_OpenHandle_Windows(hIn, SuppressErrors);
+%         switch (hIn.ConnectionLibraryValue)
+%             case 1 % fantom library
+%                 USB_CloseHandle_Windows(h);
+%             case 2 % libusb library
+%                 USB_CloseHandle_Windows_libusb(h);
+%             otherwise
+%           end
+%         hOut = USB_OpenHandle_Windows(hIn, SuppressErrors);
+        hOut = USB_OpenHandle_Windows_libusb(hIn, false);        
     elseif hIn.OSValue == 2
         hOut = USB_OpenHandle_Linux(hIn, SuppressErrors);
@@ -428 +436 @@
     hOut.ConnectionTypeValue    = 1;
     hOut.ConnectionTypeName     = 'USB';
+
     
     
@@ -448 +457 @@
         textOut(sprintf('  - Library "fantom" already loaded.\n'));
     end%if
-        
+
+    hOut.ConnectionLibraryName = 'fantom';  % String, 'fantom' or 'libusb' / 'libusb0'
+    hOut.ConnectionLibraryValue = 1; % fantom = 1, libusb = 2
     
     
@@ -621 +632 @@
     
 %% Load libusb library (only if necessary)
+    if ~libisloaded('libusb')
+        textOut(sprintf('  - Loading library "libusb"... '));
+        try
+            % use "our" wrapper file...
+            loadlibrary('libusb', @libusb_proto)
+            textOut(sprintf('done.\n'));
+        catch 
+            textOut(sprintf('failed.\n'));
+            if ~SuppressErrors
+                error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotLoadLibraryLibusb', 'The "libusb" library could not be loaded (file "libusb" or "libusb.so"). Make sure it is installed and paths are set correctly!')
+            else
+                return
+            end%if
+        end%try
+    else
+        textOut(sprintf('  - Library "libusb" already loaded.\n'));
+    end%if
+
+
+    textOut(sprintf('  - Initializing and browsing USB busses\n'));
+
+%% Init libusb
+    textOut(sprintf('    . initializing libusb.\n'))
+    calllib('libusb', 'usb_init');
+    
+    % > - insert usb_set_debug(255) in pyusb.c right behind usb_init()
+    % > - recompile and reinstall the module
+    % > - hook up DebugView from www.sysinternals.com
+    % > - rerun your application
+    % so if we want debug mode, this needs to be uncommented!
+    %calllib('libusb', 'usb_set_debug', 255);
+
+
+    % these functions return the number of changes made to the busses and
+    % devices since last call, don't neet it...
+    textOut(sprintf('    . finding busses... '))
+    ret = calllib('libusb', 'usb_find_busses');
+    displayLibusbStatus(ret);
+    
+    textOut(sprintf('    . finding devices... '))
+    ret = calllib('libusb', 'usb_find_devices');
+    displayLibusbStatus(ret);
+
+%% Get main root bus
+    
+    textOut(sprintf('    . getting root bus object... '))
+    p = calllib('libusb', 'usb_get_busses');
+    bus = libstruct('usb_bus', p);
+    displayLibusbStatus(p);
+    
+
+    textOut(sprintf('  - Enumerating busses and devices\n'));
+
+%% Cycle through all busses and devices: enumerate...
+    foundNXT = false;
+    while ~foundNXT % for all busses
+        
+        % we want to save some debug-lines (already got too many), so we don't
+        % care what USB devices the user has. remove comment for advanced debug
+        % mode
+        %textOut(sprintf('    . current bus: %s\n', strtrim(char(bus.dirname))))
+
+        dev = libstruct('usb_device', bus.devices);
+
+        % -------------------------------------
+        while true % for all devices! sorry for endless-loop, but we break later down
+
+            % if no devs at all
+            if isempty(dev)
+                break
+            end%if
+
+
+            % we want to save some debug-lines (already got too many), so we don't
+            % care what USB devices the user has. remove comment for advanced debug
+            % mode
+            %textOut(sprintf('    . current device: %s\n', strtrim(char(dev.filename))))
+
+
+            % try a little string reading....
+
+            % THIS DOESN'T WORK UNDER LINUX MOST OF THE TIME
+            % APPARENTLY, WE CANNOT OPEN ALL PRESENT DEVICES
+            % Since we don't want to try to open a device now, we keep this
+            % working code (at least for public devices on Linux and for
+            % alle devices on Windows) commented, maybe someone else can
+            % use it to improve this function later on...
+            % It's debug-info only anyway
+
+    %        % open device to get a handle
+    %         DevHandle = calllib('libusb', 'usb_open', dev);
+    %  
+    %         % now the string stuff
+    %         buffer = blanks(255);
+    %         % we don't need a real buffer or pointer, matlab seems to do this
+    %         % for us, so we pass that buffer variable, without really needing
+    %         % it. it seems like matlab "knows" how strings get written by
+    %         % reference and returns the new value from the function. if you
+    %         % compare the matlab-returnvalues of usb_get_string_simple using
+    %         % libfunctionsview libusb, you'll find that they don't match whats
+    %         % written inside usb.h. very nice and handy, thank you matlab :-)
+    %         %pBuffer = libpointer('cstring', buffer); not needed, see above
+    %         
+    %         % now the actual call:
+    %         [bytesRead newHandleOrWhat ManufacturerName] = calllib('libusb', 'usb_get_string_simple', ...
+    %                    DevHandle, dev.descriptor.iManufacturer,  buffer, length(buffer));
+    %         % again:
+    %         [bytesRead newHandleOrWhat ProductName] = calllib('libusb', 'usb_get_string_simple', ...
+    %                    DevHandle, dev.descriptor.iProduct,  buffer, length(buffer));
+    %                
+    %         disp(sprintf('        Manufacturer: %s', ManufacturerName))
+    %         disp(sprintf('        Product: %s', ProductName))
+    %         
+    %         % close device again
+    %         ret = calllib('libusb', 'usb_close', DevHandle);
+    %         clear DevHandle %better doing it now than forgetting it later
+
+
+            % note at this point that we only try to open a device if it's one
+            % from LEGO!
+    
+            % check if it's LEGO and NXT
+            if (dev.descriptor.idVendor == ID_VENDOR_LEGO) && (dev.descriptor.idProduct == ID_PRODUCT_NXT)
+                textOut(sprintf('    . found NXT device\n'));
+
+                textOut(sprintf('    . opening device... '));
+                DevHandle = calllib('libusb', 'usb_open', dev);
+                displayLibusbStatus(DevHandle);
+
+                textOut(sprintf('    . reading serial number... '));
+                % c-syntax from documentation so we know whats going on:
+                % int usb_get_string_simple(usb_dev_handle *dev, int index, char *buf, size_t buflen);
+                buffer = blanks(255);
+                [bytesRead newHandleOrWhat SerialNo] = calllib('libusb', 'usb_get_string_simple', DevHandle, dev.descriptor.iSerialNumber,  buffer, length(buffer));
+                displayLibusbStatus(bytesRead);
+                                
+                SerialNo = strtrim(SerialNo); % just to be safe
+                textOut(sprintf('    . MAC = %s ', SerialNo))
+                
+                % is it the right one?
+                if isempty(hIn.NXTMAC) || strcmpi(hIn.NXTMAC, SerialNo)
+                    foundNXT = true;
+                    textOut(sprintf('(MAC matches, this is our desired NXT)\n'));
+                    break % search came to an end
+                else
+                    foundNXT = false;
+                    textOut(sprintf('(no match, not using this NXT)\n'));
+                    % don't forget to close the opened NXT that didnt match...
+                    textOut(sprintf('    . closing device... '));
+                    status = calllib('libusb', 'usb_close', DevHandle);
+                    displayLibusbStatus(status);
+                end%if
+                
+            end%if
+
+
+            % we are at the end of our "pointer-queue"
+            if isempty(dev.next)
+                break
+            else
+                % get next device, not that easy, but it works now \o/
+                ptr = dev.next;
+                ptr.setdatatype('usb_device');
+                dev = ptr.Value; 
+                clear ptr % to be sure, don't want to risk memory leaks
+            end%if
+            
+        end%while (for all devices)
+        % -------------------------------------
+
+        
+        % no need to scan other busses if already found
+        if foundNXT
+            break
+        end%if
+
+        % jump to next bus - same procedure as for devices, see above
+        if isempty(bus.next)
+            break
+        else
+            ptr = bus.next;
+            ptr.setdatatype('usb_bus');
+            bus = ptr.Value;
+            clear ptr
+        end%if
+        
+    end%while (for all busses)
+
+
+%% check if NXT present
+    if ~foundNXT
+        if ~SuppressErrors
+            errordlg('No NXT found on USB bus! Make sure the NXT is turned on and access rights in /dev/ are properly set. Rebooting your NXT might help!')
+            error('MATLAB:RWTHMindstormsNXT:USB:Linux:noNXTfound', 'No NXT found on USB bus! Make sure the NXT is turned on and access rights in /dev/ are properly set. Rebooting your NXT might help!')
+        else
+            % well, no NXT, exit silently
+            return
+        end%if
+    end%if
+
+
+%% NXT found, open connection
+
+    % DevHandle is now the NXT we want
+    
+    % the following commands are standard procedure for USB devices, similar usage
+    % can be found in the open source packages Python_NXT and LEGO::NXT (Perl)
+
+    % flag to remember
+    ErrorWhileOpening = false;
+    
+    % if the following fails with error -16, the NXT is probably already in
+    % use (opened in another handle!)
+    textOut(sprintf('    . setting active configuration... '));
+    % somehow this doesn't work, so we use the hardcoded configuration 1!
+    %calllib('libusb', 'usb_set_configuration', DevHandle, dev.config.bConfigurationValue);
+    ret = calllib('libusb', 'usb_set_configuration', DevHandle, LIBUSB_Configuration);
+    displayLibusbStatus(ret);
+    if (ret < 0)
+        ErrorWhileOpening = true;
+    end%if
+
+    textOut(sprintf('    . claiming interface... '));
+    % again, interface is hardcoded (compare implementations in python and
+    % perl, they do it the same way)
+    %calllib('libusb', 'usb_claim_interface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
+    ret = calllib('libusb', 'usb_claim_interface', DevHandle, LIBUSB_Interface);
+    displayLibusbStatus(ret);
+    if (ret < 0)
+        ErrorWhileOpening = true;
+    end%if
+    
+    
+    % we don't need an alternative interface, whatever that is.
+    % but from debugging experience (also with Windows), you never know
+    % when you might need this, so we keep it in here!
+    
+    % disp('    . set altinterface')
+    % %  %[int32, usb_dev_handlePtr] usb_set_altinterface(usb_dev_handlePtr, int32)
+    % ret = calllib('libusb', 'usb_set_altinterface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
+    % disp(sprintf('usb_strerror: %s', calllib('libusb', 'usb_strerror')))
+
+    % is this necessary? but found it in perl and python versions...
+    % the main point: never touch a running system
+    textOut(sprintf('    . resetting device... '));
+    ret = calllib('libusb', 'usb_reset', DevHandle);
+    displayLibusbStatus(ret);
+    if (ret < 0)
+        ErrorWhileOpening = true;
+    end%if
+    
+    % now it's time to decide:
+    if ErrorWhileOpening || isnumeric(DevHandle)
+        if ~SuppressErrors
+            errordlg('Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
+            error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotOpenNXT', 'Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
+        else
+            % again, exit silently when no success
+            return
+        end%if
+    end%if
+    
+    % finally, we're good to go!
+    hOut.Handle = DevHandle;
+    hOut.NXTMAC = SerialNo;
+
+    % and, important:
+    hOut.Connected(true);
+    
+    
+%% clean up
+
+    % is this needed? or will matlab destroy this private vars anyway after
+    % finishing this function? just to be sure with pointers...
+    clear p v bus dev newHandleOrWhat DevHandle
+
+
+end%function
+
+
+%% --- FUNCTION USB_OpenHandle_Linux
+function hOut = USB_OpenHandle_Windows_libusb(hIn, SuppressErrors)
+% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
+% Temporary USB construction site for the RWTH - Mindstorms NXT Toolbox
+%           http://www.mindstorms.rwth-aachen.de
+%
+% Alexander Behrens, 15.08.2008
+% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
+
+% Basic structure of this function:
+% Load library libusb, initialize it, get root bus object, loop through all
+% busses, for each bus loop through all devices, see if vendor and product id
+% match with lego NXT, try to open device, read serial no (which is = MAC), if it
+% matches, keep it open. then do basic USB device initialization (set config,
+% claim interface, reset device). dev should be ready then.
+
+%TODO There is still one big problem with Multi-NXT: If the first one that is
+%connected is also the first that was opened (and is now in use), the usb_open_dev
+%might fail when looping through all devs (since the dev is busy). Careful testing
+%is necessary to see wether opening an "NXT in use" fails, or if it is possible
+%and only fails when claiming its interface (I think that's the case actually, so
+%this would not be an issue after all).
+
+
+
+%% initialize etc...
+    ID_VENDOR_LEGO = 1684; % hex2dec('0694');
+    ID_PRODUCT_NXT = 2;    % hex2dec('0002');
+
+    LIBUSB_Configuration = 1;
+    LIBUSB_Interface = 0;
+    
+    
+    hOut = hIn;
+    hOut.Connected(false);
+
+    hOut.ConnectionTypeValue    = 1;
+    hOut.ConnectionTypeName     = 'USB';
+
+    
+%% Load libusb library (only if necessary)
     if ~libisloaded('libusb0')
         textOut(sprintf('  - Loading library "libusb0"... '));
@@ -630 +962 @@
             textOut(sprintf('failed.\n'));
             if ~SuppressErrors
-                error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotLoadLibraryLibusb', 'The "libusb" library could not be loaded (file "libusb" or "libusb.so"). Make sure it is installed and paths are set correctly!')
+                error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotLoadLibraryLibusb', 'The "libusb" library could not be loaded (file "libusb0.sys"). Make sure it is installed and paths are set correctly!')
             else
                 return
@@ -639 +971 @@
     end%if
 
+    hOut.ConnectionLibraryName = 'libusb0';  % String, 'fantom' or 'libusb' / 'libusb0'
+    hOut.ConnectionLibraryValue = 2; % fantom = 1, libusb = 2
 
     textOut(sprintf('  - Initializing and browsing USB busses\n'));
@@ -697 +1031 @@
             % care what USB devices the user has. remove comment for advanced debug
             % mode
-            textOut(sprintf('    . current device: %s\n', strtrim(char(dev.filename))))
+            %textOut(sprintf('    . current device: %s\n', strtrim(char(dev.filename))))
 
 
@@ -746 +1080 @@
                 textOut(sprintf('    . found NXT device\n'));
 
-%                 textOut(sprintf('    . opening device... '));
-%                 DevHandle = calllib('libusb', 'usb_open', dev);
-%                 displayLibusbStatus(DevHandle);
-% 
-%                 textOut(sprintf('    . reading serial number... '));
-%                 % c-syntax from documentation so we know whats going on:
-%                 % int usb_get_string_simple(usb_dev_handle *dev, int index, char *buf, size_t buflen);
-%                 buffer = blanks(255);
-%                 [bytesRead newHandleOrWhat SerialNo] = calllib('libusb', 'usb_get_string_simple', DevHandle, dev.descriptor.iSerialNumber,  buffer, length(buffer));
-%                 displayLibusbStatus(bytesRead);
-%                                 
-%                 SerialNo = strtrim(SerialNo); % just to be safe
-%                 textOut(sprintf('    . MAC = %s ', SerialNo))
-%                 
-%                 % is it the right one?
-%                 if isempty(hIn.NXTMAC) || strcmpi(hIn.NXTMAC, SerialNo)
-%                     foundNXT = true;
-%                     textOut(sprintf('(MAC matches, this is our desired NXT)\n'));
-%                     break % search came to an end
-%                 else
-%                     foundNXT = false;
-%                     textOut(sprintf('(no match, not using this NXT)\n'));
-%                     % don't forget to close the opened NXT that didnt match...
-%                     textOut(sprintf('    . closing device... '));
-%                     status = calllib('libusb', 'usb_close', DevHandle);
-%                     displayLibusbStatus(status);
-%                 end%if
+                textOut(sprintf('    . opening device... '));
+                DevHandle = calllib('libusb0', 'usb_open', dev);
+                displayLibusbStatus(DevHandle);
+
+                textOut(sprintf('    . reading serial number... '));
+                % c-syntax from documentation so we know whats going on:
+                % int usb_get_string_simple(usb_dev_handle *dev, int index, char *buf, size_t buflen);
+                buffer = blanks(255);
+                [bytesRead newHandleOrWhat SerialNo] = calllib('libusb0', 'usb_get_string_simple', DevHandle, dev.descriptor.iSerialNumber,  buffer, length(buffer));
+                displayLibusbStatus(bytesRead);
+                                
+                SerialNo = strtrim(SerialNo); % just to be safe
+                textOut(sprintf('    . MAC = %s ', SerialNo))
+                
+                % is it the right one?
+                if isempty(hIn.NXTMAC) || strcmpi(hIn.NXTMAC, SerialNo)
+                    foundNXT = true;
+                    textOut(sprintf('(MAC matches, this is our desired NXT)\n'));
+                    break % search came to an end
+                else
+                    foundNXT = false;
+                    textOut(sprintf('(no match, not using this NXT)\n'));
+                    % don't forget to close the opened NXT that didnt match...
+                    textOut(sprintf('    . closing device... '));
+                    status = calllib('libusb0', 'usb_close', DevHandle);
+                    displayLibusbStatus(status);
+                end%if
                 
             end%if
@@ -822 +1156 @@
 
 
-% %% NXT found, open connection
-% 
-%     % DevHandle is now the NXT we want
-%     
-%     % the following commands are standard procedure for USB devices, similar usage
-%     % can be found in the open source packages Python_NXT and LEGO::NXT (Perl)
-% 
-%     % flag to remember
-%     ErrorWhileOpening = false;
-%     
-%     % if the following fails with error -16, the NXT is probably already in
-%     % use (opened in another handle!)
-%     textOut(sprintf('    . setting active configuration... '));
-%     % somehow this doesn't work, so we use the hardcoded configuration 1!
-%     %calllib('libusb', 'usb_set_configuration', DevHandle, dev.config.bConfigurationValue);
-%     ret = calllib('libusb', 'usb_set_configuration', DevHandle, LIBUSB_Configuration);
+%% NXT found, open connection
+
+    % DevHandle is now the NXT we want
+    
+    % the following commands are standard procedure for USB devices, similar usage
+    % can be found in the open source packages Python_NXT and LEGO::NXT (Perl)
+
+    % flag to remember
+    ErrorWhileOpening = false;
+    
+    % if the following fails with error -16, the NXT is probably already in
+    % use (opened in another handle!)
+    textOut(sprintf('    . setting active configuration... '));
+    % somehow this doesn't work, so we use the hardcoded configuration 1!
+    %calllib('libusb', 'usb_set_configuration', DevHandle, dev.config.bConfigurationValue);
+    ret = calllib('libusb0', 'usb_set_configuration', DevHandle, LIBUSB_Configuration);
+    displayLibusbStatus(ret);
+    if (ret < 0)
+        ErrorWhileOpening = true;
+    end%if
+
+    textOut(sprintf('    . claiming interface... '));
+    % again, interface is hardcoded (compare implementations in python and
+    % perl, they do it the same way)
+    %calllib('libusb', 'usb_claim_interface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
+    ret = calllib('libusb0', 'usb_claim_interface', DevHandle, LIBUSB_Interface);
+    displayLibusbStatus(ret);
+    if (ret < 0)
+        ErrorWhileOpening = true;
+    end%if
+    
+    
+    % we don't need an alternative interface, whatever that is.
+    % but from debugging experience (also with Windows), you never know
+    % when you might need this, so we keep it in here!
+    
+    % disp('    . set altinterface')
+    % %  %[int32, usb_dev_handlePtr] usb_set_altinterface(usb_dev_handlePtr, int32)
+    % ret = calllib('libusb', 'usb_set_altinterface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
+    % disp(sprintf('usb_strerror: %s', calllib('libusb', 'usb_strerror')))
+
+%     % is this necessary? but found it in perl and python versions...
+%     % the main point: never touch a running system
+%     textOut(sprintf('    . resetting device... '));
+%     ret = calllib('libusb0', 'usb_reset', DevHandle);
 %     displayLibusbStatus(ret);
 %     if (ret < 0)
 %         ErrorWhileOpening = true;
 %     end%if
-% 
-%     textOut(sprintf('    . claiming interface... '));
-%     % again, interface is hardcoded (compare implementations in python and
-%     % perl, they do it the same way)
-%     %calllib('libusb', 'usb_claim_interface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
-%     ret = calllib('libusb', 'usb_claim_interface', DevHandle, LIBUSB_Interface);
-%     displayLibusbStatus(ret);
-%     if (ret < 0)
-%         ErrorWhileOpening = true;
-%     end%if
-%     
-%     
-%     % we don't need an alternative interface, whatever that is.
-%     % but from debugging experience (also with Windows), you never know
-%     % when you might need this, so we keep it in here!
-%     
-%     % disp('    . set altinterface')
-%     % %  %[int32, usb_dev_handlePtr] usb_set_altinterface(usb_dev_handlePtr, int32)
-%     % ret = calllib('libusb', 'usb_set_altinterface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
-%     % disp(sprintf('usb_strerror: %s', calllib('libusb', 'usb_strerror')))
-% 
-%     % is this necessary? but found it in perl and python versions...
-%     % the main point: never touch a running system
-%     textOut(sprintf('    . resetting device... '));
-%     ret = calllib('libusb', 'usb_reset', DevHandle);
-%     displayLibusbStatus(ret);
-%     if (ret < 0)
-%         ErrorWhileOpening = true;
-%     end%if
-%     
-%     % now it's time to decide:
-%     if ErrorWhileOpening || isnumeric(DevHandle)
-%         if ~SuppressErrors
-%             errordlg('Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
-%             error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotOpenNXT', 'Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
-%         else
-%             % again, exit silently when no success
-%             return
-%         end%if
-%     end%if
-%     
-%     % finally, we're good to go!
-%     hOut.Handle = DevHandle;
-%     hOut.NXTMAC = SerialNo;
-% 
-%     % and, important:
-%     hOut.Connected(true);
-%     
-%     
-% %% clean up
-% 
-%     % is this needed? or will matlab destroy this private vars anyway after
-%     % finishing this function? just to be sure with pointers...
-%     clear p v bus dev newHandleOrWhat DevHandle
-%% NXT found, open connection
-
-% dev should now be our NXT
-
-disp('*** Opening USB connection')
-
-disp('    . getting device handle')
-DevHandle = calllib('libusb0', 'usb_open', dev);
-if isnumeric(DevHandle)
-    ret = DevHandle;
+    
+    
+    %   // Discard any data that is left in the buffer
+    %   while (usb_bulk_read(nxt->hdl, 0x82, buf, sizeof(buf), 1) > 0)
+    %     ;
+    disp('    . discarding any data')
+    buffer = char(uint8(blanks(64)));
+    buffer = uint8(zeros(64,1));
+    ret = 1;
+    while ret > 0
+       ret = calllib('libusb0', 'usb_bulk_read', DevHandle, uint8(130), buffer, 5, 1);
+    end
+
+    %   // try to set the stream I/O feature
+    %   ret = usb_control_msg(nxt->hdl, 0x41, 0x3, 0, 0, NULL, 0, 1000);
+    %   if (ret >= 0)
+    %   {
+    %     nxt->stream_mode = 1;
+    %   }
+    disp('    . open stream modus')
+    buffer = char(uint8(blanks(64)));
+    ret = calllib('libusb0', 'usb_control_msg', DevHandle, 65, 3, 0, 0, buffer, 0, 1000);
     if ret < 0
-        disp(getLibusbErrorString(ret))
-    end%if
-end%if
-
-disp('    . reading serial number:')
-% int usb_get_string_simple(usb_dev_handle *dev, int index, char *buf, size_t buflen);
-buffer = blanks(255);
-[bytesRead newHandleOrWhat SerialNo] = calllib('libusb0', 'usb_get_string_simple', DevHandle, dev.descriptor.iSerialNumber,  buffer, length(buffer));
-disp(sprintf('      %s', SerialNo))
-
-disp('    . setting active configuration')
-%calllib(USBLIB, 'usb_set_configuration', DevHandle, dev.config.bConfigurationValue);
-ret = calllib('libusb0', 'usb_set_configuration', DevHandle, 1);
-if ret < 0
-    disp(getLibusbErrorString(ret))
-end%if
-
-disp('    . claiming interface')
-%calllib(USBLIB, 'usb_claim_interface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
-ret = calllib('libusb0', 'usb_claim_interface', DevHandle, 0);
-if ret < 0
-    disp(getLibusbErrorString(ret))
-end%if
-
-
-% disp('    . set altinterface')
-% %  %[int32, usb_dev_handlePtr] usb_set_altinterface(usb_dev_handlePtr, int32)
-% ret = calllib('libusb0', 'usb_set_altinterface', DevHandle, dev.config.interface.altsetting.bInterfaceNumber);
-% disp(sprintf('usb_strerror: %s', calllib('libusb0', 'usb_strerror')))
-% 
-
-% disp('    . resetting device')
-% ret = calllib(USBLIB, 'usb_reset', DevHandle);
-% if ret < 0
-%     disp(getLibusbErrorString(ret))
-% end%if
-
-%   // Discard any data that is left in the buffer
-%   while (usb_bulk_read(nxt->hdl, 0x82, buf, sizeof(buf), 1) > 0)
-%     ;
-disp('    . discarding any data')
-buffer = char(uint8(blanks(64)));
-buffer = uint8(zeros(64,1));
-ret = 1;
-while ret > 0
-   ret = calllib('libusb0', 'usb_bulk_read', DevHandle, uint8(130), buffer, 5, 1);
-end
-
-%   // try to set the stream I/O feature
-%   ret = usb_control_msg(nxt->hdl, 0x41, 0x3, 0, 0, NULL, 0, 1000);
-%   if (ret >= 0)
-%   {
-%     nxt->stream_mode = 1;
-%   }
-disp('    . open stream modus')
-buffer = char(uint8(blanks(64)));
-ret = calllib('libusb0', 'usb_control_msg', DevHandle, 65, 3, 0, 0, buffer, 0, 1000);
-if ret < 0
-  msg = ['Libusb error ' num2str(ret) ' while open stream mode: ' getLibusbErrorString(ret)];
-  warning('MATLAB:RWTHMindstormsNXT:USB:Linux:libusbErrorWhileOpenStreamMode', msg);
-end%if
-
-hNXT = DevHandle;
-
-% finally, we're good to go!
+      msg = ['Libusb error ' num2str(ret) ' while open stream mode: ' getLibusbErrorString(ret)];
+      warning('MATLAB:RWTHMindstormsNXT:USB:Linux:libusbErrorWhileOpenStreamMode', msg);
+    end%if
+    
+    
+    
+    % now it's time to decide:
+    if ErrorWhileOpening || isnumeric(DevHandle)
+        if ~SuppressErrors
+            errordlg('Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
+            error('MATLAB:RWTHMindstormsNXT:USB:Linux:couldNotOpenNXT', 'Something went wrong while opening the NXT device via USB (is it already open in another handle?). Please try to reboot the NXT or call COM_CloseNXT(''all'')!')
+        else
+            % again, exit silently when no success
+            return
+        end%if
+    end%if
+    
+    % finally, we're good to go!
     hOut.Handle = DevHandle;
     hOut.NXTMAC = SerialNo;
@@ -977 +1251 @@
     % and, important:
     hOut.Connected(true);
-
-
+    
+    
 %% clean up
 
-% needed? or will matlab destroy this private vars anyway after finishing
-% this function? probably...
-clear p v bus dev newHandleOrWhat 
-
-if ~isnumeric(hNXT)
-    disp('Successfully established USB connection to NXT')
-else
-    disp('Something went wrong, handle doesn''t seem valid')
-end%if
+    % is this needed? or will matlab destroy this private vars anyway after
+    % finishing this function? just to be sure with pointers...
+    clear p v bus dev newHandleOrWhat DevHandle
+
 
 end%function