arduino simulink com port issue

I try to connect arduino uno to matlab 2015a after installing arduino package. i test it through the command window by blinking the led and it worked. when i try to blink the led from simulink it didn't connect however i set hardware target and port number it gives error message

The call to realtime_make_rtw_hook, during the after_make hook generated the following error:
    Could not connect to specified Arduino board. 

Verify that the board is connected to your host, and that the host COM port number set in the model matches the COM port number in Windows. 

To change the host COM port number in the model, click 'Tools', click 'Run on Target Hardware', and click 'Options... In the dialog that opens, set the Host COM port number. 

To find out the COM port number in Windows, open Device Manager and open your board in the COM ports group.

The build process will terminate as a result.

Could not connect to specified Arduino board. 

Verify that the board is connected to your host, and that the host COM port number set in the model matches the COM port number in Windows. 

To change the host COM port number in the model, click 'Tools', click 'Run on Target Hardware', and click 'Options... In the dialog that opens, set the Host COM port number. 

To find out the COM port number in Windows, open Device Manager and open your board in the COM ports group.

[msh jgtu]

problem solved by changing the usb port