You have to use the RS 232 protocol to communicate between your gui and the microcontroller you can use a DB 9 connector to wire your card to the pc here some useful links for 8051 gui interfacing
If you want gui interfacing with 8051 then you can work on Visual basic (VB) . VB can help you to create graphical user interface and by using serial communication you can send data to pc from controller or viceversa. you can search for some controller projects on net that has gui interface with 8051 controller .This will definately help you.if you find any difficulty then just post ur problem here i would love to help u...........
fr the hardware part you've got to connect the serial com port on your to the serial port on 8051 using an rs232 interface.
once that is done you can test whether you're able to communicate with 8051 using MATLAB's serial commands.
then in your .m file for the gui, modify the code such that whenever you've to communicate with 8051 like while pressing a push button, matlab sends the code serially through the com port which can be received at 8051 and processed further. serial communication is the easiest way you can link matlab and 8051.
