Wireless electronic notice board using GSM

Hi,we are doing the same project(LED scrolling display using 8051)except the use of comp port,instead of that we are using GSM modem to receive the display message.we are using (7-rows,48-column ->LED matrix display)for display,AT89S52 microcontroller,GSm(sim 900) for reception of the message from a mobile phone.can u give the complete schematic of the project and code for interfacing microcontroller with GSM and LED display matrix?

The hardware for connecting to a PC or a modem is virtually , if not exactly, the same. Just check the voltage levels.
The software will be more complicated.
I suggest you build the hardware as it is, to talk to a PC.
When you have it working, look as other projects ( some on here) that talk to a GSM modem.
Finally adapt the code for your project.