Dear Harnam,

I think still there is some confusion :

If you are using VB front end to send commands to MCU for lighting up the output LEDS then you dont need the input port switches ( unless you want a parallel mean of inputting data ).

To send commands to MCU from the PC, the serial link is an easy option. I do hope that you know how to configure the MSComm control in VB.

Just send the byte ( consisting of the required bits )from the PC and save it into a RAM location in the MCU. Now this will be the required output image that you require to control the LEDS. The other thing that you have to decide upon, is the update interval and other mundane things like forming the input bit-pattern based on the user commands from the PC.

I can also think of another option. Retain your existing toggle switches - use the PC end for logical decoding and then enabling the outputs. For this firt read the toggle switch status into the PC via the RS232, then use that information to decide on the output pattern using a predefined logic - for example the AC must not switch ON when the main door is open and instead a warning should flash to close the door - and then output this pattern to the MCU.

The options are only limited by your imagination!!

Raghu