PIC16F877A to PC serial port using RS232.

you cant connect Interrupt pin with LCD as it is used for interrupts only from IR sources. So connect LCD control pins to port A rather or any pin you like.

I wanna interface it to my pc with visual basic program. I need to add a RS232 to my circuit right? where should i connect it to? im using Microchip PIC KIT, MPLAB and ICD2

yes add RS232 circuit (MAX232) in your circuit.

Hi Matt

It seems to me you have too many components, something to avoid
where ever possible.

The 2N3904s and the LM324 are both acting as amplifiers and you don't need both.
You certainly don't need the 7476. Whatever it does should be done in software.
Removing these items will clean up your circuit and make it more reliable.

As for sharing interrupts, why bother ?
The PIC has nothing else to do so why not just connect the detectors to
two pins and continuously poll them as Ajay suggested.

>I need to add a RS232 to my circuit right? where should i connect it to?

Connect pins 25 and 26 to a MAX232 (or similar) level converter chip and connect that
to the tx and rx pins of your PC's D9 connector.

I'll leave it to you to sort out which pins,
but try this handy tutorial.
http://www.8051projects.net/serial-communication/introduction.php

Plus... you could use a smaller PIC as you don't need so many pins for the display.
A minor point, but it's better to use a name like "visitorCount" than "I" as a variable name.

Hi ExperimenterUK,

Really appreciate your advice as it really had help me alot.thanks so much. i will try to make some adjustments to my circuit and program first. later if i have any problems i will ask for help.

the polling of the IR detectors how is it done in hardware? do i just connect them by wires? or do i buy an AND gate component?

[blank]

matt you do not need opamps inbetween controller and photo-transistor, rather you can directly connect IR Receiver (photo-transistor) to controller pin or connect 2N3904 o/p to controller, which also makes polling simpler..

polling can be done the following way..
lets say normally your sensor o/p is high and when someone crosses it, o/p becomes low..

while(sensor1 && sensor2); // wait for any of sensor 1 or 2 to be crossed
if(sensor1 == 0){
     //someone crossed sensor1
}
if(sensor2 == 0){
     //someone crossed sensor2
}

this is how polling is done.

is it i should remove the LM324? what about the flip flop? do i keep it?

Just connect the collectors of the 2 transistors to 2 PIC gpio pins and remove all the rest of the components in between.
Without the comparator you would probably need to tinker a bit with the 3904's biasing to make it trigger the PIC appropriately.