Ultrasonic ranging system controlled by PIC16F877!!!

[bing2005]

ultrasonic pic16f877

I had attached a schematic diagram. I and now try to use hi-tech c to write the source code. I dont know how to write the timer for this system. I dont know when i receive the reflected signal amd when i need to stop the timer. This schematic, i got from my friend.
Anyone please help me.
Thanks a lot!

 

[gidimiz]

Hi,

Here is a project that was writen for the MSP430, it has a schmatic and also source code in ASM. Mayby you can use that as a referance to write your code to the PIC.
**broken link removed**

Good luck.