1.Book :
"Programming and Customizing the 8051 Microcontroller" March 1999.
If you can find this book, there is "PROG38: Ultrasonic Distance Measuring" section, full detailed.

2.
Link1:
http://www.hexamite.com/he233txrx.htm
Interfacing Ultrasonic Sensors with 8051. Schematic and Suggestions.

Link2:
http://www.8052.com/forum/read.phtml?id=94617
Another link for links to useful resources.



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