Here are some code snippits I wrote for the AT89C2051, which is one of Atmel's variants on the 8051 MCU.

Routine for decoding quadrature signals.

The Radio Shack SPL meter and how to make it better
How to use an SPL meter
Ampeg Tube amplifier stuff
Operating system Suck-O-Meter

Wow! What a popular page I have!