This is my home made metal detector ,this work is based on a russian(Eddy71) pinpointer ,the code is all mine but the idea came from is work.I added vibration and I use a faster processor ,also have included a rotine to change sensibility and detect battery low voltage.
This is the schema for the PPM signal input to microcontroller .It works very well for this project. All documentation is avaiable on this link ,dont use download manager(uncheck box). http://www.datafilehost.com/d/d6b9f5c7 The firmware is quite simple it uses 1 timer for syncronizing PPM signal and other for input capture. It does not check if data between bounds but I have no problems with this and the transmitter is very responsive .It uses PPJOY driver FMS pic 9600 Baud (0xf0+ sync) protocol. Any questions ,ask me!