I have been developing several types of incremental encoder with PIC (in CCS and Proton IDE) and pure electronic. Starting with photo-sensors and finishing digital Hall sensors of the Allegro family.
For those wishing to enter this subject, and also for what they want to expand, I suggest these links:
Introduction to Encoders:
http://sites.google.com/site/proyectosroboticos/encoder
Pure electronic Encoder:
http://sites.google.com/site/proyect...r-por-hardware
Encoder with a PIC, with the possibility to program in CCS or Proton IDE, using RB0/INT:
http://sites.google.com/site/proyect...r-por-software
Encoder with digital Hall sensors:
http://sites.google.com/site/proyect...coder-con-hall
Best Regards.