Just had a request from someone for a PIC to decode the output of a rotary
encoder with quadrature output to a serial DAC.

Just wondering what would be the best way to implement the quadrature
encoding?  This application is purely for a product evaluation board so
processor choice/cost is not much of a problem.  I say this because if I
went for a mid range part (maybe a 16F84) I could use the interupt pin to
detect a rising edge on one of the quadrature signals and in the ISR read
the state of the other signal.  However, I suspect I could probably get away
with just polling the lines in a reasonanbly fast loop so I could use one of
the cheapo 16C5X devices without interupts.

Has anyone done this?  Any hints/comments?

Regards

Mike Rigby-Jones
mrjones@nortelnetworks.com