Encoder routines.. Some of you have asked for the modifications I made to the encoder routines
to work with quadrature encoders.  
The real work of reading the encoders is done by the LS7084 from US digital
(www.usdigital.com - $3.05).  The chip takes the A and B channel inputs from
the encoder and outputs a pulse for each tick and a direction (HI or LOW).
Because the pulse is too narrow for the HB to read directly, one channel is
also connected to the HB input for the qencoder routines.
I modified the sencdr2 and sencdr4 routines to expect the input on port 2
(or 4) and the direction on port 3 (or 5).  Each "tick" is counted only on
the rising edge so the encoder2_counts variable matches the specs of the
encoder.  I also removed the encoder2_velocity variable.
I hope to do more with the LS7084 and make a complete "smart" PID sub-system
(PIC??)  Any comments or suggestions would help.
-Drew

