Re: Re: pic-servo & EMC

Andrew Werby and Andy Olney were discussing the PIC-Servo and using it
in place of the Servo To Go board for the EMC. I have been referring to
the STG board as a "dumb" IO card since it has no CPU or other chips
that do any calculations. It's just a board with an ISA bus interface to
digital-to-analog converters, encoder quadrature counters, and some
digital IO. It doesn't do any PID calculations, trajectory planning,
etc. like full-featured motion control boards (e.g., Delta Tau PMAC,
Galil DMC-1000).

The PIC-Servo sounds like it does what the STG board does, plus some
servo calculations. Some boards are in this category, where they use a
small chip for the PID calculations. This puts it in the "smarter"
category, but it still lacks the full-blown motion control of the Delta
Tau or Galil.

One easy way to use the PIC-Servo is to simply read its encoder counter
and write its DACs, bypassing any calculations. If the PIC-Servo only
has a serial interface this can get messy. I haven't done any serial
port programming in RT-Linux, but others have.

--Fred