Ah, good. I presume you already have a pic programmer so that you can program those puppies when they show up.
That schematic looks ... uh.. kind of odd to me. For example, the use of +/- 25 volts to drive the motor seems like it would be a pain in the rump. I'm not sure why they wired it up the way they did.
The use of quadrature input on the dspic , if it has that built in, should work out well. I also don't see any inputs other than the serial port, so I'm assuming it's a vector based implementation. (I'll have to look at it more closely tomorrow), and if so, you can just use the direction and step pins to increment or decrement the target location, and HOPEFULLY, if the code is well written as it stands (Again, I'll sneak a peek at it tomorrow), then it will jsut move the motor to the desired location... OH! I get the voltages now, yeah, it's an opamp in unity gain mode, so it will try to allways drive the output to equalize the inputs. So when you drive teh output, you will be using a voltage from the pic, (Pin labled as RE2) and the current limit is set by varying the voltage to the ilim pin on the op amp.
HUH... not sure if I like it, but it looks like it would work.
and 7.5 amps is a lot of current. That could turn a pretty hefty motor.
Okay, I lied, I'mlooking at it now.
... cmd_posn is the variable you want to modify to make the servo seek to a new position.
Rick