porting new D/A boards to EMC

[Doug Fortune <pentam-at-home.com>]

Fred Proctor wrote:

> Khaweja wrote:
> > But my main question, which file contains the C code for input output for a
> > specific card, and how do i change it. I mean i do not have money to buy a
> > ServotoGo card, so i am building my own controller,
> > But i do not want to alter any of the original code of the EMC.

> The actual code that makes up these functions is board-specific. See
> emc/src/emcmot/extstgmot.c as an example. These functions map the
> external interface calls to the actual code for the Servo To Go board
> functions, in emc/src/emcmot/stg.c

In my latest round of brainstorming how to get servo's going on the cheap,
I had an idea as I came across:

http://www.bsof.com/d140prod.htm    $99  8  bit 8 channel A/D, 24 bit I/O ISA card
http://www.bsof.com/accsprod.htm      $20  DB-37 pin breakout board to connect to the
above.
                                                                        $15  DB-25 pin
breakout board for the parallel port

As you can see it has eight DAC channels at 8 bits per channel (6 usec settling
time  ie 166.6 KHz), and hence expandability up to 8 axes.    As each axis of a
homebrew  brushless motor driver circuit would have its own 20 bit up/down
counter for positional tracking,  I would use some of the bits (perferably 20,
otherwise 16)  of the 24 bit I/O to feed positional information back to EMC for a
closed loop.  Three of the remaining bits would be output as a 1-of-8 decoder to
nab the positional counter data of the desired axis.

I'd still use the parallel port,  for the Limit/spindle/coolant etc switches and relays.

Comments?

Doug Fortune
pentam-at-home.com