RE: Motion control over RS-232

["Erich Müller" <Mueller-at-eumetsat.de>]

>>> eek105-at-psu.edu 11/09/01 12:38am >>>



>>Erich asks:
>>can  EMC  be used only with step and direction over the LPT-port
>>and the dedicated hardware on the PC-bus?


>There is an example with the kaluga dro on ISA and step direction on pc-bus



>>Could it also be  interfaced over RS-232 to a motion controller with
>>proprietary protocol?

>I have been thinking about doing something like this, because I want to use
>the TI motion control dsp chips and it seems such a waste to send them an
>analog signal.  The controller in emc sends out velocity demands and expects
>position feedback.  I'm assuming that you mean one of those controllers
>(indexers) that you tell to do a move and it does it with no possibility of
>feedback.  This is problematic, and the best you could do is to strip off
>the higher level of emc and use it for your own purposes.  If the indexer
>can do coordinated moves, then this solution would be ok.  I intend to
>pretend that my d/a and encoder interface live on the serial port, and since
>I am writing the dsp code, everything will work in the current setup for
>EMC.

The feedback is needed for the servo, right? The stepper just gets steps 
and direction. No feedback. (other than reference switches or end stops)  

>>Are examples of such customisation available already?
>Unless someone is hiding something, no.
>Eric

The one I am interested in would require relative or absolute coordinates in 1, 2 
or 3 axes together with velocity specified over some serial line. A limited number 
of instructions can be stored and autarc repeat cycles of the stored instructions 
is possible. I believe the protocol used is called PAL/PC.

Erich