Re: emc-fpga.txt

[Max Heise <mahe-at-bandstahlschnitte.de>]

Hello Keith,

> 1.  How difficult would it be to modify the EMC internals
> to support such a system as described above.

For EMC to support a new hardware interface, it is necessary to implement the
functions declared in extintf.h in an new c source file ( as an example see
extstgmot.c ). This is only some kind of dispatcher ( at least for the STG
cards ) to the real driver which implements the functions for the
internals of the new hardware ( see the stg* files as an example ). Once your
hardware is running, drop me a line and I will gladly help with writing a new
driver after my exams for the semester are over in mid/end of July.

> 2.  Would EMC be able to make any use of the FPGA-specific
> additional abilities - such as direct velocity measurement,
> sub-quarter count encoder interpolation and the direct
> numeric interpolation of splines?

Direct velocity measurement:
I don't know, ask Will or Fred, they always know the answers.

Sub-quarter count encoder interpolation: 
As long as the hardware returns the positions though the above described
software interfaces EMC should happily work with any positions feedback, so
sub-quarter count encoder interpolation is IMHO just a matter of writing a
driver for this hardware and correct setting of the input scale in your ini
file. Correct me if I am wrong. 

Direct numeric interpolation of splines:
I haven't seen anything about splines while I was looking through the rs274ngc
interpreter source, so I guess splines are not supported by the interpreter now.
In theory, limited by my somewhat restricted knowledge of EMC, adding support
for splines would involve modifying the interpreter, adding a canonical function
for splines to the posmath library and as well taking care of the usual dozens
of places you did not even know before they existed ;-) Perhaps it is
possible to have the splines split up in approximations of small tangential
connected radii. But I don't know how the motion blending will deal with
this. Does anyone have any experience with this ? 
The TkEmc GUI should be no big deal as it is only giving the NC code to the
rs274ngc interpreter and reading the interpreters status. Again correct me if I
am wrong.

Regards
Max


-- 
Max Heise <max.heise-at-gmx.net>
Student Mechatronik/Automatisierungstechnik
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