> From: Kirk Wallace <kwall...@wallacecompany.com>
> Subject: Re: [Emc-developers] AVR Brain Barfing, Stepgen, USB, etc.
> To: EMC developers <emc-developers@lists.sourceforge.net>
> Message-ID: <1295129227.8603.60.camel@kw-ws>
> Content-Type: text/plain
>
> The following is what I have been working on.
>
> I would like to closely reproduce the popular FPGA signal generators,
> but move the cost down into the low cost hobby area. The cost of AVR's
> and AVR development is low enough, and caters well to open source, as
> opposed to FPGA's. The FPGA's use byte communication through a parallel
> port. I believe the common method is to send a burst of write bytes,
> then reads, which go to/from registers in the signal generator. One
> could pass plenty of bytes within each servo period. It's my preference
> to have the generator do only the high speed machine signals and let
> EMC2 do the intelligent tasks in order to preserve overall integration,
> such as with HALscope, HALmeter, and configuration files.
>
<snip>
Yeah, your recent efforts were one of the things that kept me thinking about
this and I think we're looking at this in a closely-related way if not quite
exactly.
The GRBL project (which I think is a one-man show) made an Arduino-based
machine controller (albeit using native AVR code) that not only generates
steps but actually interprets g-code with a single board. The PC is
basically just a tape drive, drip-feeding gcode. This approach seems silly
to me, kind of like pushing your car down the street rather than using the
motor, but it would seem to prove that there's enough power to run three
axes with one ATMega chip. The developer claims it works well at a 20-25KHz
step rate.
Another data point in this are the RepRap and Makerbot machines, which use
an Arduino for control of what is basically a 3-axis mill.
IMHO, there's a prize here if you can make machine latency a non-issue and
make USB a usable interface **FOR LOW-END MACHINES**. These days I have
thousands of dollars invested in all my machinery, but when I got started,
it was with a cordless drill and set of plans for a Kleinbauer Brute with a
perfboard L/R stepper driver and an ATX PSU. I got lucky and had no problem
running EMC on the first doorstop PC I had laying around. That's the kind of
user I'm thinking about....
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