Re: USB CNC (was Interface. Gauging interest.)

>
> HI John,
>
> Hopefully MACH and EMC would get "options" to use USB. And

> gain from it as well!
>
> Of course, Bert of USBCNC has already essentially ported EMC over

> using USB to his firmware (USB PIC). I don't know how "open" this
> architecture is or may become.
>
> I'd even like to try switching my STEP4 to USB. It would certainly

> interesting to try!
>
> > Thanks. So would I. Maybe after the ELS....but I'm not

> > G-Code interpreter or MACH clone. OTOH, a standardized GNU type

> > for this with a DLL library for basic motion would be useful for

> > just CNC....
>
> The DLL library approach sounds interesting. Then others could

> own Gcode or interactive "front end" DLL.
>
> Having several different levels of "USB box" at the end of the wire
> available would make putting systems together quite modular and

>
>
> >
> > Simple protocol.
> >
> > Host sends Packet of 250 x 40uS step images, Packet#, IOPort

> > etc).
> >
> > PIC sends back Packet# received, Switch Image, Error Status which

> > include Packet # and Byte # when error occurred.
> >
> > Host is held off sending more packets until response received.

> > times out and sends Info Request packet which is smaller than the

> > packets.
> >
> > Have I missed anything?
>
> Doesn't sound like it!
>
> > >
> > > You mention using the FTDI device, could the USB PIC do that
> > > as well, or
> > > would the USB core need to share interrupts with the PIC core,
> > > and would they
> > > "get in the way"?
> >
> > A quick glance at the device overview shows 1K of dual port USB

> > would imply at least two of the 250+ bytes ping pong buffers.

> > might limit this type of unit to only 4 axis as opposed to a full

> > unit. Using an external FTDI device with larger buffer offloads

> > things at the expense of a few more dollars. As in the ELS

> > is enough and when does it cost too much?
>
> A PIC-based USB-parallel board like you describe could be quite

> could easily be built into a driver/PS box. Almost like some are

> breakout boards.
>
> In fact, this USB-parallel board could be quite generic, and then

> PICs with firmware could be available. I'm wanting to try USBCNC

> CNCdudeZ PICs (although they DO use different pin assignments for

> functions...)
>
> The guys at CNCdudeZ have commented that they can compile their

> (non-coordinated) code to use different pins. That might work!

> it guys? (and if Bert at USBCNC wouldn't mind). Then we can use

> boards for more projects!
>
> > I could see a simple box that has 4 micro-stepping drivers based

> > LMD18245 devices. That would do the Sherline size mills I guess.
> > Alternatively drive the big guys with external step/dir lines.
> >
> > John Dammeyer
> >
>
> Exactly! I've just made room in my "Baby PCB Router" driver/PS box

> USB-CNC-parallel board. The output will be a DB-25 connector (also

> the back wall of the driver/PS box), so that a simple short 25-pin

> cable can "daisy-chain" into the opto-isolator board (EAS). The

> will drive 4 LMD18245 stepper driver cards (EAS), and a SSS or two.
>
> USBCNC has posted a schematic of just such a "USB-CNC-parallel"

> use with his Windoz CNC program and PIC firmware. Or you could use

> board he recommends. It looks like a PICDEM FS USB demo board

> also; although that's an expensive way to do it.
>
> http://www.usbcnc.com/
>
> OH, that does bring up an idea that I had. The PICDEM board has

> and RS-232 connectors, so like a PIC programmer I've seen, the
> "USB-CNC-parallel" board could have Rs-232 also! Does that make it

> "USB-serial-CNC-parallel" board? ;>) That WOULD be flexible!
>
> OF COURSE, I need to get the Baby PCB Router done first, and borrow

> driver/PS box from the Sherline lathe so that I can mill some

> that's the plan, anyway!
>
> Alan KM6VV
>