Re: [CAD_CAM_EDM_DRO] Re: Interface. Gauging interest.

Alan Marconett wrote:

> There are drivers to make USB look like serial, but I haven't heard of one
> for making them look like a parallel. Are they out there?

There are USB-attached devices that have a parallel port suitable for
connecting a printer under Windows. However, the Windows drivers for
them do not map them into IO space like a standard parallel port, so
they are not suitable for bit-banging in the way that CNC systems use a
standard parallel port. If someone wanted to write a VxD to connect the
IO space to the device then it could be used that way, although there is
still the issue of timing precision. Since its a virtual device writing
to the IO port with precise timing doesn't guarantee that the pins on
the output will reflect that timing.

IMO if one is going to the trouble of doing a USB attached device one
should just go ahead and make it a microcontroller and feed it the
information it needs to produce precisely timed step/direction signals.
If necessary backwards compatibility can then be provided by writing a
device driver that presents the device as a parallel port, but this
would be a secondary mode of operation. Best performance would be
provided by using the devices native command language.

> Dave,
>
> CNC dude z (?) has a free USB app and PIC project on their website that may
> be what you need to control 3 axis via USB. (No source code) ;>(
>

Cool, I'll check it out. I want to make something similar, mostly
because I like to make stuff :)

> I want a simple 4 axis USB PIC interface! Lets talk!
>

I'm interested in using an Atmel ATMega chip with integrated USB to read
commands similar (if not identical) to what the G100 reads, and then
converts those into step/direction commands. Essentially a device that
can handle 4 axis coordinated moves, but not as smart as the G100. It
would translate short 4 dimensional vectors into step and direction
commands.

I've got one other RC motor control project ahead of this one that I
need to finish, and I need to scrounge up something to read step-dir
commands (I sold my mill and HCNC board, so I don't have real hardware
any more). So I'll be doing some experiments in this direction in the
next couple of weeks.


Dave K