Homebrew PCBs

Most "USB to parallel" adapters do not do what you think they do. They only
work for printers, not general parallel devices. All the CNC machines use
parallel so they can have a much dumber controller, and just diddle the
bits of the parallel port for driving the steppers, and may rely on
hardware interrupts and the very low latency of the parallel port for
timing. I'm not sure why someone hasn't come up with a generic
microcontroller based controller that does the same thing with the generic
I/O pins, and takes the gcode, or something else at a 'higher level' over
USB, as the timing over USB is not good enough to drive the motors
directly. I guess it will happen sooner or later, with the parallel port
becoming fairly scarce. Perhaps even an FTDI usb chip that has a bunch of
directly controllable I/O pins might work (like are used in some common USB
-> GPIB interfaces)

You can get PCI and PCI-e parallel port cards, and probably will be able to
for quite some time. I know some _very_ expensive devices that have direct
parallel interfaces, and rely on a 'true' hardware parallel port to work
properly.

Andrew


On Mon, Jun 10, 2013 at 4:47 PM, Jim <n6otq@...> wrote:

> **
>
>
> Well, it uses a parallel port for connectivity.  That may pose a problem
> in a few years when PC makers have utterly abandoned that interface -- the
> machine should outlast a computer.
>
> It takes G code, so as long as you can find software on W1nd0ze (or maybe
> Linux??) to support that AND a parallel interface on a replacement PC, you
> should be good to go.
>
> Since I've recently had some really bad experiences with Communist
> Chinese-supplied USB cables, I cannot blindly recommend using a parallel-to
> USB interface box/cable.
>
> I know that if I were in the market for something like this (and I kind of
> AM looking), I'd start with the software on my OS of choice first, and then
> go with a USB interface.  Finally the product differentiator would be the
> actual hardware.
>
> Basically if it won't support some flavor of *nix (I prefer a certain
> bundled BSD Unix) and USB, I won't use it.
>
> 73
> Jim N6OTQ
>
> >________________________________
> > From: Dave <dave.g4ugm@...>
> >To: Homebrew_PCBs@yahoogroups.com
> >Sent: Monday, June 10, 2013 5:29 PM
> >Subject: Re: [Homebrew_PCBs] Drilling machines, cheap Ebay routers
>
> >
> >
> >How do you compare these. I was looking at one of these:-
> >
> >
> http://www.ebay.co.uk/itm/NEW-3020-CNC-UPDATE-ROUTER-ENGRAVER-ENGRAVING-DRILLING-AND-MILLING-MACHINE-c1-/290928956948
> >
> >any idea what the difference is?
>
> [Non-text portions of this message have been removed]
>
>  
>


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