[Fab] [Noisebridge-discuss] Do we have a USB to Parallel (printer) port converter?

[miloh]

fwd'ing the discussion to the fab list --


What about expresscard slots?  Central has an adapter to parallel.  No
support for linux of course, but for the sake of comparison it's an
interesting alternative.  Does the T60 have an expresscard slot?


http://www.centralcomputers.com/commerce/catalog/product.jsp;jsessionid=9E01220BC876515377395BD22604B367?product_id=71937&czuid=1340823292437

On Tue, Jun 26, 2012 at 10:34 PM, Andy Isaacson <adi at hexapodia.org> wrote:

> On Tue, Jun 26, 2012 at 06:57:37PM -0700, Hao wrote:
> > However, I don't think Arduino-parallel converter can be used in a
> > situation that I need it to control MAXNC CNC machine in realtime, from
> > EMC2/Axis software on my laptop. Can it?
>
> You definitely cannot run MAXNC over a USB parallel port adapter.  As
> Martin says, a PCI or PCIe or even ExpressCard or PC Card (PCMCIA) would
> be more likely to work, whichever one your PC has.  Central Computer
> definitely has PCI and PCIe.
>
>


> The reason why MAXNC can't use a USB-to-parallel adapter is, you need to
> send very precisely timed signals.  USB introduces jitter and latency,
> since the USB parallel port adapter uses a whole USB packet to say "turn
> off pin 12" and similar.  (If you're *lucky* it's one packet, more
> likely it's doing a multi-round-trip conversation between your USB
> driver and the chipset in the adapter.)
>
>

Is there anything inherant to the raw speeds of usb that prevents a
parallel port adapter from being designed that actually works?
usb 2.0 is at least 10x that of the fastest parallel port standards... Are
you saying this is an impossible engineering feat?



> If you instead develop an Arduino adapter for the device, you can use
> the Arduino to provide the precise timing that you need.  Then MAXNC
> just says "hey arduino, pulse pin 1 500 times at 40 Hz, then pulse pin 2
> 30 times at 60 Hz".  The Arduino takes care of making sure the timing is
> precise.  Since it's a microcontroller it's very good at flipping bits
> at exactly the right millisecond.
>
> I'm pretty sure there are Arduino libraries for this application
> already; have you looked around at all?
>
>
Raumfahrtagenteur in Berlin replaced all the electronics in their laser
cutter and I think it's worth looking into as an alternative controller,
but I'm having trouble finding the documentation for the laser at
http://www.raumfahrtagentur.org/


> -andy
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>


-rma
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