[Noisebridge-discuss] computer interfacing

[Dr. Jesus]

On Sat, Nov 13, 2010 at 11:38 AM,
<travis+ml-noisebridge at subspacefield.org> wrote:
> So, I've often wondered what the best way to control a computer with
> simple NO/NC inputs would be.
>
> I used to rig buttons and such to the parallel port.
>
> But computers don't have parallel ports much any more.
>
> I also used to hook them to RS-232 ports.
>
> But those are going away too.
>
> So what's left?
>
> Last I heard, several years ago, the USB drivers were still somewhat
> flaky.  Is it better now?

USB drivers for what?

> Also, HOW exactly do I hook up to USB?  With parallel it was just some
> passive circuits.  (Perhaps the answer here is "use Arduino")

FTDI chips.  Just get one of these and use the GPIO pins with the
"direct" driver:

  http://www.sparkfun.com/commerce/product_info.php?products_id=718

Many Arduinos come with this chip in addition to the Atmel MCU, but
not all of them break out the GPIO pins in a useful way.

> And, finally, how do I avoid polling loops?  (Perhaps again the
> answer is "use arduino").

Examine the FTDI drivers for how.  All modern buses support
interrupt-based operation, including nearly all parallel and serial
ports.

> And, for low-power scenarios, is there any obvious way to make a
> system that waits in a very low power mode, then wakes up on certain
> events?
>
> Things that come to mind are rigging something to soft power-on (can
> this be done on a laptop?) or Wake-on-LAN (but that requires something
> capable of sending custom ethernet packets, which itself might consume
> a fair amount of power).

Your typical PC compatible x86 platform can't be used for real-time
control if you want it to go to sleep to save power.  It takes too
long to wake up when responding to events.

At work we use industrial x86 boards for real-time control, and the
solar powered ones don't go to sleep.  For those low power
applications we use boards based on low power chips like the Vortex86.

We do have some platforms which can go to sleep, but they're not PC compatible.