some first impressions

[Hal Murray]

>  - some parallel port (or similar) should be made available, for
> children to play with in physics. I remember playing with a PC
> parallel port with some simple software to turn leds on and off. When
> you are a kid, being able to send commands to projects you create is
> great (think about modern legos, but using simpler stuff like leds,
> motors, etc) : it translate the "virtual part" ie the software you
> create on the computer to the "real world" where you make leds blinks
> in sequence, or a motor move.

Where would you like to put the connector?  :)

There isn't any serial port either.  Or floppy, or CD ROM, or ...

There are USB connectors.


USB to serial adapters are readily available.  They work fine for simple 
things, but aren't great for microsecond level timings.  A quick search finds 
prices under $20.

  ntp uses one of the modem signals to catch the PPS
  (pulse per second) timing.  Many kernels have a hack
  to grab the time when a modem signal changes state.
  USB adds a lot of jitter.

You can blink LEDs by connecting them to modem control signals.


USB to printer port adapters are also available.  I've never played with one. 
 Prices are under $40.


There are also things like this with 24 GPIO lines.
  USBIO24R
  http://www.elexol.com/
  US distributor: http://www.orteches.com/  $75


  




There is also the microphone input and audio output for A/D and D/A.  I think 
the XO hardware supports a DC coupled mode.

We should work on a collection of hacks to demonstrate how they work and a 
list of which ones are known to work.












-- 
These are my opinions, not necessarily my employer's.  I hate spam.