[Freedombox-discuss] [Arm-netbook] Plug Computer

[luke.leighton]

On Sun, Oct 7, 2012 at 1:11 PM, Alexander Stephen Thomas Ross
<arm-netbook at aross.me> wrote:

> How about a plug computer for projects like FreedomBox?

 funny you should mention that :)  have we got a wiki page and/or a
mention of it on the wiki?
http://rhombus-tech.net/community_ideas/plug_computer/ no not yet -
i'll write one up after sending this.

 the task of turning an EOMA-68 CPU Card into a plug computer is...
utterly trivial.  really.  the components required are around or under
$5 in large volume.

 why?  because most of the interfaces and capabilities will already be
on the EOMA-68 Card.  a Micro-SD slot. a USB-OTG plug.  an HDMI output
will not be needed but will almost certainly be there, as a useful aid
for debugging and console display if ever needed.

 the only things needed on the plug computer's PCB would be:

 * 8 wires leading from the EOMA-68 interface to an 10/100/1000 RJ45
Ethernet socket
 * 2 wires leading from the EOMA-68 interface to an extra USB socket
 * optionally 4 wires leading from the EOMA-68 interface to an eSATA socket.
 * a way to provide 5V power from 110/240v mains.
 * an I2C EEPROM storing the EOMA-68 "devicetree" data, identifying
the I/O Board as a "plug computer" for the EOMA-68 compliant linux
kernel.

 errr... that's it.  that's all there is to it.  if you truly wanted
to save a bit more on the cost (as well as the reliability) you'd put
on a "powerable" USB Hub or other circuitry which allowed standard
"USB Chargers" to be plugged into the USB socket, as well as
mentioning in the documentation that extra power can also be provided
via any USB-OTG socket that the CPU Card itself might have.

 although... by having the main part (the CPU Card) cut out of the
device such that if the PSU fails you don't need to "get the thing
serviced" or throw away the *entire* plug computer, you just flip out
the CPU Card and put it into a new plug computer chassis...

 ... this somewhat makes the whole "use a 5V USB power supply dash
charger" idea somewhat redundant, esp. if the cost of the
EOMA-68-compliant plug computer Chassis is approaching the cost of a
charger itself.

 anyway, yes: i'll just write up that page.

l.