[Arm-netbook] apologies

[joem]

On Tue, 2013-11-12 at 22:45 +0000, joem wrote:
> On Tue, Nov 12, 2013 at 7:51 PM, joem <joem at martindale-electric.co.uk> wrote:
> >> Try this :) it popped up on Google pretty quickly -->
> >> http://www.hobbytronics.co.uk/schottky-logic-level-conversion
> >
> > : awesome.  done.  added to spec.
> >
> > Same problem - access to the 3.3V power line inside the EOMA needed.
> 
> | no it is not.  TTL 3v logic is somewhere around 2v for low. a small
> |reduction (such as using another shottky diode) would be enough.
> 
> > Anyway - 3rd diagram added - modified version of Henrik's diagram for the EOMA:
> > http://www.gplsquared.com/eoma_boot/eoma_boot.html#uart_repair
> 
> | great.  1.8+3.3=5.1 so the pull-up would be to 3.23V - enough to be
> |definitely below 3.3v.
> 
> Hmmmppp... pull ups don't work like you would expect
> under certain circumstances. I'm removing the 3rd diagram from here:
> http://www.gplsquared.com/eoma_boot/eoma_boot.html#uart_repair

I don't understand what the guy is trying to say - construct and test is
one way to remove doubt.

Also I'm not sure if the second diagram i did here
http://www.gplsquared.com/eoma_boot/eoma_boot.html#uart_repair
will work under all circumstances.
If the UART TX pin defaults to a high value, the
pull up will still drive the EOMA. You would need to press <CR> a few
times to send low pulses to get the EOMA to power down.
Alternatively connect to the internal 3.3V of the CPU as in first
diagram - but sadly no access to that wire that feeds the CPU with 3.3V
through the 68 pins. (Connecting to external 3.3V is no good - it will
reproduce the said problem again.)