Simtrace prototype progress

[Harald Welte]

Hi all,

Kevin and I have been making great progress today, spending about 12
hours with debugging, re-working and re-designign simtrace.

The previous malfanction seemed to be caused by attachign the Vcc from
the phone to the AD7 input of the SAM7.  Apparently the Vcc of the phone
was >= 50mV higher than the Vcc of the SAM7, and this caused the phone
(/smartcard reader) to give up as it could not raise the power line to
the level it wanted to raise it, even before switching on clock to the
card.

Aside from the one prototype, we have also received 5 units made by some
friends of K2 in china, who unfortunately used a previous gerber that
had even more bugs.  Nonetheless, three out of those 5 units have been
re-worked, and are now functional, too.

We will do a very quick 2nd prototype spin with the following changes
 * fix all the bugs as per the trac tickets
 * use the new bus switch with lower resistance
 * use a LDO with two outputs (and two enable inputs) so we can
   use a GPIO to supply the SIM card with voltage ourselves
 * add a power distribution switch with < 1Ohm Rds-on so we can
   alternatively switch through the Vcc from the phone to the SIM
 * add a resistive divider between VCC_phone and the ADC input
 * use angled jumpers so the overall unit remains flat

The gerber will be sent off tomorrow for a '3 working days' quick PCB,
the corresponding digikey order, too.

Kevin has offered to solder the next prototype.  If everything works
well, we will immediately go into production of something like 100
units to make sure they're ready before the CCC Camp (where some people
might be interested in obtaining one).

Regards,
	Harald
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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