[Cryptech Tech] Novena dev-bridge board status

[Fredrik Thulin]

On Wednesday, July 08, 2015 11:00:30 PM Jacob wrote:
...
> > Real status will be reported here once I've put more (most?) of the
> > components on the board. For now, I just put on the bare minimum of
> > components plus some LEDs. I still haven't tried the real power circuitry
> > for example.
> 
> It's still exciting to watch as you go through the verification steps.

Ok, this far I have one dev-bridge board with all components mounted.

USART seems to work at 921600 bps (the ARM can read me the alphabet). Will 
verify communication is error-free next.

I'm measuring ~85 mA power consumption when powering the board through the 
USB_PWR connector. This is while busy-wait looping the ARM at 180 MHz.

The 5V rail is not exactly 5V any more. The schottky diode D2 and the inductor 
L2 (I put my finger up in the air and mounted a 47 uH there) causes a voltage 
drop of 0.8 volts. The noisy diode still gets 10.6 volts which seems to be 
enough. There are numerous ways to improve the safety margin for future 
revisions.

The panic button of all things is the only thing that doesn't seem to be 
working this far =), although I haven't tested the RTC or tamper circuitry 
beyond mounting the parts. Either I misread the datasheet, the component 
footprint didn't lend itself to hand soldering, or I need to get the ATtiny up 
and running before I can really tell.

/Fredrik
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