[Cryptech Tech] Alpha USB interface(s)

[Peter Stuge]

Randy Bush wrote:
> > Unless we are strongly time-constrained for the alpha
> 
> not at all.

Sarcasm isn't helpful.


Releasing is important but let's consider what the suggested change costs:

I posted an ASCII schematic indicating the simplicity of the suggested
circuit. The little Cortex-M3 might not have a symbol in EAGLE, creating
a symbol with only the 10 or so neccessary pins named takes what, two hours?

The PCB layout needs an LQFP-48 footprint, maybe another two hours.

*Very* safe estimates. I spent about an hour creating the full
footprint in the software I use.

I'm happy to contribute hand-drawn schematic, .png routing and .txt
BOM which I have used successfully.

Add another two safe hours for deleting the old circuit, drawing the
new one and routing it on board.

Add 33% margin.

That's one day for a change that brings significant technical benefits,
few if any drawbacks, and seems desirable to a couple of team members.


The toolchain used for the STM32 should work fine for the little CM3,
if not there's a build script and binaries on my workshop site.

I offered to contribute firmware. I will be visiting Stockholm in
February anyway and will gladly join Fredrik for a day if he needs
any onsite hardware assistance and/or to do firmware work.


In case it wasn't already clear, a USB CDC (USB serial port) firmware
is of course already available, so making the hardware change doesn't
mandate designing a USB protocol immediately and doesn't otherwise
close any doors for the software - it only opens new ones.


//Peter