[Cryptech Tech] USB interface

[Peter Stuge]

Joachim Strömbergson wrote:
> How much effort would replacing the FTDI chips and adding extra wires
> between the new chips for SPI be?

I guess the HW designer (Pavel? Fredrik?) has to say. I think it might
be a day or two for schematic and layout, but I didn't look at the layout
to see if there may be some difficult contention where new traces would go.

Regarding hardware design I'd like to place at the very top of the
wishlist to add CTS+RTS hardware flow control to the UART interface.

That adds two signals, and SPI adds another three or maybe four.

So five or six new signals would have to be routed from STM32 to each USB
interface.

The FTDI chips are fairly large, espcially considering all the support
components, they are already located near the STM32 (on opposite side)
and there isn't very much going on in the internal layers aroud there,
so this could even be real easy. I did not check what actual pins on
the STM32 we can choose from, but with six SPI blocks I hope something
will be convenient.


> > Ideally I'd like to have such an initial firmware version working already
> > by the time we must decide if we jump off the cliff. Do we know when that is?
> 
> Estimate and decision pretty much about right now. ;-)

I understand.


//Peter