[Cryptech Tech] road to berlin

[Peter Stuge]

Paul Selkirk wrote:
> >> It appears that the AVR is programmed through a 6-pin SPI header with a
> >> usbtiny programmer, but we will need a software-based upgrade path (PC
> >> -> STM32 -> AVR).
> > 
> > That's not possible on the Alpha board since the STM32 is not
> > connected in parallel with the ISP header.
..
> On the AVR, there is public domain I2C master and slave code.

Just a technical comment on this - it might certainly be possible to
implement a "software-assisted" firmware updated method for the AVR,
where a software running on the AVR does the actual flashing.

But the hardware programming interface for the AVR is only that ISP
header, a blank AVR e.g. can not be programmed any other way, and
the same goes in case a "software-assisted" update has problems.


Another option is to use a 4-lead cable between the ISP header and
some GPIO block either for FPGA or STM32, and implement ISP
programming there - that way everything is self-hosted on the Alpha,
but updates still require human consent. I'm sure there are open ISP
programmer implementations which could be re-used.

That's all for development. For final use I too agree that it's a
feature if the AVR can't be reprogrammed so easily - actually that
probably goes for most of the programmable parts.


//Peter