[Cryptech Tech] road to berlin

[Paul Selkirk]

On 04/29/2016 01:09 PM, Peter Stuge wrote:
> 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.

I think we can use I2C. We have 4 GPIO lines between the ARM and the
AVR. The CMSIS library includes an I2C module for the STM32, and it
appears from the STM32Cube examples that we can use arbitrary GPIOs. On
the AVR, there is public domain I2C master and slave code.

				paul