[Cryptech Tech] field upgrade

[Fredrik Thulin]

On Wednesday, May 04, 2016 06:00:38 PM Paul Selkirk wrote:
> During yesterday's meeting, Fredrik, Pavel, and I brainstormed DFU for
> the ARM.
,,,
> The ARM can only read one of the jumpers directly, so there's not a
> hardware way to distinguish an ARM upgrade from an FPGA upgrade. 

Actually, I think it would be able to.

All three of jumpers JP7, JP8 and JP9 needs to be installed for the ARM to be 
able to write the FPGA configuration memory.

What we said was this: the ARM GPIO FPGA_CFG_CTRL_ARM_ENA is connected to a 
pull-up resistor via a jumper (JP7), so if the ARM configures this GPIO as an 
input with the internal pull-down enabled, it can sense if the jumper is 
installed.

Likewise, the ARM GPIO FPGA_CFG_CTRL_FPGA_DIS is connected to a pull-down 
resistor via jumper JP8, so if the ARM enables that GPIO as an input with the 
internal pull-up enabled, it will be able to sense if the jumper is installed.

It should therefor be possible to distinguish between none, both or just one 
or the other of the three jumpers are installed.

/Fredrik
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