[Cryptech Tech] FMC Arbiter

[Fredrik Thulin]

I've started testing and have some questions/observations.

On Thursday, August 27, 2015 09:59:06 AM Fredrik Thulin wrote:
> On Thursday, August 27, 2015 12:17:05 AM Павел Шатов wrote:
...
> > Speaking of hardware issues, I got the following:
> > 
...
> > 2) Expansion connector turns out to be very sensitive to misalignment.
> > Sometimes the demo program starts getting readback mismatch errors, that
> > are all in the same bit. After I gently push the bridge board to align
> > it in parallel with the base, everything starts working fine again. I
> > also think, that such connectors are rated for a limited number of
> > mating cycles, so I try not to separate the boards without reason.

Haven't seen this yet with the board I've been testing with, luckily.

> > 3) My Novena somehow doesn't work properly, when bridge board is powered
> > from it. I removed diode D2 and added solder bridge instead to power my
> > bridge board from wall Micro-USB phone charger.
> 
> Interesting. I don't remember ever seeing any power ratings for the 5V rail
> from the Novena, but we're not consuming very much at all with the
> dev-bridge board IMO.

It seems my Novena wouldn't boot while powering the dev-bridge (fmc-test 
program already in the MCU), but I suspect some other issue than power 
consumption because my Novena won't boot with the dev-bridge attached and 
running from an external power source either (I just cut the Novena 5V input 
pin on D2).

The only way I've managed to get it up and running is by booting the Novena, 
loading the FMC bitstream you provided and *then* powering up the dev-bridge 
board.

It is as if some condition of high/low pins on the pins of the connector will 
prevent the A9 on the Novena from booting. How could that be? I thought only 
the Spartan-6 on the Novena was connected to the connector we plug into.

...
> > Demo program for STM32 keeps writing "random" stuff in FPGA, reading it 
> > back and comparing. As long as everything is fine, green LED should be 
> > on and yellow LED will blink after every batch of tests. In case of 
> > readback mismatch, red LED will be turned on.

I haven't seen the red light at all yet, but the status indicated by the 
steady green + blinking yellow is a bit unclear to me. That seems to be what 
happens both with the Novena FMC bitstream running, but also with the dev-
bridge unconnected? Just a slightly different frequency?

/Fredrik