[Cryptech Tech] PCB prototyping machine [Was: BCP prototyping machine]

[Fredrik Thulin]

On Friday, February 27, 2015 12:05:42 PM Павел Шатов wrote:
> On 26.02.2015 0:41, Joachim Strömbergson wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA256
> > 
> > Aloha!
> > 
> > Павел Шатов wrote:
> >> Current EIM arbiter implementation takes on average 12 BCLK cycles
> >> to transfer 32 bits of data over EIM. BCLK is now 33 MHz, so the raw
> >> bandwidth is about 10 megabytes per second right now. This can be
> >> increased if necessary by changing BCLK to 66 or 133 MHz and
> >> switching to separate address/data mode from multiplexed address/data
> >> mode.
> > 
> > We seem to be thinking in the same direction. ;-) Lets crank the EIM
> > interface up a bit for the alpha board without adding too much
> > complexity on the board design. Would you say that 32-bit data @ 66 MHz
> > is a reasonable target?
> 
> Yes, this will simplify EIM arbiter a bit too. 66 MHz I/O is by all
> means possible in Spartan-6.
> 
> Speaking of Alpha Board. Joachim, what do you think about my idea to use
> CPU+RAM module from http://www.imx6rex.com/ ? If we use it, it will save
> us a great amount of time, because we will only have to develop a rather
> simple baseboard containing only power supply, an FPGA of our choice and
> mating connectors to accept this module.
> 
> The only problem is that EIM interface is not exposed on this module. It
> is not very difficult to modify it by removing unnecessary wires from it
> (HDMI, audio, UART, etc) and connection EIM pins instead. Maybe we can
> even ask authors of this module to make a customized version for us. For
> a fee maybe? They have rather user-friendly open source license.

Pavel, while I actually think your proposal is good and is very much along the 
lines of what I would personally like to have done I think the matter has been 
decided already. We are set on having someone putting together a complete PCB 
+ schematic design for the Alpha board.

I realize you (and maybe others too) are not aware of the contention we've 
seen around essentially this question already (because you haven't been with 
the project for the whole time, and we haven't had the pleasure to meet you in 
any of the face to face meetings yet) so I don't think it is unreasonable at 
all for you to try and push for this kind of modular design re-using already 
available parts.

We actually spent a lot of energy for most of December disagreeing about what 
the thing that was eventually dubbed the Alpha board would be - to the point 
of fighting about it. We healed up on the face to face meeting in early 
January, and agreed that we would go for the option of having someone do a  
complete design for us, from the ground up. I hope you can live with that.

The link you sent [1] to a page saying "this is how long it took" basically 
said it took someone without much experience 438 hours to do the iMX6 Rex 
module design. I don't know, but I think it isn't totally unreasonable to have 
an experienced professional do it in about 1/10 of that time, and I don't see 
that as a problem for this project.

Again, I personally agree with your suggestions but I value progress more than 
perfection here. I hope this e-mail helps you align with the path that we've 
chosen for now.

/Fredrik


[1] http://www.imx6rex.com/2013/11/how-long-it-took-to-design-the-imx6-rex-module-prototype/