[Cryptech Tech] Alpha board block diagram v0.001

[Basil Dolmatov]

dol@ с iPad

> 24 марта 2015 г., в 5:34, Joachim Strömbergson <joachim at secworks.se> написал(а):
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
> 
> Aloha!
> 
> Павел Шатов wrote:
>> - Give an estimate of total power consumption. How much current @
>> 12V will the board require?
> 
> Good point. I've added a note about that in the component document.
> 
> 
>> Turns out, we will not be able to have separate address and 32-bit
>> data bus. The higher part of data bus (signals EIM_D[16]..EIM_D[31])
>> are multiplexed with SPI and UART modules in iMX6Q. We can either
>> have SPI and UART, or 32-bit EIM. In this situation I suggest using
>> separate 24-bit address bus and 16-bit address bus. At 66 MHz this
>> will give us 4 times more bandwidth, than we have now.
> 
> Dang. I assume you mean 24-bit address and 16-bit data. As you say, it
> is still better than a single bus for address and data and double the
> frequency. We take what we can. I'll update the text and diagram.
> 
>> 
>> 3. USB-to-Serial Converter
>> 
>> I'm afraid, MAX3421E is not what we need. It is not a transceiver, it
>> is a Peripheral/Host controller. It does have SPI interface, but
>> this interface is used to communicate with its internal registers,
>> not to communicate with external system. I believe, what we actually
>> need is FT232R from FTDI or maybe CP2104 from SiLabs.
> 
> I've seen the following discussions re UART vs SPI. The big difference
> in general is the capacity you get. SPI being source clocked allows you
> to have 10-15 Mbps with SPI while the FTDI USB-UART chip tops out at 3
> Mbps. And the i.mx6 UARTS tops out at 4 Mbps.
> 
> This is where we should look at the use cases and what host
> communication performance we think we need for the alpha board.
> Randy and Rob, what do you think?

I am not Randy or Rob, but I think that there is NO high-bandwidth tasks in the project (at least until "kappa-board" will be started, after successful start and hitting the market of alpha- beta- and gamma-boards ;) ) and no one showed me the presence of such tasks for a year at least.

So I wonder why we constantly return to this topic and are trying to "rethink interface" without real tasks or use cases behind it. 
> 
> If we think max 3 Mbps is fine then lets use the FT232R suggested by
> Pavel. But if we think we need more we might need to rethink our host
> interface. We can:
> 
> (1) Use the USB interface in the i.mx6 directly
> 
> (2) Use something like the FT232H. More complex as it is and thus less
> trustworthy, but provides faster access.
> 
> (3) Look again at some other interface. Rob suggested raw Ethernet and
> that could be achieved in different ways: External PHY and simple 10/100
> Mbps MAC in the FPGA, external MAC+PHY as either combines or separate
> components. Or use the Ethernet-IF in the i.mx6.
> 
> 
> For the management interface, using USB-UART should be ok I believe.
> - -- 
> Med vänlig hälsning, Yours
> 
> Joachim Strömbergson - Alltid i harmonisk svängning.
>