Re: [Gumstix-users] Interconnecting boards

[Marshall C. <ma...@gm...>]

An FPGA will make using SPI much easier.  We have our gumstix custom
board connected to an FPGA and use SPI 3 for data transfer.  We are
connecting to sensors, not other gumstix modules though.  That will
probably be your best overall option for low power, high speed, low
chip count.  Of course it will take a bit of work for the FPGA
implementation and linux slave code.

Marshall

2011/6/21 Gerardo Richarte <ge...@di...>:
> Marshall, thanks a lot for the ideas!
>
> On 06/20/11 20:04, Marshall Crocker wrote:
>> Is Ethernet out of the question?
> well... may be, not completely though. All the Gumstix
> will be on the same board, and we need to minimize the
> chip count for a very good reason. The StageCoach design
> has one extra chip for every gumstix (MMIO to ethernet)
> and one extra chip for the whole thing (an ethernet switch).
>
> Our current idea is to use a single FPGA to interconnect
> all the Gumstix, and I thought using SPI to connect to the
> FPGA... MMIO could also be an option of course, and will
> give us higher throughput, but I think it'll make the FPGA
> design more complex, but I could be wrong... another
> issue with MMIO is that it'll consume lots of pins (data and
> address) which I could need for something else (like SPI,
> I2C, etc). But I'm not sure about this, I'd have to sit down
> to check pin by pin.
>> If that's not an option, you could always do a
>> Wifi adhoc network unless low power is a concern.
> Power is in fact a concern, and we will be very likely not
> using the WiFi enabled sticks.
>>   And of course there is always the option of connecting serial ports.
> This would be kind of lower speed than SPI, even if I push it
> up to 3.6 mbps... and then, you think I could mange to
> somehow implement any-to-any communications?
>
> oh well... it's not like I want to use an FPGA, but as I said,
> chip count is really an issue :(
>
>    thanks again!
>    gera
>
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