[Arm-netbook] GR8 based EOMA68 card

[Ismo Väänänen]

Hello,

The recent talk about de-blobbing R8 and thus also GR8 inspired me to do a
quick write up on how I see a Next Thing Co. GR8 System-In-Package chip
being used in an EOMA68 compatible card.
The latest version of the write up can be found here:
https://sites.google.com/site/oh2ftg/eoma68/eoma68-gr8

I named the project "EOMA68-GR8" because why not.

Like Vincent I'm doing this on the side and also with Altium.
I haven't done anything this complex in Altium before it's likely going to
be an interesting challenge.

GR8 has TTL/RGB LCD interface, USB2.0, I2C, SPI(SDMMC) and so on.
All the interfaces to make a compute card compatible with EOMA68 are there.
Except if I want the card to have "front facing" USB I'll need to include
some USB HUB chip like TI TUSB2046, which conveniently has no firmware
being a state machine.

I'll have to look at how the interrupts go, at AXP209 PMIC and it's routing.
And decide on if I'll layout the NAND as the talk about blobs being
required for NAND support sounds worrying. That and seeing in general if
even a half reasonable layout is possible on 4-layer FR4 to get cheaper
rates on the pcb's. At least there's no DDR RAM to route, but the TTL/RGB
fanout and length matching is gona be chore.
One more good reason to learn how the automated length matching in Altium
works.

Sourcing connectors and housings in small quantities. All that fun stuff.

If anything I have missed comes to mind please mention it, I'd rather hear
it now then when I have prototype pcb's at hand or layout nearly done.

Cheers,
Ismo Väänänen de OH2FTG alias 2ftg
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