[Arm-netbook] EOMA-68 Carrier Board Concept

[Scott Sullivan]

On 08/15/2013 04:56 PM, Christopher Thomas wrote:
> On Thu, Aug 15, 2013 at 9:20 AM, Scott Sullivan <scott at ss.org
> <mailto:scott at ss.org>> wrote:
>
>     On 08/15/2013 05:51 AM, Christopher Thomas wrote:
>
>         So, Ejectable PCMCIA, 4 Port USB Hub IC, with 2 available external
>         ports, two ports are being utilized for the ATMEGA32U4, and USB
>         Audio
>         IC.
>
>
>     I'd like to catch this now. It has been a major sin of ARM board
>     manufactures to only provide USB ports with USB connectors. The Via
>     APC boards are particularly bad for this, especial because they have
>     a mini-ITX like form factor (called Neo ATX?)[1].
>
>
> We are kind of “hamstrung” by the limitations of the 68pins. Most of the
> functionality that is being proposed on this board is duplicating
> features already present on the A20, but unfortunately, there’s no
> perfect solution to replicate ALL the functionality of a standard ATX
> Platform and still maintain an affordable and "profitable" system.
>
> Right now, I’ve done some preliminary calculations and consulting with
> manufacturers on how much a complete Turn Key system would cost, and if
> the volume of the EOMA-68 Card can get down to the more competitive
> levels predicted at the onset of the EOMA-68 project, then I feel I
> could get this down to a retail cost to the consumer at roughly $70
> (That's including the EOMA-68 CPU Card, obviously less if the CPU Card
> can be had for $15?!). Adding in $5 for an extra USB hub IC might not
> seem like much, but it could mean the difference between someone
> choosing the EOMA Platform vs the cheaper rPI or Panda Board. What you
> lose in USB, you gain in potential gains in exponential CPU advancement
> (Laws of thermodynamics not-withstanding) and the ability to upgrade,
> which is not something any current development system on the market can
> truly boast. Now, if we wanted to go with the full blown Development Kit
> Version of a fully spec’d system as described by the EOMA-68, on a full
> size ITX board, that is DEFINITELY an option, but beyond the scope of
> what I was proposing, which is an affordable, easy to produce, open
> development/experimentation/consumer-esq device.

The reason I bring this has to do with a electronics engineer colleague 
of mine. He does a variety for design with his primary buisness these 
days being audio/synthesizers ( http://www.kilpatrickaudio.com/ ).

He's expressed to me in a few times how he'd love to include a more 
powerful computer in his products. In ever case though the design of a 
PCB for RAM and SoC outweigh the value. He has considered various ARM 
dev boards over the years, but they share this same common problem. You 
can't connect to a USB port without an awkward cable exiting the case to 
connect to port on the exterior panel.

The EOMA-68 cards finally solve this common design limitation. It is now 
well within his the realm to start designing I/O board once the cards 
hit volume. In the meantime, the least I can do is impart this 
experience that it might be of great utility to have a usb port on the 
inside facing areas of the board.

I outline a few more options below.

>     Some USB ports should be brought out on the conventional 0.1"
>     headers you see on ATX motherboards (or the USB 3.0 equivalent 20pin
>     connector). This is especially important if making it ITX case
>     compatible. Cases will have front facing ports, and not including a
>     header means any user can not use their case to it's fullest.
>
>
> A potential compromise would be to have the ATMEGA32U4 as a jumper
> select-able option on the board, with the suggested headers available as
> desired, or maybe consider sacrificing some of the GPIO of the EOMA-68
> Specification and bring out the 3rd USB Host port of the A20 to the header.

So I wanted to expand on this line of thinking. Having any kind of 
programmable micro (like the ATMEGA32U4) is a great idea. But it does 
add to the cost of the board with out showing an explicit need. I'm sure 
there will be some that buy the board just for it being there. But there 
will be an equal number that will have wanted it to be a PIC. And then 
the larger majority won't care or use it.

Leaving a header, is more flexible. For those that don't want an MC they 
can leave it off and connect a front panel USB. You could then sell a 
module as an option, or other hackers can add their USB enable MC of 
choice. By leaving it off you increase options while actually reducing 
the base cost. It even gives you the option to sell a USB wifi module as 
a upgrade as well.

Second iption, don't use a header, use an internally facing USB 
receptacle. This doesn't have advantage of putting USB front panel 
connection to it, but it means you can quickly add a host of devices.

http://www.entropykey.co.uk/ - RandomNumber source
http://www.freetronics.com/products/leostick - An arduino as a USB stick.
Any USB wifi, bluetooth or 3G modems.
Another USB HUB.

A third option is to not go with the header, and instead go with a mPCI 
slot with just the USB lines attached (like in the Flying Squirrel). 
Those who want to break out the USB can use an adapter.
http://www.hwtools.net/Adapter/PM3U.html

This last options is the least flexible though.


> One of the main reasons I chose to locate the holes via the ATX
> locations was due to the increase in length. I thought, if I was going
> to be increasing the width/length to the standard ITX I/O Panel, might
> as well make it mountable in an ITX case, that's not to say it is an ITX
> computer though.
>
> I think you are spot on in that some sort of power management is
> required (Luke’s Suggestion of the AXP is a good one), as I had intended
> parts of the board to be usable even without the EOMA-68 Card
> inserted. The idea of having a hot-swappable option comes to mind, or
> programming the ATMEL chip via it's USB Bootloader.
>
>
>
>     This does mean that you'll either have to choose a Hub chip with
>     more ports, or include a second hub. Additionally, headers for front
>     panel audio, power/reset switches and LEDs should be considered as well.
>
>
> Headers for Front Panel Audio and Res/Pwr would not be hard, and are a
> good idea. Unfortunately, most of the USB3 IC's I found that had more
> than 4 Ports were about the same cost, if not more than, an additional 4
> Port Hub IC ($11-15 for a 6 port vs $4.67 for an additional 4 Port USB
> 3.0 Hub IC . ) Quantities would have to be ordered in the 1Ku to be cost
> effective.

I expected as much.

> I know I'm missing something, but I think that's the gist of it so far.
> Thank you for your input though, this is exactly the dialogue I was
> hoping to achieve.

-- 
Scott Sullivan