f3llony
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Re: Modularity?

Sun Jul 31, 2011 3:54 pm

Hi, guys!

I see that there are a USB port on a board of Raspberry, but what about expansion ports? Some small and cheap ones, 2 or 3 of them. USB is large and space consuming, maybe there is a way to add some more non-standard ports to get ability to add some more modules which might be sold seperately from basic board? Simple as that- someone needs a WiFi- get a expansion module. Need camera? Get expansion as well. Need to add some non standard controller or something else self made? Simply connect it to that expansion port. But those, who will only need basic Raspberry will buy basic one for that exact price, and therefore You guys will be able to stay under the price limit without limiting possible ways of application for this tiny little awesome piece of art.

Sorry for my english.
:)

ShiftPlusOne
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Re: Modularity?

Sun Jul 31, 2011 7:51 pm

Seems like an arduino sort of thing. They have 'shields' which you can add to the main board to give it extra functionality.

I think a USB hub it a bit more practical. It's a popular standard and you can already get pretty much any device imaginable with linux drivers. Otherwise the R-Pi team would have to develop their own interface, shields and drivers on top of all the great work they are already doing.

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liz
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Re: Modularity?

Sun Jul 31, 2011 8:29 pm

We're bringing GPIO, I2C and SPI out to a 1.27 mm pinstrip. We also bring out MIPI CSI-2 DSI interfaces to a 1.27 mm pinstrip. I think that's a reasonable amount of non-standard IO!

USB is, as ShiftPlusOne says, practical. We're specifically looking at developing world markets, and using standard connectors minimises peripheral cost for users.
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ShiftPlusOne
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Re: Modularity?

Sun Jul 31, 2011 8:31 pm

Ah, so perhaps there will some third party modules as well.

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liz
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Re: Modularity?

Sun Jul 31, 2011 8:36 pm

Quote from ShiftPlusOne on July 31, 2011, 21:31
Ah, so perhaps there will some third party modules as well.

Yes, and that's something we really want to encourage. I hope the open source community grabs the device with both hands - there's such a lot of talent out there, and it'd mean the project would be able to accomplish a lot more than we will be able to on our own as a relatively small team.
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ShiftPlusOne
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Re: Modularity?

Sun Jul 31, 2011 8:55 pm

I think it will blow everything else out of the water. It's an expandable PC which is cheaper than an arduino. Once this comes out and there are a few projects up on hackaday, I think a lot of developers and engineers will jump on board. I just hope you guys will be able to keep up with the demand =).

Would you be open-sourcing the schematics by any chance?

f3llony
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Re: Modularity?

Sun Jul 31, 2011 9:35 pm

USB has one major drawback- it's size. It is about 15x7 mm for a hub, so it is very space consuming for this type of device. Using USB for expansion will cost a lot of space, therefore making device larger wich is a bit bad for some puproses.

But what about addapting same USB 4 pin standart but making it less space consuming? Using a different kind of receptacles, a smaller ones? It would take less space on device therefore adding possibility to engineers to connect more devices to Raspberry without tons of space consuming ports and connection will stay compatible with all the devices using USB.

Idea is like fitting a less space consuming connector on the board of Raspberry which might be connected to wires simmilar to those used to connect LCD screen in notebooks. Receptacles there is small in size therefore with lots of pins, Raspberry could addapt same approach.

I hope i made my thought clear. :)

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abishur
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Re: Modularity?

Sun Jul 31, 2011 9:49 pm

Quote from f3llony on July 31, 2011, 22:35
USB has one major drawback- it's size. It is about 15x7 mm for a hub, so it is very space consuming for this type of device. Using USB for expansion will cost a lot of space, therefore making device larger wich is a bit bad for some puproses.

But what about addapting same USB 4 pin standart but making it less space consuming? Using a different kind of receptacles, a smaller ones? It would take less space on device therefore adding possibility to engineers to connect more devices to Raspberry without tons of space consuming ports and connection will stay compatible with all the devices using USB.

Idea is like fitting a less space consuming connector on the board of Raspberry which might be connected to wires simmilar to those used to connect LCD screen in notebooks. Receptacles there is small in size therefore with lots of pins, Raspberry could addapt same approach.

I hope i made my thought clear. :)



So basically, instead of using a USB type A, use a micro-USB or mini-USB receptacle?
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f3llony
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Re: Modularity?

Sun Jul 31, 2011 10:04 pm

Basically, yes. But i meant even smaller receptacles. Soldering receptacles directly to the board from the end user's point of view is no good, because it limits the customization options very slightly and takes a lot of space even if receptacle is not used. It limits ability to fit Raspberry in small sized devices.

defiantredpill
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Re: Modularity?

Sun Jul 31, 2011 10:34 pm

micro usb would be great, but flash drives, sd card readers, cordless wifi and bluetooth adapters all need the standard sized USB.

on a side note I think its time they started making micro usb flash drives etc.

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Re: Modularity?

Sun Jul 31, 2011 10:44 pm

Too be fair, you could get adapters, or R-pi could be shipped with a micro to standard hub, but that would make it more expensive again. :/
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f3llony
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Re: Modularity?

Sun Jul 31, 2011 11:24 pm

And of course you would be able to connect to all those usb devices just by using cable with our mini connector at one end and usb hub at another one.

Lerc
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Re: Modularity?

Mon Aug 01, 2011 1:52 am

I thought that an option that would work would be a board with a single connector that brings out all IO USB, HDMI, GPIO, i2C and even power. It's not something I would recommend for the initial release but as an option later.

Having a connector to provide the current R-Pi ports would be simple, and having a more complex breakout board would allow people access to the lower level stuff.

I think the benefit of this is that I envisage the R-Pi using a lot of shared resources, such as screens and keyboards. Users may have a lot of plugging and unplugging to do. A single connector makes that process simpler. Placing the things on the other side of the connector to the R-Pi also means more expensive hardware can be effectively shared.

A common dock (for want of a better term) would be all of the standard R-Pi ports Plus 4 port USB Hub, all in a box.

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Re: Modularity?

Mon Aug 01, 2011 10:00 pm

That's a nice idea, though we'd have to work hard to keep the cost of the dock significantly below that of a RP device itself. If the dock ended up costing $15, it might just be worth putting an RP down and having the user bring their own SD card.

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Re: Modularity?

Tue Aug 02, 2011 4:31 am

To allow the option of expansion, while keeping cost and size low, I like the idea of having additional USB ports in the form of solder pads and/or pins. Otherwise having a few extra mini or micro USB ports would be nice.

f3llony
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Re: Modularity?

Tue Aug 02, 2011 6:20 am

Quote from Siguy on August 2, 2011, 05:31
To allow the option of expansion, while keeping cost and size low, I like the idea of having additional USB ports in the form of solder pads and/or pins.
I like this idea too.

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Re: Modularity?

Tue Aug 02, 2011 7:43 am

Quote from Siguy on August 2, 2011, 05:31
To allow the option of expansion, while keeping cost and size low, I like the idea of having additional USB ports in the form of solder pads and/or pins. Otherwise having a few extra mini or micro USB ports would be nice.

i like the idea as well.
i would prefer the pins..
cos´ i dont fancy to desolder cables on a tiny device if i need to.. pins are more conveniant

Michael
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Re: Modularity?

Tue Aug 02, 2011 11:53 am

The processor only provides one USB port, so either an on-board (Model-B) or off-board (Model-A) USB hub is required in order to provide additional ports. Solder pads take up the same PCB real-estate as a fitted connector so a high-density header such as Hirose is preferable where PCB real-estate is at a premium. But then you have the additional cost of the expansion board.

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Re: Modularity?

Tue Aug 02, 2011 2:47 pm

USB is large and space consuming

USB is large and space consuming? Heh... Look at a micro or mini USB-A or USB-B jack sometime. And most gear is connected nowadays via some sort of serial link, whether it's USB, FireWire, SATA, PCIe, etc. This doesn't get into that it's pretty easy to interface to most gear via USB because the support's just simply there, from cameras to printers.

Now, having said this, I think the USB line is the ONLY expansion option in the large on this device because it's a mobile media-engine chip- I don't think it's got very many GPIO lanes out of it if any. Most SoC's aren't designed with something other than a handful of USB or SDIO lines out of them, combined with a bit of HDMI/LVDS and similar support because that's all you need for the applications they're being put to. The Raspberry Pi people are re-purposing a mobile media device chip with this incarnation of their device.

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Re: Modularity?

Thu Aug 04, 2011 9:22 pm

One thing we may look into is using another chip in the SMSC LAN range (LAN9513, LAN9514) which offers more USB ports, and then bring these out to pads. There are potential impedance-management issues in doing that, but for short cables and careful wiring we may well be okay.
We have roughly 16 available GPIOs, plus I2C. We plan to offer an expansion board which buffers the built-in GPIO, and adds many more (slower) lines via an expander chip.

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