mantafloppy
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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 5:05 am

I was following this project mainly because of the size/form factor.

With the size increased, what gonna be the advantage over already existing plugcomputer?

Sheva, guru, dream, D2, etc...

Edit : Thx for all the answer, i'm convinced, continue your good work :)

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 5:19 am

Advantages: HDMI and video out, price, H.264 decoding (and encoding) hardware, price, power consumption, price, digital I/O header, price, ...

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 6:15 am

The main advantage is the price. Everything else that even comes close costs at least 4 times as much.

jacklang
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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 7:55 am

The main problem with the USB key size device is that there simply wasn't enough room around the edge for all the i/o people want, let alone expansion ports, test headers etc. The credit card size device looks like it will be edge space limited as well

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 12:37 pm

The USB thing was always just a prototype. Even before they got the alpha boards it was broadly advertised that the footprint goal of the final product would be credit card sized. I'm not really sure how that one took you by surprise :?

Regardless, to answer your question, there are several key differences between the various ultra small form factor PCs and the r-pi. As has been mentioned price is a huge difference, but there's a reason behind the price. R-pi is a non-profit charity. Their whole goal in designing the r-pi has been to get it into the hands of youth not only in their own country, but in developing countries as well. As such they release their product at almost cost, whereas sheevaplug costs 4 times that much just for the basic model (as well it should, they're a for profit business, there's nothing wrong with that).

Additionally, as this page shows there are a ton of i/o differences (the r-pi also comes with a lot of additional internal options beyond just JTAG, such as around 16 GPIO). It also shows that the r-pi is still the smallest form factor when it comes to size verse other options available.

So a quick summary of differences:
Size (R-pi still the smallest)
I/Os (R-pi comes with the most I/O options internally and externally)
Price (R-pi cheaper by a 4 times)
Goal (R-pi is a charity, others are all about that profit margin)
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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 4:53 pm

Is a credit card sized Raspberry Pi really that much of a deal breaker?

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 6:34 pm

I have to say, I didn't realise that the goal was credit-card sized from the outset. Certainly a lot of the initial press that R.Pi received was because of the tiny size of the prototype as evidenced by the early videos and pictures of it next to a coin.

I wouldn't say that it being credit-card sized was a deal breaker, but there are lots of tiny development boards and evaluation boards in the credit card/business card/miniPCI form factor; whereas I am aware of only one other in the usb flash/stick-of-gum form factor. The tiny form factor was one of the USPs of the R.Pi in my opinion.

One possibility might be to go to a "two PCBs stacked" design for the model-B.


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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 7:33 pm

It's down to the connectors and the cost of smaller pitch components - Gert mentioned in another thread that to get down to USB stick size, smaller components are required, and I think it was a factor of 10 difference in price. Also you mean a minimum size to get all the standard connectors on!
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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 8:01 pm

Quote from jamesh on August 22, 2011, 20:33
It's down to the connectors and the cost of smaller pitch components - Gert mentioned in another thread that to get down to USB stick size, smaller components are required, and I think it was a factor of 10 difference in price. Also you mean a minimum size to get all the standard connectors on!

Sure - to get all the components onto a single PCB. But two PCBs 90mm x 25mm stacked on top of each other have more PCB real-estate and almost twice as much perimeter than a single PCB 85mm x 55mm. So smaller components aren't required, and a stacked PCB actually makes it easier to fit all the connectors.

What does become a factor is:

a board to board connector is needed on each PCB. This adds cost and eats up some PCB real-estate.
two PCBs are naturally more expensive than one
design gets a bit more complex, requiring extra checking of trace lengths, eliminating possible interference problems and grounding problems (all small but non-negligable tasks and risks)

However there are some advantages, too. Two PCBs allows one to use more relaxed design rules on the non-CPU PCB (eg less layers, less specialised and less costly design choices) which can reduce the cost for that PCB.

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 8:27 pm

If B version will have two PCBs stacked, it will be possible to buy second PCB additionaly? When i buy A, i will can upgrade to B later simply buying second PCB (with additional ports) OR there can be another modules, like wifi, bluetooth, gps, gsm,...

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Re: What happen with USB key size(alpha prototype)?

Mon Aug 22, 2011 8:39 pm

Personally what really suprised me initially about RPi was the form factor. Just a USB size for a entire ARM11 embedded system. Now the size increased double. What happend at the beggining? didnt they give you a fixed price? now they cant continue with the initial design?

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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 8:19 am

Quote from Michael on August 22, 2011, 21:01
Quote from jamesh on August 22, 2011, 20:33
It's down to the connectors and the cost of smaller pitch components - Gert mentioned in another thread that to get down to USB stick size, smaller components are required, and I think it was a factor of 10 difference in price. Also you mean a minimum size to get all the standard connectors on!

Sure - to get all the components onto a single PCB. But two PCBs 90mm x 25mm stacked on top of each other have more PCB real-estate and almost twice as much perimeter than a single PCB 85mm x 55mm. So smaller components aren't required, and a stacked PCB actually makes it easier to fit all the connectors.

What does become a factor is:

a board to board connector is needed on each PCB. This adds cost and eats up some PCB real-estate.
two PCBs are naturally more expensive than one
design gets a bit more complex, requiring extra checking of trace lengths, eliminating possible interference problems and grounding problems (all small but non-negligable tasks and risks)
However there are some advantages, too. Two PCBs allows one to use more relaxed design rules on the non-CPU PCB (eg less layers, less specialised and less costly design choices) which can reduce the cost for that PCB.

You are talking a doubling of cost there I would think. Both in design and manufacture. The quality board to board connectors that would be needed are very expensive. It also makes the boards much less reliable.
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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 8:23 am

Quote from miauto on August 22, 2011, 21:39
Personally what really suprised me initially about RPi was the form factor. Just a USB size for a entire ARM11 embedded system. Now the size increased double. What happend at the beggining? didnt they give you a fixed price? now they cant continue with the initial design?

The initial design was a proof of principle - how small could it be made if money were no object. This then led to the idea behind the Raspberry Pi - that of a very cheap computer. Although not completely incompatible, those goals are different, so to get to the cheap cost, the size had to increase. My opinion is that the cheap goal is more important, and more useful, than the size goal.

There is a sweet spot between cheap and small, which is where the design effort is going - and the credit card size seems to be it.
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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 9:09 am

Quote from jamesh on August 23, 2011, 09:23
Quote from miauto on August 22, 2011, 21:39
Personally what really suprised me initially about RPi was the form factor. Just a USB size for a entire ARM11 embedded system. Now the size increased double. What happend at the beggining? didnt they give you a fixed price? now they cant continue with the initial design?

The initial design was a proof of principle - how small could it be made if money were no object. This then led to the idea behind the Raspberry Pi - that of a very cheap computer. Although not completely incompatible, those goals are different, so to get to the cheap cost, the size had to increase. My opinion is that the cheap goal is more important, and more useful, than the size goal.

There is a sweet spot between cheap and small, which is where the design effort is going - and the credit card size seems to be it.

Maybe i am wrong, but i am almost sure that everybody initially understood you were going to release a entire ARM11 system enclosed in a embedded size of a usb memory, not credit card size.

Just for information purposes, here you have a entire ARM9 system even smaller than a credit card size (66 x 48 mm):
http://www.embeddedartists.com.....50_oem.php

Anyway, i totally support your project.

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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 10:07 am

Quote from miauto on August 23, 2011, 10:09
Quote from jamesh on August 23, 2011, 09:23
Quote from miauto on August 22, 2011, 21:39
Personally what really suprised me initially about RPi was the form factor. Just a USB size for a entire ARM11 embedded system. Now the size increased double. What happend at the beggining? didnt they give you a fixed price? now they cant continue with the initial design?

The initial design was a proof of principle - how small could it be made if money were no object. This then led to the idea behind the Raspberry Pi - that of a very cheap computer. Although not completely incompatible, those goals are different, so to get to the cheap cost, the size had to increase. My opinion is that the cheap goal is more important, and more useful, than the size goal.

There is a sweet spot between cheap and small, which is where the design effort is going - and the credit card size seems to be it.

Maybe i am wrong, but i am almost sure that everybody initially understood you were going to release a entire ARM11 system enclosed in a embedded size of a usb memory, not credit card size.

Just for information purposes, here you have a entire ARM9 system even smaller than a credit card size (66 x 48 mm):
http://www.embeddedartists.com.....50_oem.php

Anyway, i totally support your project.

259 Euro's for the dev kit of the link you posted......bit more than $25!

The USB form factor was always a prototype. apologies if people have been misled by the size of that, but credit card size for the price and performance is still pretty good! Note also that the USB stick sized one does not have all the connectors that the final product will have, so is in fact more limited.
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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 11:05 am

I was never a fan of the usb stick design, personally. It's an arresting idea, but the hdmi-on-one-end, usb-on-the-other, flatfish shaped usb stick prototype didn't really float my boat. I'm happy with the credit card sized board. Credit card sized! :O

The usb-stick form is a nice idea for the future though, when moore's law kicks in a bit. Only it won't be a usb stick, it'll be a *hdmi* stick, drawing all needed power from the TV's hdmi port (or whatever), and communicating with peripherals/the network wirelessly...
note: I may or may not know what I'm talking about...

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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 12:29 pm

It is all a trade off, size versus price. An article posted in another thread was pretty interesting. The person being questioned stated that the size (nanometers) limit is approaching for manufacturers. So we are approaching the smallest we are going to get for a while until this barrier is breached. SoC (System on Chip) is smaller in size but taller and when there are more than three levels of stacking the loss rate for production goes way up. The SoC price is also a lot higher than the PoP design.

They are able to build the device smaller but what would the price actually be?

Gumstix are much smaller but they also need an interface board to operate. I have not seen a price but it is higher than RasPi. And its performance is much lower. In the future maybe the foundation will dig out the prototype and put it into manufacture. Right now they are headed in the direction of fulfilling the goal they set for themselves. And we, the hobby, and project market are going to benefit from it as well.
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Re: What happen with USB key size(alpha prototype)?

Tue Aug 23, 2011 12:49 pm

Quote from miauto on August 23, 2011, 10:09

Maybe i am wrong, but i am almost sure that everybody initially understood you were going to release a entire ARM11 system enclosed in a embedded size of a usb memory, not credit card size.

Actually, when I first saw the all pictures and the video of the prototype I immediately came to the main site here and instantly read "The alpha board is roughly 20% larger than the credit-card-sized final board." So I right away knew that the final product would not match the prototype (but hey, what EVER matches the prototype?)
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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 7:16 am

I too was very disappointed to see the huge size increase of the alpha boards as compared to the earlier USB stick form factor prototype. Even with a subsequent shrink to credit card size this will largely quench my interest in the Raspberry device, because I had hoped to apply it in self-contained augmented reality glasses for Android. For that, something closer to USB stick size would have been needed.

Thanks,

Peter Meijer

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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 9:27 am

Quote from jamesh on August 23, 2011, 09:19
You are talking a doubling of cost there I would think. Both in design and manufacture. The quality board to board connectors that would be needed are very expensive. It also makes the boards much less reliable.

The connectors are expensive - just under $1 in 5k bulk for each half of the Hirose 80-way connector from Mouser (although probably a lot less than that if sourced the same way as the other components).

I'm not sure I can agree with the reliability concerns either - the entire Gumstix range have been using this style of connector and don't appear to have a reliability problem with them.

It would be interesting to know just how much extra cost the two-PCB approach would encounter.

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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 12:44 pm

Please forget about the "stacked PCB's". That will not be the case. It will be a single PCB about credit card size. The "stacked PCB's" was an idea of somebody how you could make it smaller.

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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 4:46 pm

Even at credit card size, its going to be awesome :D. A credit-card sized computer is hardly large, is it?

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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 4:49 pm

to be awesome, it has to be platinum. gold as a minimum.

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Re: What happen with USB key size(alpha prototype)?

Sun Aug 28, 2011 4:58 pm

Credit card sized equals sticking RasPI, and a friend, into an EEPC and having it rattle.

Come on Gert van Loo, You dont want to invent a newer smaller version of PC104 architecture? Say a 70 to 80 pin stackable board at 5.5cm by 8.5cm?

They would only go up in cost by a factor of 20!
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