Physical design

[Sam-Q]

this is probably stating the obvious but a simple solution to me for the socket problem is have two versions of the B type.

All the second version would be is the sockets are not soldered on, and instead thrown into the box that it's delivered with. Then people can just solder whatever they want in place. Probably a good idea to leave the SD card plug there though.

This way it's no extra cost of for the company (cheaper?), gives people the option to do whatever they want in putting the connectors in/leaving them off or putting wires into the board instead for remote plugs.

I say call it the Model B "developer version"

thoughts anyone?

[liz]

Quote from Sam-Q on September 10, 2011, 16:54
this is probably stating the obvious but a simple solution to me for the socket problem is have two versions of the B type.

All the second version would be is the sockets are not soldered on, and instead thrown into the box that it's delivered with. Then people can just solder whatever they want in place. Probably a good idea to leave the SD card plug there though.

This way it's no extra cost of for the company (cheaper?), gives people the option to do whatever they want in putting the connectors in/leaving them off or putting wires into the board instead for remote plugs.

I say call it the Model B "developer version"

thoughts anyone?

Have you been hanging around near my telephone?

We're almost certainly going to do this for the GPIO header - unfortunately, doing that for the other sockets doesn't actually save us any money because it means we would have to use two different processes to manufacture the board. The composite video out would be the only other candidate, and it really doesn't save you very much because it's only two wires.

[Lob0426]

The best idea I have seen so far is to mount the GPIO on the bottom of the board for expansion. And that is probably possible, when the SD is soldered on. The only problem with that is the boards height will be raised. Leaving the connector off will not, probably, save any money unless you are going to buy the connectors yourself. And then they probably would have to do a complete run of 10,000 of them to do it at the lower price. That comes down to if there are going to be 10,000 connectorless boards sold. I want at least a couple if it ever happens. For now I will have to "solder suck" if I need one without connectors, and I do. Let the solder sucking begin!

I think when Gert van Loo explains the layout decisions of the board, it will become readily apparent why we cannot have a single edge connector board. And I am already planning a way around this. I will let you know if it is successful or not. It will work, not work due to interference or I will create the "magic blue smoke". DISCLAIMER:"Some RasPi's may be harmed in this experiment".

[emercer]

+1 on the "Model C" / "Model B Developer version", I can definitely see how much flexibility replacing all the connectors with .1" spaced holes (or header strips) could add to special usage (non-Personal-Computing) cases.

[pixeltricks]

The one issue I have with the scaled down model is it may be too small. HDMI cables are not light and I currently have problems with HDMI cables pulling devices with them because the device weighs less than the cable ! I had to put velcro on my western digital live box.

[Gert van Loo]

That is why the HDMI is at the back and the mouse and keyboard at the front. Balances things out.

[Jongoleur]

Model B "Developer version" sounds more like the ZX81 build-it-yourself kit to me........

[Sam-Q]

ah I see, so two construction processes instead of two.

Also sorry if I missed it but what mounting provisions will this board have? mounting holes?

[Lob0426]

A cable tug of war going on.

Not exactly like a ZX81 kit. It was almost a bare board you soldered everything too. Too many of the RasPi components are just too small to attach yourself.

I am glad to hear you are seriously considering leaving the GPIO loose. That will solve a lot of problems for those that are going to use it. I would think stacking the RasPi on top of the expansion will work well.

Liz states there will be more info on the final boards in a couple of weeks.

[TonyD]

Quote from emercer on September 10, 2011, 18:05
+1 on the "Model C" / "Model B Developer version", I can definitely see how much flexibility replacing all the connectors with .1" spaced holes (or header strips) could add to special usage (non-Personal-Computing) cases.

+1 to developer version.

0.1" headers are great for hacking stuff to

[Sam-Q]

now back to board mounting, will the board have through holes?

The reason I ask is I have an idea that will encourage people to make their own housings up. My concept is that with the board in it's box when delivered is a dimention sheet that shows the position with (X/Y) axis of the mounting holes and the position of the sockets. This would let people like me get something CNC machined out of a block pretty easy. Or good for a company making a mould for plastic.

By the way having a TV-out socket is an excellent idea and that alone is enough for me to want one.

[choppergirl]

My Raspberry Pi physical design recommendations:

All of your connectors should be put on one side / edge of the board, NOT all around the board edge where ever its convenient from a board design perspective to bring them out. This includes the USB / keyboard / mouse connectors.

The reason is this: all those cables plugged into connectors coming out all sides of the board, take up a lot of space, and you end up with something that looks like a spider with the board in the middle as the spider body.

What you want is all those connectors to come out on one single edge, the back, so that you can take a twist tie and bundle them together and run them backwards and off the edge of a table or out of sight behind a monitor. You do not want cables sprawled all over the table. Your credit card sized computer, once you add the cables coming out in 360 degrees of directions, suddenly has no longer a credit card sized footprint.

You can have your SD slot come out either to the sides or the front, its not as important.

[liz]

Gert explains why you can't put all the connectors on one side in the hardware Q&A on the front page - it's worth a read (and it was certainly something I hadn't thought of!)

[Matthias_H]

I'm hoping for the Raspberry Pi as an affordable companion to my own USB device. For that, however, it would be good if the expansion/GPIO ports were as small as possible, since a credit card takes up more space than I have at my disposal. Have you considered a modular approach, kind of like the Gumstix Overos? Fine-pitch board-to-board connectors are widely available and not overly expensive, so they might well suited for interfacing to breakout and extension boards that could, in turn, have pretty much any size they want.

A good routing software with rubberband functionality (contracting wires to shortest possible length under given topological constraints might also help in further miniaturizing the design.

[jamesh]

Quote from Matthias_H on September 15, 2011, 05:24
I'm hoping for the Raspberry Pi as an affordable companion to my own USB device. For that, however, it would be good if the expansion/GPIO ports were as small as possible, since a credit card takes up more space than I have at my disposal. Have you considered a modular approach, kind of like the Gumstix Overos? Fine-pitch board-to-board connectors are widely available and not overly expensive, so they might well suited for interfacing to breakout and extension boards that could, in turn, have pretty much any size they want.

A good routing software with rubberband functionality (contracting wires to shortest possible length under given topological constraints might also help in further miniaturizing the design.

Modular actually means a bit more expensive I think in this case. We are taking the cheapest path approach here.

As to routing software, I believe we have some very good (expensive) stuff being used! It's actually a bit of a nightmare on this board, trying to get the size right down, and where a lot of effort is going.

[Tide]

It really would have been an advantage to have the ports on one side of the board but no use crying about spilled milk! I solved the problem on my Beagleboard by adapting the case and leading all connectors to the side and back. Looks much cleaner and at least saves the on-board ones from wear!
Just to give you some ideas:

[jamesh]

Quote from Tide on September 15, 2011, 13:36
It really would have been an advantage to have the ports on one side of the board but no use crying about spilled milk! I solved the problem on my Beagleboard by adapting the case and leading all connectors to the side and back. Looks much cleaner and at least saves the on-board ones from wear!
J

Well, depends on your definition of advantage. It's an advantage to Raspi to be < $25. That wouldn't have been possible if all the connectors were on the same side - the board would be bigger and would require more complicated routing. And, would be more expensive to send in the post (which was also a design criteria).

Since the Beagleboard design went the same way....

[Sam-Q]

I really sympathize with you guys, everyone on here is interested in a cheap micro board but if everything was added that everyone wanted it would be quadrupple the price and size. Then you virtually have the mainboard out of a netbook. As for me personally I want USB, TV out and some mounting provision so I am all good.

Everything is a compromise and I think the intial board layout is great. Off-shoots from the main design can possibly happen later, even a daughter board is an option if there's enough demand.

[Sam-Q]

Tide: assuming a power extension for the main supply you only need two sides, stick it into the corner of your box and your all set. This will let you run the USB output to a hub and have the 4 outputs on the case.

Keep in mind if this takes off (I hope so) then the availablity of new cases will come. I within my contacts can get things CNC machined out of a block of aluminium to some pretty interesting designs.

[abishur]

Tide I really like your solution! It lets anyone who just "has to have" the ports one one or two sides make it so themselves. And nice job on the case! Did you make it yourself or have a starting case that you modified?

[thesynapseuk]

I thought that the whole idea of this kind of thing was taking what you're given and then making your solution to a problem? It seems there's a lot of people moaning about the little thing they would prefer and isn't there. I'm just looking forward to learning hardcore comp-sci and seeing how far I can push this mutha.

[liz]

I very much like Tide's solution too - beautiful job. It looks really good.

I think that the "I will not buy it unless it has wheels and comes attached to a Large Hadron Collider" folk will always be with us. At least it drives discussion.

[Sam-Q]

Indeed it does, looking at Tide's enclousure sure it looks good but a lot of that space would no longer be needed. Having 1W of power usage means only a phone charger type plugpack would be needed and if necessary the shell could come off a USB hub.

I personally like the challenge of making things suit to the smallest form factor, I would probably enjoy making a case as it would be a nice change to what I usually design

[abishur]

lol Liz, I guess some people think being a non-profit company means you're supposed to be selling them for less than it costs to make them!

[stuporhero]

Quote from liz on September 15, 2011, 14:50
I think that the "I will not buy it unless it has wheels and comes attached to a Large Hadron Collider" folk will always be with us. At least it drives discussion.

This has set my imagination off. I'd love a RasPi connected to a LHC!