Q&A with our hardware team

A few days ago, Ringo, a newly minted member of our forums, posted this:

As an Electronics Engineer i’m interested with in the way the PCB has been routed and what constraints/difficulties you had during the layout process, try to fit everything on board (i’m not even refering to the updated credit card size which blows my mind how you guys can make it that small!!). I’m also interested in the power requirements and high speed digital routing (such as HDMI). Care to shed any light on this?

Most of our technically inclined readers are experienced on the software side of things, but have had less exposure to hardware engineering. Hardware’s always been a bit of an arcane art to me – I can solder things messily to breadboard, and I’ve helped Eben etch simple PCBs in our kitchen, but that’s about the limit of my knowledge, and it seems a lot of people are in a similar position. But this hardware stuff is fascinating, and Ringo’s not alone in having questions about how on earth it all fits together.

We thought the best way to structure an interview with the hardware team would be through a community Q&A. Leave questions for the guys below, and I’ll sort through for the best ones, which will be answered by Pete Lomas and Gert van Loo. Pete is MD of Norcott Technologies. He’s one of Raspberry Pi’s trustees and our Operations Director, and is responsible for the overall hardware design and implementation of the final board. Gert is a Senior Principal Engineer at Broadcom in Cambridge, and is volunteering for Raspberry Pi in his non-work time. He’s responsible for the schematic design of the alpha boards, and he’s working alongside Pete on the final board.

Please leave questions for Pete and Gert in the comments below!

205 comments

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Only one thing: Final release date?

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That’s not a hardware question! And it’s one I can answer for you – we don’t have a final date yet, but we’re hoping for the end of November.

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‘Twas the night before Christmas, when all through the house
Not a creature was stirring, not even a mouse.
The stockings were hung by the chimney with care,
In hopes that St. Nicholas soon would be there.

The geeks were nestled all snug in their beds,
While visions of Raspberry Pi danced in their heads.

…end of November? Perfect timing. :-)

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How many layers will the final board have?

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Initially there was a push for 4 layers but that is deemed too risky. So it looks like the board will be 6 layers.

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You don’t *have* to answer the short ones here as well, Gert – but thank you very much, and it’s very good of you to do so!

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Hi Guys,
A few questions then :).
1. What Schematic Entry tool are you using ?
2. Do you simulate the design for Cross Talk etc ?
3. Is there anything on the Broadcom chip or elsewhere in the design for Brown Out Detection.
4. Is there an external Watchdog or is there one internal ?
5. Will there be a need for EMC testing (suspect not but worth a query).
6. While the design is not intended to go into a ‘hazardous’ environment has there been attention paid to potection to the IO or is completely ‘naked’ ?
7. Is it possible to use different clock frequencies within the Broadcom chip so that low power applications can be implemented ?
8. If there are multiple clocks on the chip are they generated by on on board PLL or an external or by a simple divide by n counter ?
9. How many external interrupts can you wire up ?
10. If you can wire in external interrupts, what kind (edge, level) ?

There you go :).
Still think it’s an incredible project :).

Best Regards

Andre’

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I have to be terse because I expect a flood of questions:
1: For the Alpa board I used Cadence. Re-design: Ask Pete.
2: No.
3: No.
4: None.
5: Tricky: experimental boards are often exempt. But some countries you can’t import without certificate. So we will test them once we have a case.
6: All main connectors have ESD protection. (USB/HDMI etc.) On the expansion your on our own!
7: The HW has capabilities but it depends on the SW to enable them. So that is up to the drivers.
8: We have PLLs. Same as before SW drivers!
9/10: Each GPIO can interrupt, high/low/rise/fall/change.

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Excellent, thank you for the reply :)

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My questions:

1) How much power will the end versions consume? Will they both fit under 1000mA? This is going to be a factor if we’re running the Pi off batteries (ideally, the less power consumption = longer run time).

2) How about a battery pack for the RPi? Maybe call it the RaspBattery?

3) Any future model ideas? Like a revision of the version A that ditches a USB port for intergrated WiFi/BlueTooth (like the pandaboard’s nifty WiFi/BT module)?

4) Can we overclock that CPU? (Getting at least 1Ghz would be great!)

…that’s my questions for now.

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1: We are still looking at the power circuit. Expect a more detailed post in about a week!
2: There are no plans from the Raspberry team.
3: No, too busy with A and B and then probably a plug-in board then 4 layer PCB then…
4: I am the hardware engineer responsible for the final product qualification. As such I am not allowed to believe in over clocking.

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Would it be possible to run the RasPi from solar power via some batteries?

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Absolutely – we don’t anticipate any difficulty in that scenario.

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Baking a mean flapjack aside, does that mean you heavily influenced the name Raspberry PIE?? seriously, power consumption is important if one were trying to incorporate the RP in to an existing keyboard. With space to put batteries and a few solar cells (cannablised garden lights from the pound shops) you have a enviromentally geared portable computer.
Aesthetically a bit naff but this function over form, because you can :)

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Considering the Pi is sold as a ‘bare’ circuit board, how durable is it over time? Is it something that we would want to put in a case as soon as possible? Should we be extremely cautious about electrostatic shock and so on?

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I cannot give official results, but I carry my proto home wrapped (sometimes) in an anti static bad in a rucksack. I take no anti static precautions once it’s on my desk.

It’s still working.

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Yes, you have to be a bit more careful then with ‘packaged’ computers. Do not switch it on when you put it on top of your keys nor drop anything metal on it when it is on. (Or off…) You will NOT get a static shock from it. All main connectors have ESD (Electro Static Discharge) protection: USB, HDMI, TV_out etc. But not on anything else. So do not rub you cat and then see if you can draw a spark from the GPIO connector. That is likely to convert your PI to a door stop. (http://dilbert.com/strips/comic/1999-07-02/)

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What were the original parameters you were looking for in the final product and how close did you come to them. Processor speed? Processor type? GPU performance? Memory size? PCB size? Available connectors? Etc.

Where do you start, choosing the SoC?

Richard

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Well, the Raspi charity is somewhat biased (in a good way) in that one of the founders works for Broadcom as an architect for the Videocore range of GPU’s.

This means under the hood access to a lot of information about the SoC, and also, critically, a good price normally only available in very large quantity purchases. This means that there isn’t a similar performing chip even close pricewise.

Broadcom, because of the connection, have also been very generous in time and engineering expertise. Without this connection I doubt the Raspberry Pi would have been possible.

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Broadcom does not appear to provide IC chip data , pinouts or sell the chips to anyone but very large large users ( millions of chips ? ) .
So I would guess that one of the founders of RaspBerry Pi swings a lot of influence at Broadcom. Will this person remain anonymous ?
Is Raspberry Pi ( RbPi ) operating under a non-disclosure agreement ( NDA ) ? If RbPi does not answer the NDA question… then I presume they are restricted by an NDA .

If there is no NDA …… then let us see IC pinouts , IC register descriptions , ……..

Also PCB schematic and layout .

Best 99guspuppet

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One of the founder does work for Broadcom – Eben Upton (I also work for Broadcom). This has been stated many time on this site, he has never been anonymous. I don’t know about a non-disclosure agreement – perhaps. Not that it makes much difference.

As has also been stated before, you really have no need for access to register descriptions (and in fact for the GPU it doesn’t work that way, so are irrelevant). The Arm is a standard Arm11 – you can look up the datasheet for that from Arm (The processor part number is on this site somewhere)

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Hello again Gus. I’ve got a funny feeling I’ve discussed this with you before. I recommend you go back to the thread on our forums about the BCM2835, where our relationship with Broadcom is explained in full about a million times. I’ve typed this stuff so often now that I’m starting to worry that my hands are going through the motions as I sleep.

To précis yet again: one of our founders, Eben Upton, has always been absolutely transparent about the fact that he’s a multimedia architect at Broadcom. (There are six founders; only one works at Broadcom. You can confirm this by looking up our charities commission entry.) Raspberry Pi has been a personal charitable project of his, not connected to his work at Broadcom, for about four years now. (I should know – I’m married to him.) Some of our friends at Broadcom have helped with the development of the board on a volunteer basis outside their working hours. This hasn’t come about for any conspiratorial reasons; it just happens that when you work alongside good engineers for a number of years, make friends with them and have a worthwhile project to work on outside school-time, some of those good engineers will volunteer to help you out. Other friends from other engineering companies are also working on Raspberry Pi – none of us makes any money from this. We are all volunteering because we think it is a good thing to do.

Broadcom has no further involvement than selling chips to us. We were able to get our foot in the door to discuss buying chips in much smaller numbers than they usually sell (you’re right about millions of chips) because Eben works there and was able to get access to the right people, who were right on side once we had explained the goals of the charity. Ours is a customer/supplier relationship.

This means, of course, that we at the Raspberry Pi Foundation have no more ability to open up the multimedia core than any other of Broadcom’s customers. We do have an NDA, like every single one of their other customers. This is totally common business practice; I would have been very surprised if we didn’t.

We would have liked to be able to have a completely open platform, but until the open-source community tapes out a chip, it looks like that will be impossible. (If you have the expertise, please get working on one. I would love the open-source community to put their money where their mouths are on this one; it’d be good for all of us.) We are contractually bound to use the SoC in a way approved by the people who manufacture it. We needed to use a mobile SoC for reasons of power, size, multimedia capability and compute power. We didn’t just look at Broadcom chips – we looked at TI, Nvidia and other SoCs as well, but it happens that the one we are using is the least expensive (by a factor of about 2) in its field; it was also very helpful that many on the engineering team were very familiar with it. No other SoC manufacturers are opening their multimedia cores either, so the choice of another chip wouldn’t have made a difference.

I hope you understand the reasons we are making this board. I will be the first to admit that while we think the goals of open are admirable and desirable, they have not been at the top of our list. We are making it to democratise computing – to make cheap and powerful computers available to schools and to the developing world. There’s a philosophical and price tension here; we simply couldn’t reach the goal of making a cheap, tiny, powerful computer and reach your goal of a completely open platform with the same device. If you find this is a personal problem for you, you’re very welcome not to buy one, but I’d really appreciate it if you could try to think of how this works from the position of a bunch of people who have put years of work into trying to make the world a better place, have secured borrowing on their houses to make sure everything goes smoothly, and are having to deal with strange insinuations from people we’ve never met on the internet on an almost daily basis as a result. Do you leave messages like this for the makers of mobile phones or set top boxes? We are in the same position vis a vis the SoC as they are.

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Bravo

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Extremely comprehensive answer, thanks for the insights. As a rather old fart, I remember waiting for the BBC TV computer program coming on back in times of old, recording the audio code at the end to load up onto my computer on my cassette player. Those were the days of the BBC Micro A and B. This project provokes the same feelings in me then as that project did back then and I am full of admiration and gratitude for what you guys have set out to achieve.

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The above provided me with lots of information I was not aware of before.

……..Yes…. I leave similar messages directed at Netgear about their so-called open source routers. [ http://www.myopenrouter.com/ ]… Netgear and I disagree about what open source means. The routers in question are based on Broadcom chips and are under NDAs and leave lots of very juicy information unreleased.

So I love/hate Broadcom …. they make exceptional chips and they have lots of secrets. And they don’t sell chips in small quantities.

By the way …… I would never suggest getting the government involved in any of this …. I love free enterprise and personal freedom.

99guspuppet

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Will the built in audio jack work as a line in as well as an output?

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I assume you want to connect it to a line-in.
Not directly The signal strength is too high. You should use some resistors to reduce the amplitude.

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Thanks for the reply, I’d be looking connect a line level source to it, to record then output over the network for transcoding/streaming purposes.

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I am afraid that is not what I meant. It is an output. You can connect it *to* a line-in. You can *not* use it as an input. The Raspi has no sound input.

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Is there somewhere a A/D input one can solder to? Even less that 16 bits?

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You could always use a USB audio input device (there are hundreds of cheap ones that will work perfectly well) instead of mucking about with a soldering iron. As long as it’s supported under Linux, you shouldn’t have any problem, I should imagine.

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I’ve been talking to a local school and they’re incredibly interested in extracurricular teaching (via an after school club) for students interested in learning more about “Real I.T.” with the Raspberry Pi.

The biggest (hardware related) question they have is how easy is it to interface with external interfaces, such as a breadboard containing simple logic/lights/motors etc. The possibility of teaching students how to program external interfaces is very appealing to them as it not only teaches software, but basic hardware skills.

Is there, or will there be, some simple interface board which would help facilitate this?

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It is very likely that we will make one or more expansion cards. Just don’t ask me when they will be available.

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The RP device as it stands has a USB requiring connection to a HUB for mice/keyboards and any other USB devices. Now RPF may not have the simple interface board yet and may or may not have them in the future, however there are USB interface boards already out there, you just need to ensure the drivers (if need) will be compatable with the Linux operating system provided. Maplins is one such place http://www.maplin.co.uk/usb-experiment-interface-board-42857 is typical, but not for Linux, although it comes with a dll so you could write your own software. However the interface board above is a Vellerman one, the same as noted here http://libk8055.sourceforge.net/ which does provide Linux drivers, a bit of searching will normally find a solution. With a cost of around £30, the board would add a lot of functionality to the £25 RP and still be within the finacial pockets of many. I do personally think however a simpler 8 I/O board could be made even cheaper.

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… I think that Rashberry pi will connect straight to an arduino – so then you have a great tinkering system. I’ve used Python on a PC and Aduino’s together and its awesome!!

PS Rashberry pi and Reprap — now there’s a thought

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Now, funnily enough, I got talking to the RepRap guys at the Transfer Summit a couple of weeks ago – and they also had that thought. We think it’d be a lovely pairing too (and I’m trying to clear some space in the lab for a RepRap to play with once we’re a little less busy).

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Not a question – just want to tell you I’m a huge fan of Raspberry Pi and now that I read you are talking with RepRap guys…! That’s just plain incredible! RepPi FTW!

Good luck to you good people.

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Also: Raspberry Pi and Sense (from the Open University)
It’s a Freeduino & a custom version of MIT Scratch. The Scratch component ought to run on the Raspberry Pi.

http://sense.open.ac.uk/

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Is there a clock on the RasPi? Is it battery-backed?

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I can answer that one – no, there isn’t. (They’re surprisingly expensive when you’re in a position where every penny counts – ditto for cells to power them.)

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Um I don’t think, a quartz for realtime clock is that expensive.
As for my Dockstar, adding realtime clock to the board was only a few pence. http://gsg-elektronik.de/?id=92

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Add that few pence to the cost of a lithium cell and multiply those costs by a million units, and you start to see what our problem is. You can add a clock if you’re hardware-handy anyway if you really need one.

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What will the lack of a clock mean for the end user?

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That, just like in the 80’s, you have type in the date and time. (Or write a utility which auto reads it from an ip address).

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@daniel: if connected to the internet it can resync on startup. Other than that time will just “stop” when unplugged i think.

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Just so you know, it’s not actually all that necessary. Some modern distros can automatically fetch and update the proper time (and probably also date) for you from a time server. You’ll just be with a wrong time setting while booting.

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Yeah – that’s what’s happening with implementation of Debian we’ve been using in demos.

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Will the schematics & GERBER files be available for the PCB before launch so we enthusiasts can set to work on our add-on boards?

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Not sure about full schematics but we will certainly be able to explain the expansion connector pin-out form factor placement etc.

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I am interested in the bus architecture of this system and what the theoretical attached capacity is for this SoC. How much bandwidth is available to attached devices? Are the device types hardwired? For example, I’m sure the pinout on the Broadcom has dedicated connections for HDMI and the SDHC. Is the USB integrated as well? Is there a general bus to which a variety of third market chips could be attached? I’ve heard that the ethernet is connected through the USB bus. Is this necessary, or just cheaper? Is there a recommended primer somewhere that would explain ARM system buses and how they differ from the x86 architectures?

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There is no external bus. So you have to do with what is there and we can’t tell you exactly until we know which pins we can all bring out. If you look at the forum you will find that we have GPIO, SPI, I2C, UART, etc. With no dedicated bus it is not very useful to talk about Bandwidth.The Broadcom chip has USB which comes out on model A and goes to an on-board HUB(which has two USBs and Ethernet) on model B. Sorry again no system bus external ARM nor x86.

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Too much people (I am one of that pool) “ask to much” (“why dont you add this”?, “why dont you add that”?) to this thin devece that always is underlined to be “bare metal” as they planned since initial plan and so it is not possible to change/add now new features tha are out of scope.
This device is actracting our interests, and i will buy at least one model B for test, but I hope that in future RaspberryPI Team collet these several requests and will plan a “board@steroids” with some bigger features ( ie: 4usb and/or 2NIC and/or 512RAM) as people asks to have. No metter to pay more money if we get more stuffs.

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One can design add on-boards to the core main RbPi board……. which is nice. Please don’t add a bunch of bells and whistles that others can add with daughter boards. If the Broadcom chip does it natively ( camera support ? ) …. great. Otherwise , furrgetit.

Probably no one outside of RbPi will be able to layout a competing main board since the BroadCom chip ( or it’s datasheet ) is unlikely to available to anyone but large corporations.
99guspuppet

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Will there be a way of disabling some hardware parts for a lower power mode, such as, If I’m using a Wireless USB Dongle (or 3G USB Modem), can I disable the Ethernet module in order to get a lower overall power consumption!

I’m asking this because I already had some Linux Embedded boards that I used for several situations where I could use the board via Ethernet connection, or Wifi, or 3G Modem, and all powered by a external battery where I needed to squeeze as much juice as I could! (unfortunately this boards didn’t allowed such operation).

And what about the GPU, is it possible to disable it temporarily and run a special Linux OS without X … my idea is the same, could use the Raspberry PI for a remoter weather data collector, and I would not need the GPU for that, so disabling it for a lower power profile!

Just asking if it is possible, I imagine that this would be something complicated to manage! Same thought here, Raspi is already perfect for me, just trying to get it the most portable as possible (where all the other hardware failed, power hungry when connected to batteries)

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The GPU already has a pretty aggressive power save mode – all automatic. So, if you are not doing anything using the GPU, most of it will be turned off. I think, if there is nothing connected to HDMI, then that block is also turned off, but not sure.

Don’t know about the Arm or the Ethernet controller. (Get a model A as well – no ethernet on that one!!)

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WOW, delighted to know about the GPU aggressive power save mode!

Yup, I’ll get both model A and B just in case ;).

Regards, you guys rock!

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If you really want to save power, forget 3G modem, use wifi wisely or have a look on zigbee or bluetooth low energy. Switch of X, unneeded services, slow down cpu (easy from bootloader) and pray for power save mode on all devices.

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Given that Sophie Wilson of BBC Micro and Arm fame now works at Broadcom, have you had any advice from her on this project?

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You have to ask Eben. I only do hardware.

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Hi

I’d love to use this to replace my media PC for movie’s etc.
Have you tested with any USB sound cards at all to get full some surround sound loving going on?

Matt

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No. We can’t test all the different devices. We hope for lots of equipment to be tested by the Raspberry Pi community once we get the boards out.

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How about doing a AMA (ask me anything) on reddit? I think reddit.com/r/linux and reddit.com/r/ECE would be interested.

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or r/linux_devices (although this has a smaller readership)

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Will hdmi and USB Port be on the same side on model B? One could build a dock for monitor and keyboard than.

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No. I know there are lots of forums all telling us how they want it. Just assume the final model will be close to the Alpha board.

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I know a couple of these have been addressed in the forums but they seem to have conflicting answers/comments:

1. Battery Backup / Time Backup – You said above that this will NOT have a battery backup to keep time. Will there be a place for us to solder in a battery?

Power – What will the power jack be? (a 1/8″ phono jack like the Atari 2600?)

Power – What are the planned voltages?

Serial/Debug Port – Have you established the specs yet?

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1/ No and no. A battery alone would no help anyway you need a RTC.
As already said: power is still the main item under development. We hope to finalize that in a week.
It has a UART and unless you want to do something you will not need a debug port just as you do not need on on your PC. We used a ARM debugger for the first week. Never needed one thereafter.

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1. Will the boards be tested after the come back from the manufacturer or will that be done by the manufacturer? I read that Gert already got one board without working memory…
2. Who is the manufacturer? Does Broadcom has these kinds of PCB factories?
3. Will you publish the schematics?
4. What’s the hardest part of the PCB design?

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I can answer #2 for you – Pete’s company, Norcott Technologies, will be making the boards. Broadcom don’t have any involvement.

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1/ Yes boards will be tested.
2/ (see below)
3/ Not yet sure but as mentioned we will specify the GPIO port
4/ Good question (One of the better ones) the hardest part is to bring the signals away from the BCM2835. In fact that is 95% of the board design effort. The routing is extremely dense and requires that we use micro vias and small track width and track distance. All of which pushed the price of the board up.

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Are there any entropy sources on the board?

Also, how much power is available on the HDMI port’s 5V line?

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No.
Power: see previous answers

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Sorry forgot to answer the HDMI power question and I really, really want to because it seems to be a source for a lot of confusion.
Answer : 55mA.
Most people think you can power thinks from it but you can’t. 55mA is the current prescribed by the HDMI standard and the connected device is allowed to draw maximum 50mA.

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What’s been the biggest headache in terms of PCB design? Are there any features that you really really wanted to incorporate but just couldn’t? What’s the thing that *will* be in the final product that you’re most proud of?

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Sorry, I did something wrong in my reply. See 2 entries down.

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I have three questions to ask today. questions I hope may be incorperated into the Q&A.

first I am wondering if the board will support non-hdmi touchscreens. usb controlled ones are far easier to find… at least for me
second. I am wondering if wifi adapter compatibility will be added into the final board.
And third… when exactly do the boards come out? I have been keeping an eye on RP for some time and really like the idea of a computer so cheap and small, I could put it in my toaster if I wanted.

Thank you.

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Yes you can connect non-HDMI touch screens. (Sorry but is that not like asking for a sandwich without cheese?) No, there will be no wifi on the final board. We are still on track for November.

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See answer 4 above: BCM2835 signal fan-out.
We will not be able to bring all GPIOs out. Some come from the middle of the BCM2835 ball grid and would require buried vias. That would push the board price up too much for batches of 10K. (It is OK if you make a million)
I am most proud of the ARM. It was initially not in the design but we bolted it in place with four persons in about a month, including layout and verification.

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If the ARM wasn’t in the design, what was?

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I think Gert’s talking about the design of the BCM2835, which he was on the very small team for, when he refers to the ARM; not the Raspi.

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Ah, OK, so it was when an ARM was added that it became a contender for RPi’s SoC.

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Exactly. It’s surprising how few affordable apps processors on a chip are out there.

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As Liz said – the 2835 is basically a Videcore IV with the Arm11 bolted in (And Gert was on the team that did the bolting). It’s why it has a rather unusual boot sequence – the chip is a GPU with added Arm goodness, rather than an Arm with added GPU goodness.

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The GPU and lots and lots of multimedia peripherals.

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As with what happened with Liz’s Good News About Audio, has there been any other eureka moments that really helped push the maximum out of your hardware?

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Not in pushing more out of the hardware more in: We can omit another component. Or: We can use a cheaper version of…
I never did a cost reduced design before, only high end PCBs where cost was not a factor. Finding that 10uF in 0805 is ten times cheaper then in 0603 was a surprise to me. I did not know that for cheap stuff (resistors) the robot placement cost is as important as the component itself. We found we could replace two 100uF caps with 10uF. I learned a lot from that.

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Hi Gert;

1. Has any testing been done towards thermal coping of the device being run at full whack for extended periods of time in high heat environments? I plan to use it in an in-dash automotive environment where temperatures can fluctuate greatly (example; sun shining on a black dashboard results in quite high temperatures).

2. Same scenario as above but in terms of vibration/shock, we do have a lot of pot-holes here in the UK as I’m sure you’re aware ;)

3. Although probably a driver and not a hardware question, do you know if the GPU/HDMI output will support screen rotation with 2D / 3D acceleration?

Ps. Couple of questions for the lovely lady Liz, will there be a maximum order quantity allowed when released to the general public? And what is the lifecycle of the RasPi? Will it still be available for sale in 1/3/5 years time?

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1/ Yes the Broadcom packaging team have done full thermal simulations (Its good to work for a big company which takes it’s quality seriously. Difficult sometimes, but good) and we have been running these devices ourselves in ovens.
2/ That is more about PCB and connectors. So I can’t guarantee anything there.
3/ I think it can but don’t ask me how.

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…and, hypothetically, how much extra would it have cost to have put a VGA output on there..?

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Relative a lot as we only have HDMI to start from. I says relative as we start from $25 so adding $7 for chip and then the connector and before you know if you have 1.5 times the original cost.

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Are you going to come out with a version that will have WIFI?

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I’ll take that one: no, not planned, i.e. not in the next 6-12 months.
Wifi via USB works.

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You said above: “We will not be able to bring all GPIOs out. Some come from the middle of the BCM2835 ball grid and would require buried vias.”

Wild question. Any chance to get some/all of the remaining GPIO to the bottom layer as blind/through hole vias or pads for us with hardcode soldering skills and skip masking for them?

If not possible, maybe throw in a few thermal vias to lower the working temp further?

Kudos for all your work.

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How about bringing them mystery signals to bottom layer and letting us use a mating daughter-board to collect the signals …. maybe using elastomeric connectors, or bed of nails or conductive tape or conductive glue ….. or sumthin
99guspuppet

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You can’t solder to a BGA which has already been put down.

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Sorry re-read your question. No, we will need the via space to route other signals out. (Every via you put down is a signal blocker. Unless you use blind/burried vias where you can use the space at a different layer)

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I was pondering buried vias

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Another 2 questions:

1) what is the shutoff voltage for the Pi? Eg. If it falls below 6V or goes above 24v, is there some component that prevents the Pi from under voltage damage and/or exploding into flames? (also, it will help to know when designing circuits for battery powered Pi’s, where the Pi can shutoff when the batteries are exhausted).

2) when the gnu firmware is loading, is there any logo output, or do you get a blank hdmi output screen until the kernel kicks into gear? I was thinking it would show splash screen as it read the gpu firmware then the kernel info messages would take over. Is this so?

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1/ Supply/voltage is still under development
2/ The boot time from the GPU is so short you hardly notice it.

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Liz, it’d be nice to see a full boot video at some point, from turn-on to Debian desktop (it is Debian you guys are using at the moment isn’t it?) at some point :)

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I’ll try to do one, although my development SD card means the boot is pretty slow at the moment. And I use a console not a desktop.

So, perhaps I’m not the best one to ask….!!!

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I hear you. I’m waiting for the delivery of a new video camera today, so I should be able to get some proper, working footage for you all at Maker Faire on Saturday.

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I would like to see the RP logo as the first thing you see when booting up

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1. Although supply/voltage may change in the final release, will there be a brownout detection circuit like there is in AVR (ATMEGA) uC’s?

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I asked about brown out detection but by the looks of it there isn’t.
I guess you could put some form of brown out detection on an expansion board.

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Hello,
I would like to ask about heat generated by this board. I don’t see any (big) radiators nor fans on the videos – will it be okay this way running 24h/day playing HD videos or doing other CPU-intensive tasks? Or will it need extra cooling?
Thanks

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You won’t need extra cooling. The board only draws a watt of power – if you watch the video from the Transfer Summit, you’ll see that the board has been running HD video for eight hours. Its thermal equilibrium is just above body temperature.

The Raspberry Pi stays nice and cool because the SoC we use is designed for mobile telephones, where heat and power consumption are important. So you won’t need any heatsinks, fans or anything else for cooling.

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Is this going to be able to run FreeBSD or at least NetBSD? And what about other systems other than linux?

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I believe you will be able to run alternative OS’s. Someone is certainly looking in to one I cannot talk about! Not sure of progress.

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Would that be Windows 8? (Sorry, just had to tease with that!) :P

Still, that would be a nice feat if the Raspberry Pi did Windows 8… I’m sure I’ll be busy working on a touch-based linux OS when I get my ‘pi.

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Windows 8 will be a big nono. In order to run Windows 8 the system would have to be locked down so it cannot run anything but Windows 8: “…Microsoft will also require that manufacturers offer the ability to turn off the secure boot feature on x86 hardware, but they must not offer such an option on ARM hardware.” (Wikipedia)

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It sounds (from the Wiki) like once the bootloader has done its job, you can load whatever you want. However, FreeBSD’s non-x86 support is still very immature compared to e.g. Linux, NetBSD, etc; I’d say you’re likely to have more luck with those.

Given that the bootloader allows you to load whatever kind of kernel you want (again, according to the Wiki), this might make a very nice platform for teaching OS development! Even if documentation for the non-secret parts of the chip (e.g. everything but the GPU) is spotty, the Linux kernel code is available to examine for at least rudimentary device drivers.

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Raspberry Pi is a USB host, not a USB device. Why? What is the way to connect for example external usb hard drive to it? Maybe Raspberry Pi should have possibility to connect different AC adapter with USB 5V line?

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It’s a full computer not a device – computers tend to be hosts.

External USB hard drives work fine.

USB power questions and answers can be found in the forum.

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Actually BCM2835 can act either as a device or a host, but since the LAN9512 device is being used then it is locked into host mode, that is one disadvantage of the OTG specification (although not the only one!)

Maybe Gert can comment on the Model A, since that doesn’t have the hub and therefore could work as a device (if VBUS is disconnected)

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Hopefully this thread is still being watched.

Regarding the USB host/device question, that sounds like I could not use the R Pi to go out to an internet host for some files, and then have another computer connected through USB read those files. Is that correct, or is that something that would be possible with some work?

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The Ri can quite easily access the internet – either the local ethernet on the model B or a USB wireless adapter.

You could then connect the Pi to another computer via another wireless adapter, or perhaps even bluetooth, or again by the ethernet connector. Direct connection USB to USB won’t, I think, be possible on the model B. It’s theoretically possible on the A, but it’s not been tried and might not be actually possible without a hatload of work.

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Just a couple of quick questions about the board layout.

1. What is the DC Power connector spec? 2.1mm Centre Positive?

2. The details of the mounting holes? If I wanted to mount the R-Pi on threaded standoffs, I would probably use something like an RGA M2.5 x 6mm (or similar). These require a pcb hole size of 2.5mm and a clearance 5.5mm dia around the holes. Is this set yet?

3. Are any of the mounting holes plated and connected to GND?

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Sorry, I can’t answer any of those questions yet as they require details from the next revision PCB which we have not got yet.

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What’s with the distribution of the Rasberry PI? Will I be able to buy one in my favourite onlineshop?

-No guaranty for correct spelling and grammar I’m from Germany, ;-)

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If your favourite online shop is this website, then yes.

If not, then no (for at least the first batch).

Lots on information in the FAQ and wiki of availability, where it get it, when etc etc etc

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Does the BCM2835 include any analogue to digital converters? available timers, counters?

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No on AD, Yes on timers, No on counters.
I don’t know how many timers are in use by the SW so can’t give a number for available timers.

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Thanks. I2C will make up for no AD. I’ll look for I2C counters.

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If I wanted to use a different OS – what information would be made available about the BCM2835 to allow this OS to make use of it?

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That is SW. I know only about the HW.

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First things first:
This is ace. The whole project is brilliant, thank you for putting the hours in and I can’t wait for the board to be released.

This has sort of been covered before, in the deepest sleep, what would be the rough current draw? I read earlier that there is no internal watchdog, which I assume means that you can wake up the proc with an external interrupt? or is there a timer that works in the lowest sleep level?

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Interestingly that is a question I often get from our ‘regular’ customers. I have given answers to that which later turned out to be totally wrong because their idea of ‘sleep’ was different from mine. For example: do you want to keep your SDRAM contents? That required refreshes! So the unsatisfactory answer is: depends an what you want to keep running.

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Regarding a hardware case question, will you be selling (as an optional) a suitable case to enclose your finished circuit board based computer? If not will you be specifying suitable minimal enclosure details for normal operation, i.e. mounting measurements, minimum distance between cct board and enclosure, height, temp range/coefficients, compatible enclosure materials (plastic, aluminium)?
Finally for certain projects (ie those involving water) it may be required or necessary to seal or encapsulate the whole board (to make it water tight) would this cause an issue?

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We certainly will. We can’t start designing a case until the final artwork is back (Gert and Pete are still sending the schematics to and fro and optimising them, so it’ll be a couple of weeks at least). We’ve decided to hold back on designing and manufacturing the cases until after launch, so they don’t hold things up; we know that many of our initial customers are going to be hobbyists who won’t want a case in the first place.

All the data you ask for above will be made public when we have the artwork back for those who want to hack their own cases. We don’t foresee any problems with sealed cases.

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Is the expansion pinout finalized yet if so can it be made public?

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Not yet, I’m afraid. It should be a couple of weeks before we can let you know, but you’ll be able to read about it here.

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Not really hardware related, but…
1) How many devices will you initially manufacture?
2) Considering the vast number of people interested in buying at least one device do you see any potential initial supply problems?
3) Is there going to be a cap on individual orders initially to avoid people buying massive amounts of stock and then touting them on fleaBay at an inflated price?

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I can get these ones:

1) Our first batch, for reasons discussed at great length on the boards, will be 10k. Production will be fast, so we’ll have a pipeline going very quickly.

2) Supply problems – well, we’ve been talking about this, and haven’t come to any firm conclusions yet on how to manage it, although we have several options open to us. The winning suggestion at the moment is to limit sales for the first two weeks only to those who are prepared to buy-one-give-one. After that, it’s open to everyone. As I say, this isn’t confirmed yet, but it may well be the way we keep demand sensible at the start; we’re anticipating massive demand initially which we expect will taper off quickly once the hobbyists have their hands on one.

3) See 2)!

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If I want to buy one, give two can I have the first one off the production line?

Will each board have a serial number
If will it be available electronically (similar to a MAC address)

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Although the device’s USB is USB host can it be be turned into USB client (OTG) in a similar fashion that the PXA2XX can be. Using a combination of a cable, a resistor (added or removed depending) and some register manipulation?

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Definitely NOT on the B version. According to the specs it should be possible on the A version but we have no SW for that. Because we have not tried it I don’t know what happens after reset because it will start as host and then needs SW to go into slave mode. So that alone might upset your system.

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Yeah, so it should handle device mode and we’ve had it working before with RTOS drivers no problem. But we’ve never had the linux device support working (or more to the point never bothered trying!)

So theoretically it’ll work as long as the VBUS is disconnected…

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I assume the extra chip that hands out the ethernet gets in the way on the model B. i’ll have to give it a go on the A when i get one. it can’t hurt to give it a try

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Pretty sure this is a stupid question, so forgive my n00byness. I presume there is no kind of BIOS on the board and absolutely everything is run off the SD card. Does that mean there’s no need to flash anything for updates / fixes to the board itself and we can just tinker with the SD card with no risk of bricking the device?

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Exactly so. Good, innit? ;)

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I’m pretty sure my subconcious will come up with an inventive way to brick one. We’ll see.

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Q: Will an Arduino Uno device be able to talk/pass information to/from a Raspberry Pi? May build autonomous project which uses Arduino for control and raspberry for other functions lacking in the Ardunio.

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Not sure anyone here has Arduino experience,. so I don’t think we can answer that question one way or the other.

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its has a ftdi usb serial adaptor that sits infront of a atmel ATmega*

The arm version of debian(lenny) supports it out of the box. So it seems likely that it should

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I’m not an Arduino Expert, but been doing some Microchip PIC development with other Linux Embedded boards, as long as you have SPI or I2C communication Protocol with some kernel/service/app support, it would be fine! Kind of a Master-Salve relation is quite simple, R-PI being the master, and other sensors/microcontrollers/arduino being the slave device. Using R-PI GPIO pin interrupts (if possible) you may get the Arduino to trigger a communication, but this will require a dedicated application in R-PI to manage this (just speaking from my head, please correct me if I’m wrong on this subject). This is something that I also will be trying, so, please expect some how-to on this subject!

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Ardunio’s should work with Rashberry pi.
– they interface via a standard USB connector and support Linux as a platform.
– I was thinking a Rashberry pi Ardunio Shield would be pretty cool.
I can check this Arduino / Rashberry Pi link out when I get a Rashberry pi.

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Are the RPi team looking into getting HDMI CEC working – or will this be left to the community?

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Again, HW questions only please.

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Are the kernels that you’re distributing stripped back and optimised specifically for the hardware present of the board?

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Sorry: Can’t answer that I do HW only.

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So if this is the case

Quote
“Pretty sure this is a stupid question, so forgive my n00byness. I presume there is no kind of BIOS on the board and absolutely everything is run off the SD card. Does that mean there’s no need to flash anything for updates / fixes to the board itself and we can just tinker with the SD card with no risk of bricking the device?”

Then are there hardware hooks for any other operating software to use for the various I/O?
E.g if a different operating system was to be considered, how would it utilise the USB and HDMI ports? (please excuse me if this is an obvious question), as I am trying to establish if the RP or RasPi (pronounced Raz Pee) can be used without Linux, TinySoft or Fruity (cannot bring myself to mention their names)

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Sorry that is a SW question. Try the forum..

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There would be huge problems doing this, the chip support package alone takes many man months to do. But if someone wanted to work out all the foibles of the USB hardware for example and try to port it to a.n.other OS go knock yourself out!

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I have been wondering if you could power multiple pi’s of one transformer. Has anyone considered that? If so how many do you thing you could run off one power brick connected to a standard plug?

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Yes you can. How many boards can you supply? Depends on the transformer. You can get them from 100mA (not enough for one Pi) to 1000A (you need a shed for one of those). There are a number of calculations to perform about voltage, wattage, amps etc. If your not familiar with them, I suggest you decide our how many board you want to connect and ask somebody who knows electronics to help you select the right transformer.

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I currently own a BeagleBoard xM, which overall I’m happy with (bit pricey!), however, the one thing that really annoys me is the positioning of the connectors. I understand that this is a cost and PCB layout decision, but it’s extremely difficult to work with it on a desk when there’s a cable going in all directions. I can’t bend cables or put strain on the connectors for fear of damage, so instead the BB takes up the vast majority of my desk. When designing a case, is it possible for the team to supply adapters/cables to re-route all connectors to the rear of the case? Personally, I’m not bothered how small or large the case is, in fact, I’d be happier with a MicroATX board that can be placed in a standard case than a tiny PCB with wires in all directions.

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I am afraid the raspberry Pi board will not be much different. As explained in the various forums the board is mostly needed to hold all the connectors. Putting them on one side/two sides would increase the area and thus the cost. The primary target user is and has always been those who want a cheap computer. It is for those users that the connectors have been placed: mouse, keyboard & SD-card at the front, video at the back. Ethernet and power wherever space it left. For your $25/$35 you get a lot of computing power and you have to accept some inconveniences.

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I’m really looking forward to building some hardware to connect to the GPIO on here; I have a wireless sensor network mote platform under development that should attach quite nicely. My question is what relationship the GPIO pins bear to the SPI/I2C pins. Are they exclusively muxed, a la many small microcontrollers these days, or do the serial interfaces exist alongside 16 I/O pins? Also, are there any power/ground pins in the headers? The motes should run on just a few mA, so one could feasibly provide the power through GPIO, but real power would be nicer.

I’d like to add one more voice to the pile of people advocating PoE in a subsequent revision, though I recognize that as not entirely applicable to many educational settings (particularly not the home self-directed learning setting, since most home switches/routers don’t supply PoE).

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As you expected some GPIOs also function as I2C/SPI. But with 16 GPIOs you will have some left for what you want. Or you can connect I/O expander chips to the I2C. That will give you many more GPIOs!
Yes there will be power and ground pins.

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Arduino question:
Not only can you communicate with these, via USB, or i2c or interrupts on the digital lines but as the ‘pi is running debian, the Arduino IDE will run on that and you’ll be able to actually program the your Arduino via the USB lead :)

I do quite a lot of work with Arduinos and this seems a pretty perfect marriage!

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GPU question this time: the video RAM for the gpu frame buffer. What happens there? Does the GPU eat various amounts of the Raspberry Pi’s system RAM (ie. 32Mb) for its purposes or does it have built-in memory of some sort?

Cheers.

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The SDRAM is shared by the GPU and the ARM. How much memory is used depends on what the GPU does. e.g. a 800×600 screen uses much less memory then 1080p.

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Are there any I2S pins available?

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According to the Wiki, yes.

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WIll the RP have the option to boot from anything other than the SD card(secondary options)? Like USB drives/flash sticks?

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You will be able to boot from USB drives too.

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could you use 1 without an sd card then?
Pen drive are cheaper than sd cards

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Hi there.
Quick qestion relating to the possibility of a radio device. (Even if as a peripheral via USB.) I’m asking due to an interest in adding a device that uses a low power consumption, modular radio for mid range wireless networking.
This question may make no sense if you’re unfamiliar with this line of devices.
I’m wondering if this is possible considering the additional devices power consumption that the board has been tested with and if the availability is there to integrate / connect such as device.

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You mean like the CC1101?

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Yes. That just might do itwith some handywork. Would it be viable to integrate this onto the board (if final unit size is a consideration)? Im unsure at the moment of the exact power consumption, bandwidths and frequencies.
The device in my mind is the new innovation from Rearden Companies “http://www.rearden.com/DIDO/DIDO_White_Paper_110727.pdf”.
May be of interest to yourself and the team, keep up the good work.

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No, we can’t do it on the board as the user group would be far to small. You can make a plug-in board yourself to connect it to one of the interfaces.

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Hey,
Can someone tell me if the OS is running from the SD or onboard?

If on-board how are you loading it?

thanks

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A quick question: I think you are using a chip with stacked memory (ie memory and processor in the same package). Do you think you would have been able to make Rashberry Pi if you didn’t use stacked memory?

There would have been a lot more high speed signals to route, you would have needed more layers at lease I would have thought.

Its interesting because I have talked to other companies and they don’t see the benefit of stacked memory.

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There are many factors to this. The board area gets smaller and the board lay-out simpler so that is lower cost for the customer. Also the number of balls at the bottom of the device gets lower which can be used in two ways: Smaller package or larger ball distance. The latter again means you have lower PCB cost. All advantages to the customer. But to produce these type of devices you production cost is higher. You have to go to more layers on your substrate (The tiny PCB which holds your die and balls) Next major cost increase for manufacturing is testing. Think of the technique required to test both the bottom AND TOP of the device. Those costs are less a burden if you sell millions of those devices. The PoP (Package on Package ) technique is only starting to emerge so customers will not yet see it as ‘the standard way of doing things’. This makes it easier for companies who do not want to take the risk or cost for this to convince the customers to do it the ‘standard’ way.

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Hi again Liz, and hello to you hardware guys!

So we now know we will get GPIO, SPI, I2C, UART.
Does that mean there will be serial and JTAG pins?
Will we be able to access the bootloader?

So far all the ARM devices I have used have needed either modification of the U-boot environment variables, or replacement of U-boot itself, to obtain the required functionality I require (ability to boot from various types of drives, internal flash, or SD, etc.) Will we be able to do that on this board, or is accessing the bootloader itself a no-go? If the main bootloader itself cannot be altered can we chain two a two-stage bootloader? Otherwise how would it be possible to use partitioned storage?

One more question. Happily it appears the Videcore on this SoC is the same or similar to the one used in the Roku2. So I am thinking I might be able to use this board as a MythTV frontend in conjunction with my Seagate Dockstar and GoFlex Net Debian MythTV backends. Does the ARM core and Videcore IV have enough decoding power to play back a full 1080p mpeg2 or mp4 stream? Please say yes!!!

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From my phone in the airport; there’s dedication for you!

Yes on the pins. There isn’t really a bootloader, though we expect someone will probably implement one; right now we boot to a bare kernel.

The ARM core probably doesn’t have decoding power you need, and while the videocore does, we’re currently debating whether it’s worth spending the charity’s money on licensing fees for all the codecs. We’ll definitely have h.264 video w hardware acceleration, but I can’t make any promises beyond that at the moment. (I have all kinds of angry stuff to sat about licence fees in a later blog post, once we’ve finished negotiating.)

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Thanks for your dedication Liz! I hope the phone was an N900 or at least an Android, and not an iPhone ;)

The pins and bootloader info is good to hear! If there is no bootloader by the time they ship then I may try to compile up a U-boot for you once I get my hands on a board.

The ARM core alone is definitely not powerful enough for a MythTV frontend. But if the Videocore will support h.264 that would be adequate for many of the streams. I thought we could get around mpeg license fees in the EU. I would think that at least for educational charities there should be some type of deal that could be made. Hopefully at least there might be some way users could create some type of repository for the mpeg codecs once they have their hands on the boards. That is how Debian, Fedora, etc. do it with their distros. I don’t think either these boards or even my Kirkwood boxes have enough power to transcode everything to h.264. . .

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I understand your pain about codec licensing issues.

As DVDs are MPEG-2, it would seem that there is a lot of stuff that would be possible for students to do with DVD data (from a variety of sources) that won’t be possible without an MPEG-2 decoder. (I realize encoding is going to be slow either way.)

I’m thinking “what interesting things could I do with the computer I purchased in 1998 that I won’t be able to do with this one?” Most of those things require a hardware MPEG-2 decoder, just like they did in 1998. :)

I guess to me, for student usage, the ability to play MPEG-2 at DVD resolution and bitrate would be more interesting than the ability to play h.264 at 1080p. Then again, maybe I’m an old guy. :)

For those of us in the US, MPEG2 support is even more of a big deal because digital TV in the US is in MPEG2. I realize it’s more complicated in Europe. Certainly there are some interesting projects that could come from recorded TV broadcasts.

Due to US digital TV, MPEG-2 at 1080i/720p is worth almost as much to me as h.264 at 1080p.

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I believe if, as an integrator, you license MPEG4 from MPEG LA you get MPEG2 included.

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It’s been mentioned a few times that the RPi will provide a UART, but I’m a bit unclear on the details, with the wiki talking about USB UARTs and the mention of a “Broadcom virtual UART”.

By UART, do you mean a typical RS232 “semi-compatible” pin header like the one found in many embedded systems (running 3.3 V instead of true RS232 levels, with 3 or 4 pins providing Rx/Tx/GND only), or are you talking some other kind of UART?

(I’m interested in the possibility of connecting a RS232-driven peripheral without having to throw in a USB-to-serial adapter.)

Thanks,

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It’s the usual kind of semi-compatible UART header. Not sure where the virtual UART info came from initially; there is a debugging tool we use internally that might meet that description, but it certainly won’t be exposed in the final board. (The other end of the virtual UART is in the GPU, and you’re not going to be delving in there!)

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Great, thanks. Looking forward to November. :-)

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Hi there.

I wanted to ask two questions:
1. Will there be SATA Connectors implemented in Final BoardLayout (I dont know if the CPU is supporting SATA Connections)

2. Are you considering to implement a MiniPCI Slot so this board will give the options to use MiniPCI Slots so we can enhance the functionality?!

Greetings from Hamburg, Germany

Ron

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Unfortunately the answer to both your questions is no.

As standard You are limited to the SD card slot, things that plug in to the USB (including hard drives which will work fine), and on the model B, ethernet.

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What is the max side sd card we can use on it ?

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I meant max size

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I believe up to 32MB has been tried, although we have had problems with some makes of cards of that size – this is still being investigated.

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Just to clarify, did you really mean 32MB or did you mean to say 32GB?

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32GB, soz.

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Ah, cool – phew!

I thought 32MB was a bit odd nowadays!

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From Wiki:
“FAT32″ :o ” . . .partition with GPU firmware and a kernel image”

FAT32?? Say WHAT? What is up with that on a Linux board?

Why not UBIFS, JFFS2, or at LEAST ext2/ext3?

FAT32, huh? For the firmware and kernel partition no less!
I anticipate forthcoming reliability problems with that partition. . .

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If it were anything else, it wouldn’t be accessible from a Windows machine, making it more difficult for people (specifically developers) to put images on it.

I’ve been using it fine for some time – no reliabilities problems so far. FAT32 is pretty reliable AFAIK. used on lots of machines and USB drives with no problem, and as long as you circumvent the patent issue there are no other problems with using it.

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This is going to sound like a “why doesn’t is support feature X?” question, but I don’t mean for it to be taken that way.

How did you come up with the memory amounts for the device (128MiB for the model A, 256MiB for the model B?) Was this purely a cost thing, or was there some analysis that showed that this was a pair of sweet spots in cost-performance? This is noticeably lower than current cell phones, where 512MiB seems to have become the norm, so I’m sure cost was part of it.

I’m particularly curious why you decided to have two different memory amounts, as I could see this causing some applications advertising “works on raspberry pi!” to only work on the model B.

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The PoP packages used for memory are really only available in 128 and 256 packages. There are 512 but they are rare and expensive at the moment.

128MB is used on the Model A to get price below $25 – the extra on the Model B cost a few more $’s.

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1) With no onboard data storage, how does the GPU go about starting the boot process? Is there something hardcoded that allows it to mount and read the SD card?

2) Was booting RasPi without NAND/NOR uniquely difficult, or is this common with ARM chips?

3) Any interfaces supported by the chip (e.g. audio input) that you could not physically fit/be routed on the board?

4) PCB routing difficulties – are these common with similar SoCs or due to the unique RasPi size?

5) Do both HDMI and composite outs work simultaneously or does one have to be selected in software? (I’m guessing the composite video puts out whatever’s sent via HDMI downscaled to 480i …)

Thanks for keeping us informed, this is such a great project!

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The GPU has a boot rom (i.e. hard coded into the chip) that understands FAT16 and FAT32. This was originally included in the boot options to allow easy demonstration of the devices (and to speed development as it only requires the copying of files to a SD Card and not reprogramming NAND / NOR).

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1/ As Steve H says: code in boot rom
2/ You need and SD card driver in bootrom
3/ We cut down on GPIO pins.
4/ These are common to most high density BGA package nowadays.
5/ Plan is to auto-detect HDMI and switch to composite if not present. That code is not developed yet. I assume for composite we need a ‘press key until you see a picture’ mode to go trough all the world standards.

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Perhaps silly question: main difference between A & B = memory, secondary is i/o. Does that mean that (apart from memory) the only difference is the connectors, or are other components also missing, or are the board layouts also different? I’m sure I read somewhere (can’t find it now) the connectors are all through-hole so could be removed to reduce board height, and that could mean A was better for me than B (fewer connectors to remove!), but if there are other differences ….
Sorry if you’ve already answered this – put this post into write-only memory

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Spent all today reading through 10,000 posts, then asked this question. Back to the front page, there was most of the answer. So please consign this to WOM

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What’s the architecture of the GPU? Is it tile-based or immediate mode?

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Haven’t use something other than x86 computers PCs before, so I am wondering, will any USB WiFi dongle supported by the Linux kernel work on Raspberry, an ARM computer?

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Yes, list of ones I tested on the Wiki.

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Which VIC is in use please? The 190 doesn’t seem to fit what information we have on addressing?

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