Slashdot Mirror


Raspberry Pi PCB Layout Revealed

An anonymous reader writes "Yesterday, the final Raspberry Pi printed circuit board (PCB) layout was revealed. The word 'packed' comes to mind as this is one very complicated looking board. The reason for that is just how much Raspberry Pi has strived to save money on the machine by using complex routing to keep things small and cheap. The Raspberry Pi team don't believe the design is going to change again unless they missed something. With that in mind, they revealed the final board is exactly the same size as a credit card, measuring 85.65 x 53.98mm."

42 of 112 comments (clear)

  1. Screen and keyboard? by lordmetroid · · Score: 5, Funny

    How am I going to use this computer without a screen and keyboard?
    I demand a credit card sized keyboard and screen!

    1. Re:Screen and keyboard? by vlm · · Score: 5, Insightful

      How am I going to use this computer without a screen and keyboard?

      I demand a credit card sized keyboard and screen!

      Thats called a "cell phone"

      --
      "Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
    2. Re:Screen and keyboard? by ColdWetDog · · Score: 4, Funny

      Is that a "whooosh" I hear?

      He's probably on AT&T - he won't hear anything.

      --
      Faster! Faster! Faster would be better!
  2. Complicated? by thoughtspace · · Score: 5, Insightful

    Huh? What's complicated about that board? Looks pretty normal.

    1. Re:Complicated? by Austerity+Empowers · · Score: 5, Informative

      I would go as far as to say that looks like one of the simplest and least complicated designs I've seen. Also it should be noted that small and cheap compete with one another. Cheap things they that cost space- fewer routing layers (components & traces often need to be farther apart for impedance & via room), using larger components (0402 or bigger generally), not using blind/buried vias, using routing space for power. Small things they did that added cost- front/back side assembly, through hole components on a mostly SM design.

      It looks like a fairly simple design. I'd try to get rid of the through-hole stuff unless it's just debug, that adds a step in mfg which can raise cost and also causes place keepouts to eat up valuable real-estate.

      The post should have raid "Board layout review, all slashdotters attend".

    2. Re:Complicated? by mla_anderson · · Score: 4, Informative

      Actually looks pretty slack with lots of space. However to make it inexpensive requires much more care in the design rules and routing. Placing and routing a board with tight component clearances and tight trace and space is easy and expensive. Taking the same components on a small board from 0.1/0.1mm trace and space to 0.15/0.15mm trace and space takes a lot of work, but can significantly reduce the cost to manufacture.

      From an initial view, the biggest cost adder I see is components on the solder side. There don't seem to be too many on the bottom side and with a bit more work it could probably be made into a single sided board. I'm working on a cost sensitive board right now, and one of the big things we've done to cut cost is make sure all components are on the top side. (Low cost is relative, this BOM is many many times the projected price of the R-Pi.)

      --
      Sig is on vacation
    3. Re:Complicated? by ebenupton · · Score: 5, Insightful

      Would be great to get all the components on the top side. Unfortunately, you pay for that in extra track length between the SoC decoupling caps and the BGA balls. I believe Beagle and Panda both do this with their OMAPs, and (mostly) get away with it, and we may investigate it in a later revision; in general departing from datasheet recommendations makes me queasy, even for a chip I worked on...

    4. Re:Complicated? by TheRaven64 · · Score: 2

      This machine is the spiritual successor to the BBC Micro. I have here the BBC Micro User Guide, which has hand-drawn circuit diagrams in the back. In comparison, this board is very complicated. In comparison to anything modern, it's pretty simple.

      --
      I am TheRaven on Soylent News
    5. Re:Complicated? by muon-catalyzed · · Score: 4, Interesting

      Except nobody noticed that it is just one extended socket for the massive proprietary Broadcom BCM2835 chip (SoC) that provides pretty much everything, so this is 90% Broadcom thing, the UK team just provides fancy packaging and folklore. Does anybody know the price point of that Broadcom silicon?

    6. Re:Complicated? by rec9140 · · Score: 3, Insightful

      "What concerns me more is the "proprietary" aspect. How many of the chip's features will be accessible by hobbyist developers? Will we be receiving full public documentation on how it works?"

      No, getting data sheets from most silicon makers today, is tanamount to asking for state secrets,err...ok not such a good example, well not hapenning... and don't mention to the Pi people.

      See:

      http://www.raspberrypi.org/forum?mingleforumaction=viewtopic&t=1077

      --
      1311393600 - Back to Black
    7. Re:Complicated? by mirix · · Score: 2, Informative

      It doesn't really matter what the chip costs alone, as you won't even get a fucking pin diagram out of broadcom without a large order and an NDA.

      --
      Sent from my PDP-11
    8. Re:Complicated? by mla_anderson · · Score: 4, Informative

      Generally if the small caps are close to the package and tied to planes (I'm assuming there are planes) with short thick ties to reduce inductance you can get by with it just fine. The bulk caps can be quite a ways away as long as they are also tied directly to the planes. We're running some very high speed stuff this way without problems. Xilinx has some good info on bypass caps and how they can be placed in their Spartan 6 docs.

      If there's no planes then you have to have the relatively thick tracks already for current carrying capability, but the inherent inductance could possible give you an edge in filtering as long as you're not yanking the individual pin levels out of tolerance.

      --
      Sig is on vacation
    9. Re:Complicated? by Savantissimo · · Score: 5, Interesting

      Yet other manufacturers don't take that attitude. Go look at TI or Analog devices. Full datasheets right there, often running to hundreds of pages reasonably priced development boards, often free samples. Broadcom claims to have features such as DSP and GPU built in to this chip, but I don't know what use they are supposed to be if they are totally undocumented. Supposedly about 98% of the FLOPS in this thing are in the GPU, but good luck getting at them.

      --
      "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
  3. Re:Features? by afidel · · Score: 4, Informative

    ARM11, specifically ARM1176JZF-S 700-megahertz which is a component of the Broadcom BCM2835 SoC.

    While it's cool that they got the cost so low I'm kind of sad to see all those SMC's, kids today can't get into building electronics because so much stuff has gone to stuff that you just can't solder by hand. Yes, I know you can still use microcontrollers with breadboards, which is cool if you want to make a simple robot, but stuff like building your own computer that you can hook up to your TV and use like any other computer would be very cool as well.

    --
    There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
  4. complex routing ? by alvieboy · · Score: 5, Insightful

    At first glance, this looks like a normal routing with a 4-layer board. Eventually 6, if you add proper ground + power.

    There's nothing indicative of PCB parameters, like drill sizes, clearances, blind/buried vias, minimum trace width, so on. Again, a simple look reveals nothing but common parameters for PCB.

    Again, TFA is biased.

    1. Re:complex routing ? by ebenupton · · Score: 5, Informative

      As I understand it, the biggest challenge was escaping a 0.65mm BGA without using significant amounts of HDI on a 6-layer board, while keeping good solid power and ground planes and large (i.e. cheap) track and gap specs. Relax more or more of those and it is indeed trivial - our alpha boards were done in about four days by doing exactly that.

    2. Re:complex routing ? by ebenupton · · Score: 5, Informative

      Off the top of my head, we save around a buck at 10K-off through a combination of 6 layer, coarser T&G and limited HDI. Figures for UK manufacture; YMMV in elsewhere, particularly in the far east (where cutting edge volume manufacturing is much easier).

      The particular stack-up we've chosen is only one possible cost minimum; I've heard it suggested that 8 layers with zero HDI is quite competitive for 0.65mm BGA.

    3. Re:complex routing ? by dotbot · · Score: 2

      Looks pretty pedestrian to me (although a BGA breakout on so few layers is worth a tip-of-the-hat). I think I only see three signal layers; blue, yellow, and reddish-brown.

      Is blue really a signal layer? Looks like blue and pink are silks to me and the board is simply double-sided.

  5. Also that size... by X86Daddy · · Score: 4, Interesting

    Penguins and Altoids tins happen to be about that size as well... I wonder how well a populated Pi will fit... if so, awesome little PC cases!

  6. Re:Repeat much? by Anonymous Coward · · Score: 3, Insightful

    I'm fine with this. R-Pi is worth it.

    This could make a pretty big change for computing hardware and software learning.
    Too much is done on overbloated hardware where you aren't even exposed to said hardware.
    Most people in computing don't even understand the very basics of yester-2-decades-agos knowledge.
    The most they touch on it sometimes is throwing together things in Java, if they are lucky.

    It's all fine and well if you can do X on a really powerful computer, but being forced to do it and have noticeable slowdown or inefficiency in code by not doing it is a HUGE difference.
    Having limits forced on to you in order to design efficient code is the best way to design said code.
    But most developers these days are absolutely atrocious at their work, abusing the hell out of hard drives, flooding your RAM and page files with crap all over the place because they feel that their program has more worth than another persons program.
    Worse when they do all that AND LAG LIKE HELL. (STEAM! DAMN IT VALVE FIX THAT CRAP ALREADY)
    PEOPLE. MULTITASK.

    I'm hopeful for the next generation of developers actually having an education on this, as well as possibly other similar boards. (admittedly a little on the expensive side in comparison)
    So many lost techniques with all this high-level abstracted knowledge.
    It's like building the frame of a car without the body. Sure, people could push it, people could pull it, hell, they could roll it down a hill. Still doesn't work efficiently.

  7. Not so packed by dpaton.net · · Score: 3, Informative

    Really, it's not. I do stuff like this every day. It looks pretty normal for a 4-6 layer board with a BGA or two on it. TFA needs to learn about what modern design standards are. It's only complicated if you still lay boards out with ruby tape or a sharpie.

    --
    This is not a sig. this is a duck. quack.
    1. Re:Not so packed by inflex · · Score: 2

      The trouble with this sort of reporting is that it betrays the work done daily by people who really -are- dealing with complicated stuff. Reminds me of parents rabbling on about their "genius child" because the kid installs software O_o.

  8. Re:Amazing by ZeroSumHappiness · · Score: 3, Informative

    1080p30 using h.264 is the top specification.

  9. Re:Features? by QuasiSteve · · Score: 4, Informative

    While it's cool that they got the cost so low I'm kind of sad to see all those SMC's, kids today can't get into building electronics because so much stuff has gone to stuff that you just can't solder by hand.

    While I'm with you on this on many levels (remember building things with the 4000 series? Yeah, we don't do that anymore. Haven't since PICs. We just write some code that does the job much better), I wouldn't say that kids can't get into it anymore.

    SparkFun, for example, regularly organizes PTH and SMD soldering classes as well as offering kits for both. Some SMD you can solder by hand quite easily, others you can get a nifty breakout board that lets you easily seat the SMD IC and melt solder up to its leads ( http://www.youtube.com/watch?v=-32orELxkpE ), and yet others you get some solder paste, a syringe or a toothpick (seems popular), put the paste on the pads or dip the leads in the paste, put the part on the PCB, and then stick it all into your toaster oven.. or on a skillet.

    Of course for most kids, just playing with e.g. Arduino and some shields/sensors is going to be a great way to get into electronics in the first place.. then when they need something that's not on the market they can explore PCB design, soldering, etc.

  10. Re:Features? by tlhIngan · · Score: 4, Insightful

    While I'm with you on this on many levels (remember building things with the 4000 series? Yeah, we don't do that anymore.

    Why not? The CMOS 4000 series and TTL 74xx series is still around, even in the various combinations (74HCxx CMOS, 74HS, etc). They're still availble from Digikey and the like, and many designs actually use them still.

  11. Sweet. My dream Halloween costume comes closer. by Commontwist · · Score: 2

    If I could ever easily design a non-expensive Sci-Fi armor suit that has redundant, networked computers, streaming video-to-internet from a helmet, real-time video display in helmet, easily detachable web cam/mic/speaker modules that can be used on or off armor, and able to be worn from -50C to +50C I would build it for my Halloween costume and stream visiting Halloween parties to a web page. Reusable for comic and anime cons too. Heh.

  12. Re:Repeat much? by TheRaven64 · · Score: 5, Funny

    Slashdot has become an RSS feed for the Raspberry Pi blog

    Yes, how dare a site that claims to be 'news of nerds' cover a project to build a cheap computer designed to be interesting for school-aged nerds to play with? I demand more Apple stories, and political news!

    --
    I am TheRaven on Soylent News
  13. What a wonderful project! by Hobart · · Score: 4, Informative

    ...and yet, just like the OpenMoko FreeRunner (giant opaque SMedia Glamo blob meant 2d VESA grade graphics only) and the OLPC XO-1 (giant opaque Marvell blob meant the whole WiFi subsystem and "mesh-while asleep" was all a black box and driver couldn't be troubleshot) , all the software is "open" yet obfuscated

    The entire Raspberry Pi depends on a gigantic proprietary blob from Broadcom.

    Hmm. Google search came up with this deviantart for "Raspberry Blob", maybe this can be the project's mascot. Hooray for undocumented blobs, we don't need source code, maybe we'll get Windows CE for it someday!

    --
    o/~ Join us now and share the software ...
    1. Re:What a wonderful project! by Jamie+Lokier · · Score: 3, Interesting

      all the software is "open" yet obfuscated

      The entire Raspberry Pi depends on a gigantic proprietary blob from Broadcom.

      So let's do a Nouveau-style reverse engineering project. How hard can it be?

      Sounds like a perfect project for the target audience: curious and talented kids. With a bit of experienced help if they get stuck (seems unlikely to me though, with sufficient time & motivation). Some kids love reverse engineering. I did when I was young and I was far from the only one (but we didn't have an internet to meet each other back then).

      (I did loads of reverse engineering from about age 11+ (that was 1983), starting with the BBC and moving on to everything I could get access to, pulling apart games (starting from the binaries), changing behaviours, porting them from tape to floppy disk ;-), even porting them to new architectures, and now I think about it, quite a lot of hacking on video hardware of the time, both in hardware, and quirky programming to make it do useful things it wasn't designed to do. If Mr Braben is listening, I printed a whole disassembly of Elite, BBC disk version on dot matrix that took days to print (wow just got a flashback), and spent a long time learning from its algorithms, some of which I still use today - thank you ;-) )

    2. Re:What a wonderful project! by Jamie+Lokier · · Score: 3, Interesting

      The bit about my own history was just to illustrate that young people (the target audience for RP apparently) do take an interest in that sort of thing, not to suggest a method! Of course nobody would use that approach any more! (The Elite reference was because David Braben co-authored Elite and is also involved in RP).

      If analysing the blob statically, and if you know the instruction architecture, we have much better tools now, including disassemblers, decompilers, type inference and much more. And internet so we can collaborate better.

      16MB is a big blob, but it's highly unlikely that much of it is needed to make a useful open source subset of the functionality.

      For perspective on speed: Recently I had to reverse engineer about half of a 1.5MB ARM driver blob in some detail, enough to fix bugs and improve performance deep within it. I'm not going to say what it was, only that it took me about 2 weeks with objdump and some scripts, not using more advanced tools. I didn't enjoy it because it was just to fix some bugs the manufacturer left in :-/ (The best bit was a one-bit change that tripled video playback performance and stopped it stuttering :roll-eyes:)

      But there may be a big fat license prohibiting anyone from openly using the results of that type of deep code analysis on the RP's blob.

      Plus, there's the secret GPU/RISC architecture to get to grips with; that's not going to be obvious.

      So it would probably have to be Nouveau-style: Run the original, watch its interactions with the device (with tracing probes), replay things, change things randomly, try things, gradually build up a picture through guessing as much as anything. That's a much bigger task than statically analysing a blob's code. (At least, to me it seems so.) I don't know whether it's practical on the RP, and I don't know whether it's too difficult. But it worked with Nouveau - and that now supports a lot of nVidia chips - so not to be dismissed as impossible.

      You never start all over after a chip rev. That's why they call them revs, not new architectures. You can diff code in blobs if need be; often the changes for a chip rev are very small.

      You may be right about needing a lot of 11-year-olds (or others). Luckily the RP is cheap and interesting enough, that it might attract enough interest.

      The suggestion isn't all that serious, but nor is it an impossible task, so I think it's worth floating the idea around, see how much interest there is in at least looking further at the practicalities and legalities.

  14. Embiggen... by linatux · · Score: 3, Informative

    a perfectly cromulent word

  15. Re:Features? by NixieBunny · · Score: 3, Insightful

    That's what Arduino shields are for.

    It would be rather difficult to make any GHz computer board these days using parts that a person could solder by hand. That's the price we pay for having $100 GHz computers.

    --
    The determined Real Programmer can write Fortran programs in any language.
  16. Re:Amazing by JDG1980 · · Score: 2

    The real question is whether the underlying APIs will be open to the public, or if you'll have to sign some sort of Broadcom NDA to actually use the features the hardware already contains. Also, I'm interested to know if HDMI 1.3 bitstreaming (TrueHD and DTS-HD) is incorporated. These shouldn't require any licenses since the data isn't being decoded, just packetized and sent over a cable.

    *If* the APIs are open, this could be a great XBMC platform with full support for all the Blu-ray codecs.

  17. Re:Repeat much? by kiwimate · · Score: 3

    Y'know...being candid, I'm barely interested in Raspberry Pi at all...but this is definitely of note for the target audience for Slashdot, or what Slashdot used to be in the late 90s when I first started reading it. Much better than some of the really worthless ask slashdot questions that get through, for instance.

  18. What's in a Master Card? by Ostracus · · Score: 2

    With that in mind, they revealed the final board is exactly the same size as a credit card, measuring 85.65 x 53.98mm."

    And it's name will be Selma

    --
    Shai Schticks:"You don't make peace with friends, you make peace with enemies"
  19. Re:Features? by inflex · · Score: 2

    Really, SMD is not hard to solder, you just use different techniques with your old tools.

    Sure, BGA is out of the picture for most people, but SOIC, TQFP, SSOP/MSSOP and parts down to 0402 are still hand-solderable. You just have to make the mental shift away from thinking "OMGZ, It's surface mount, I'll never be able to solder that!". In many ways SMD is a lot easier and simpler, because surface tension becomes your friend.

    Of course, failing that, go get a skillet and some solder-paste or convert a pizza oven into a reflow chamber. I for one am happy to never deal with pin-through again.

  20. Re:How can you even tell? by Savantissimo · · Score: 4, Informative

    Most of those questions are answered in the comment thread on the article. No individual layers released until their PCB designer gets back. The picture shown does not include power or ground planes, so the missing ground is likely hidden. The connectors being used will require some through-hole components. The GPIO headers will be on the final release, but unpopulated.

    The biggest omission to my mind is the lack of mounting holes or other fixtures. (I'm not sure where you see "plenty of empty space". Even getting screw holes to fit would require some thought, it seems to me.) The screenshot was also pretty useless for determining the exact mechanical placement and dimensions of the connectors, which is the only important thing for those designing cases. Someone in the comment thread did mark and label the rough outlines of the connectors, though. The connector placement also seems not at all designed for usability, or with any thought to future case design but purely to make the cheapest possible board.

    --
    "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
  21. Re:Repeat much? by tchuladdiass · · Score: 3, Insightful

    I think the biggest thing that can come out of this project (especially if more like it come around) is the fact that the hardware is too cheap to run a non-free OS on it. Now sure, to make it into a full computer you have to add a monitor, keyboard, mouse, USB hub, storage (not sure if it comes with flash built in or if it needs a SD card to boot from), and and Internet connection. But most people are going to see the $25 price (assuming something like this ever gets retail) and pick one up. The netbooks almost made this happen (since they were Linux only when they first came out -- until Microsoft cut a deal for Windows XP). Only thing is, would the typical user be using a Debian based (or similar) distro, or would they be using a version of Android?

    The only thing I think that would make this more useful is if they added another, say, $30 or so to the price and added a calculator screen / keypad to it (and battery/charging circuitry). Since most high school kids need a $100 graphing calculator, one that transforms into full workstation when plugged into a monitor/keyboard would be great. Of course the schools probably would never allow the use of an "open" calculator on exams (but then again, most high school level exams only need a simple scientific calculator -- or a slide rule).

  22. Re:Repeat much? by mollymoo · · Score: 3, Interesting

    You talk as though the Pi is feeble. It's a staggeringly powerful computer. Better than a workstation of a few years ago or a supercomputer of a few decades ago. You know, the kinds of things they used to design jet aircraft, run accounts for multi-national corporations, invent nuclear weapons, plan space missions, develop models of the universe and stuff. We're just accustomed to almost unbelievably powerful computers.

    If you want someone to learn how to code efficiently give them an 8-bit microcontroller, not a 32-bit one-point-something GHz CPU with hundreds of MB of RAM.

    --
    Chernobyl 'not a wildlife haven' - BBC News
  23. Re:Repeat much? by Yvan256 · · Score: 2

    Pick up an AVR and code in C. Not even an ATmega, start with an ATtiny. And to push things even further, I would suggest the ATtiny85 instead of the ATtiny861.

  24. Re:Features? by mangu · · Score: 2

    Why not?

    Because, except for hobby or training, it doesn't make sense.

    There was a time when one used lots of 555 chips. Today you have the 12F675 PIC in the same eight pin format that can do almost everything the 555 can do without any external components. A 12F675 cost about $1.60, which is $1 over the price of a 555, but the lack of external components and the added flexibility will compensate for that.

    The same can be said of most discrete logic chips. Unless it's a very simple logic function, it makes more sense to use a PIC than to assemble a circuit from TTL or CMOS chips.

  25. Re:Repeat much? by hairyfeet · · Score: 2

    Did you even READ the post I was responding to? The guy was so desperate for Linux to gain ANY share he cooked up this scenario where a $25 cell phone GPU caused a "revolution" with people buying this en masse and tossing Windows! Nobody and I repeat NOBODY that uses a modern or even older Windows desktop/netbook/laptop is gonna shitcan their current setup for a $25 cell phone GPU that doesn't even come in a case!

    You wanna know why Linux numbers are flatline? Its actually really simple, its because the developers and community won't listen and violate rule 1 of business, give the people what they want or at least what they think they want! Instead to paraphrase a line from Vietnam the whole thing has been taken over by deluded zealots that truly believe 'inside every user is a C programmer waiting to get out' like Suzy the checkout girl is reading Bash programming manuals in the bathtub and grandma is working on her CS degree in between knitting classes, its fucking nuts!

    Look, if you want to be a hobbyist OS for programmers? I have NOTHING against that, in fact I ran OS/2 for years after everyone else had bailed. But coming up with one delusional scenario after another just makes your OS look like the property of the "Elvis is alive, NASA faked the moon landing" tinfoil hat wearing nutters. When I am having a conversation with a 15+ year Linux server admin who runs a giant server farm for a living and they tell me when i ask what distro to try as a final gasp before giving up and they say "As soon as I'm backed up i'm going to FreeBSD and if that doesn't cut the mustard I'm giving up on FOSS desktops and going Mac or Windows" you KNOW the shit is fucked up.

    Fix the driver borkage (Protip: everyone else from BSD to Solaris has had a hardware ABI for nearly a decade, you think you are smarter than every OS designer on the planet?) and make an OS that will pass my "Is it safe?" test, where I simulate a user having the machine for 3 years by downloading the distro from 3 years ago and updating to current (which of course causes it to fall down like a house of cards) and then we'll talk. Keep predicting that some niche device will magically make people see bash prompts and programming as "the next big thing" and we'll all laugh at you and you'll stay flatline, kinda like...well right now actually. Kinda sad when MSFT puts out Vista, one of the most hated of their OSes EVAR, and you can't even gain a single percentage point. that is just sad man, totally sad and pathetic.

    --
    ACs don't waste your time replying, your posts are never seen by me.