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  • 90. Re: Raspberry Pi - Hardware Flaws and Fixups?
    CJE-Micros-4D Level 1

    Thanks for all the info Pete. A summary of possible 'minor' hardware changes that I've spotted in the forums:

     

    1. I2S implement  as per the data sheet

     

    2. SD card voltage option bank change, as per Dom's posting in: http://www.raspberrypi.org/forum/general-discussion/where-is-the-bottleneck#p62401

     

    3. USB OTG Id Pin to spare GPIO pin (effective only on Model A) as per:

    http://www.raspberrypi.org/forum/features-and-requests/cheap-but-crucial-model-a-feature-request-read-this?value=gpio%20usb%20pin%20request&type=2&include=1&search=1&ret=all

     

    I'm not sure if the next two are technically possible!

     

    4. Assisting POE (spare wires variant) adaptors exist that inject power onto the unused lines of ethernet and then split them out again after a cable

    run see: http://www.cjemicros.co.uk/micros/individual/newprodpages/prodinfo.php?prodcode=4D-RPI-POE-IS-C (The Raspberry Pi adaptor cables doubles the price!) but if R-Pi's RJ45 could be changed for a variant that took the extra lines Earth to R-Pi's Earth and the Injected Power lines to R-Pi 5V via a link.

     

    Pros: simple for end users to setup and injector only cable should be cheap.

    Cons: POE variant of RJ45 with magnetics needed [1], cost, Reduced Isolation and extra link needed.

     

    5. Assisting POE (via GPIO daughter board) If a POE daughter board was plugged into the GPIO pins with the daughter board having a POE input

    RJ45 on it, supplying power to the R-Pi. The four ethernet data line output from the daughter board being connected to currently unused GPIO pins. I suspect inputting ethernet via the GPIO pins breaks various rules and could add to RF output:-(

    Original suggestion at: http://www.raspberrypi.org/forum/features-and-requests/routing-ethernet-pins-4578-to-the-expansion-port

     

    [1] I found a mag jack that might the type needed at: http://www.adam-tech.com/catalog/2012/page_009-049.pdf

    See page 37 of 41 (marked Page 45) layout M16

     

    n.b. I'm intrigued, what do the two diodes on the underside near the USB sockets protect?

    I'd thought the USB ports, but people have mentioned on the forums that they have (unreliably) powered R-Pis via one of the two USB ports.

  • 91. Re: Raspberry Pi - Hardware Flaws and Fixups?
    piovrauze New Members

    mmm, I really hope those "power issues" turn out to be just bad cable/adaptors/ppl doing it wrong.

    You guys are working on it I suppose.

    btw PeteL, what is requiring redesign (for full compliance)? That's what is bugging me, since it leads to another question: when will this be implemented (and then re-certified)? Before or after the queue of orders?

    I guess "what are the changes needed" is more your cup of coffee (or better tea), so that's what I'd really like you to enlight me on.

     

    Btw, is it just me or those 2k units feel a lot like a pre-serie?

  • 92. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Roger Wolff Level 7

    "those 2K" should be "those 10k". The other 8k are Guaranteed to be exactly the same: they were produced feb-march just like the first 2k that are delivered right now.

     

    and yes, I too would want to know what changes seem to be neccessary and when they will go through.

     

    What is the HD interface? (schematics P4 left top)

     

    What value is typical for the built-in pullup/pulldown? I expect that to be on the order of 50-100k. In that case you can encode 3^4 different board revisions with the 4 board-revision strap resistors:

    read value. If zero, enable pullup, if one enable pulldown. If value now changes, the strap is left "open", so that's the third value.  (Ah! found them!).

     

    There is an error in the schematics. p3 mentions the "USB" part of the LAN9512 as "model A only". That should be "Model B only" of course.

     

    R22-R25, R28, C28 are missing their "Model B only" tag.

     

    Why is there a line going from R25 to R22?

     

    Due to space constraints the 100M led is labeled 10M on the board. How about calling that "FE" for "Fast Ethernet"? That's what 100M was called back in the days.

     

    On the other hand, I would much rather have a BCM2835 GPIO pin control a led in that position. If we want, we can program it for the 100M/FE function in software, but it provides those who are going "bare bones" with an extra debugging option.

     

    Similarly, the FDX led is nowadays a bit outdated. Why on earth are we still interested in that statusbit? Any reasonably recent setup will run full duplex, and it won't help in debugging in seeing that led remain off. Again: A gpio LED would be a nice replacement. The easiest way to notice a halff duplex link is to watch "dmesg": smsc95xx 1-1.1:1.0: eth0: link up, 100Mbps, full-duplex, lpa 0xC5E1

     

     

    What is the purpose of D15, D16? I'm thinking: Protection against static discharges, right? The question is: Wouldn't it be better to connect their kathode to +5V0 instead of +5V0_HDMI? The +5V_HDMI is just a small net that only has the 100N C75 on it....

     

    Are the HDMI_SDA and HDMI_SCL pins 5V tolerant? I wouldn't have guessed.

  • 93. Re: Raspberry Pi - Hardware Flaws and Fixups?
    PeteL Level 3

    Just in case you missed it, I did - tied up in a meeting, Liz has posted the schematics on the main site.

     

    I'll let everyone have their comments and inputs and review/respond in detail where I can in few days.

     

    I will also start a new discussion here, PLEASE put all comments on the schema's there, and the folks who have already please cross post, it keeps it all nicely together and will be useful for people to read.

     

    Cheers

     

    Pete

  • 94. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Roger Wolff Level 7

    Pete, I was just checking my 5V power, and found that with the Raspberry powered off, there was still about 1.3V on the 5V0 line. Removing cables one by one indicated this was coming from HDMI.

     

    Turns out 5V0_HDMI is 2.7V. and the HDMI_SCL and HDMI_SDA are 3.something.

     

    So apparently my IIYAMA monitor is partially powering the RASPI through the I2C datalines....

     

    Why not use a BAV99S (from NXP) for D15 AND D16 (i.e. use the 6 pin, 4 diode version).

    Same goes for D12, D13. And possibly D4 and D14. (but those are annoyingly far apart I guess).

  • 95. Re: Raspberry Pi - Hardware Flaws and Fixups?
    HansH New Members

    On the other hand, I would much rather have a BCM2835 GPIO pin control a led in that position. If we want, we can program it for the 100M/FE function in software, but it provides those who are going "bare bones" with an extra debugging option.

     

    Similarly, the FDX led is nowadays a bit outdated. Why on earth are we still interested in that statusbit? Any reasonably recent setup will run full duplex, and it won't help in debugging in seeing that led remain off. Again: A gpio LED would be a nice replacement. The easiest way to notice a halff duplex link is to watch "dmesg": smsc95xx 1-1.1:1.0: eth0: link up, 100Mbps,full-duplex, lpa 0xC5E1

     

    I agree with that, FDX led is not really usefull, it would be much better if that could be used as a gpio led.

    That way you can directly let kids program the led without the need for extra hardware.

    Hans

     


    Raspberry Pi forum :  custom cases
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  • 96. Re: Raspberry Pi - Hardware Flaws and Fixups?
    John Beetem Level 15

    Well, in principle you can use the FDX as a GPIO LED.  The difficulty is that you need to talk to the LAN9512 in USB-speak to configure and toggle it, and the driver may make this difficult.  Still, students would learn a lot about USB drivers trying to do it :-)

  • 97. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Roger Wolff Level 7

    Was it here that someone asked me to measure the physical size of the 'pi? Mine is 55.9 x 84.9mm.

  • 98. Re: Raspberry Pi - Hardware Flaws and Fixups?
    HansH New Members

    Yes me...  thx Roger.

     

    Hans

     


    Raspberry Pi forum :  custom cases
    Shapeways: picases
    Thingiverse : 3D printer case
    Thingiverse :Pi Lego blocks
  • 99. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Montala Level 1

    I know it is only slightly different, and may not matter at all, but in a post on the Raspberrypi.org website one recipient (another case manufacturer actually) has said that: The board is 85.00 x 56.17


  • 100. Re: Raspberry Pi - Hardware Flaws and Fixups?
    KenT New Members

    Pete. Very excited, I've been looking for the Raspberry Pi for the last two years to make an affordable audio player to generate sound effects and audio interpretation for museum exhibits. The aim would be to trigger the audio with a PIR via the GPIO. There would be no display so I need to use the 2.5mm audio jack. In this thread http://www.raspberrypi.org/forum/features-and-requests/possible-higher-bitrate-dac-in-the-future item  6 GERT mentions that there will be power supply noise on the audio. I don't have a Pi yet so don't know what this sounds like but for amplified sound effects background noise is important. I wonder if the situation can be improved in the next revision, or maybe the pwm lines brought out to the GPIO connector so users can implement their own clean power supply, driver and filter as described in the same thread. The GPIO solution would give 2 additional pwm outputs, assuming they can be decoupled from the audio software.

    Regards

    Ken Thompson

  • 101. Re: Raspberry Pi - Hardware Flaws and Fixups?
    HansH New Members

    Hi David, yes I know   ModMyPi measured that....  That is why I asked Roger... I know he is very precise...

    So probably the pcb board is 85.0 x 56.0  with 0.2 tolerance

    All my cases are made 85.6 x 56.0, and I have 4 lying here waiting.... but I was not that lucky in getting a Pi...

    So the pcb will fit,  even if it is .17 wider I can probably shave a little off the pcb board...

     

    Hans

     


    Raspberry Pi forum :  custom cases
    Shapeways: picases
    Thingiverse : 3D printer case
    Thingiverse :Pi Lego blocks
  • 102. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Level 15

    The schematic doesn't appear to show the memory chip-select lines,

    but Gert has mentioned that the SoC has only a single chip-select line,

    which prevents stacking more than one memory chip, as described here:

    http://www.engadget.com/2011/03/25/samsung-starts-baking-30nm-4gb-lpddr2-chips-packaging-2gb-mobil/

     

    Are the production volumes large enough now that Broadcom might consider

    presumably minor changes such as adding an additional chip-select line?

  • 103. Re: Raspberry Pi - Hardware Flaws and Fixups?
    PeteL Level 3

    The schematic does not show any of the connections to the Package on Package (POP) memory that actually sits on top of the BCM2835.  It never gets to the PCB so there is just a hidden attribute that calls up the part onto the parts list so it doesn't get forgotten!  I think I should make reference to that on the next schematic set.

     

    More than one chip select would not be of any use unless a memory manufacturer decided to make a DRAM chip that passed through all the signals (and the additional chip select) to a package that sits above.

     

    Theoretically it is possible, and there are examples of Package on Package on Package.  It's not uncommon for this to be done inside a single package (stacked die) but the interconnect is done usually with bond wires.

     

    Unless we pass the 4-5 Million Pi's mark with no obvious tailing off of demand I think Broadcom would not be interested, I suspect the number is in reality much higher than this.  Making even a minor mod to silicon can cost millions of dollars.  One of the big costs used to be a mask set, but now I think direct imaging has taken this out of the loop. I'm sure there are people on the forum who could comment better than me - I just use the chips now. 

     

    I used to make silicon but the advent of cheap (relatively) programmable logic (FPGAs)  has largely chopped away the mid volume market.  The stress of waiting for a PCB spin is nothing compared to 'first off' silicon - hats off to those guys, I'm to old to suffer that now!  You can fix a multitude of sins in an FPGA.

     

    One option discussed before is to use a larger capacity POP memory chip but for the moment this is not in the roadmap.

     

    Cheers

     

    Pete

  • 104. Re: Raspberry Pi - Hardware Flaws and Fixups?
    Level 15

    The engadget article I cited mentions getting 1GB by stacking 2 4Gb memory chips,

    where otherwise stacking 4 2Gb chips would be required.  I'm not sure if that involves

    multiple chip-select lines or not.  I'm also not certain what memory parts are actually

    available since this article.

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