1 3 4 5 6 7 188 Replies Latest reply on Jul 21, 2012 4:04 AM by puddle1944 Go to original post Branched to a new discussion.
      • 60. Re: Raspberry Pi - Hardware Flaws and Fixups?

        actually, the design may not be quite final yet.  Liz said: "Happily, we’ve found it doesn’t need a shielded enclosure to reach Class B, although it will require a (very minimal) redesign." http://www.raspberrypi.org/archives/978, page 3, April 10, 2012 at 7:04 pm.


        It hasn't been announced when such a change might be implemented, but probably better sooner rather than later, given the large production runs planned, perhaps along with a change to fix the SD card voltage issue.

        • 61. Re: Raspberry Pi - Hardware Flaws and Fixups?

          Sure, future batches are likely to differ a bit, but the boards that customers are receiving right now are not going to change.  The boards that are already in people's hands require a schematic.

          • 62. Re: Raspberry Pi - Hardware Flaws and Fixups?

            Did Liz not also clarify that the small change to be made was a software one, to reduce the drive level of the HDMI output?

            • 63. Re: Raspberry Pi - Hardware Flaws and Fixups?

              Morgaine, what could you possibly do with a schematic of this device?


              I think that when you get one you will find that the ultra fine pitch, and, multiple (wasn't it 6?) layer board, the fact that the memory to SoC connection is under the RAM and the SoC to board connection is under the SoC, you're not going to be able to do what you imagine.


              There really aren't that many parts here and they are connected "in the obvious way."

              Plug --> polyfuse --> 5V line --> 3.3v reg --> lv reg --> SoC

              SoC --> USB chip --> Ethernet chip

              • 64. Re: Raspberry Pi - Hardware Flaws and Fixups?


                  It's a bit confusing because there are 2 separate changes needed.

                The software (gpu blob) change for the HDMI that you mention was needed

                for Class A certification.   A completely separate hardware redesign change

                was found to be needed for Class B certification as Liz described in the

                linked forum.   Since there obviously wasn't time to make the hardware change,

                only Class A certification was obtained.


                We haven't been told exactly what the hardware change involves, or when it

                will be implemented.  Maybe PeteL can enlighten us soon.

                • 65. Re: Raspberry Pi - Hardware Flaws and Fixups?


                    There are a variety of reasons for wanting to see a schematic besides wanting

                  to modify a board.  For example, a schematic might be useful for explaining what

                  modification is needed for the Class B issue Liz mentioned above, or for explaining

                  what modifications might be needed to get I2S functionality back..

                  • 66. Re: Raspberry Pi - Hardware Flaws and Fixups?
                    Roger Wolff

                    I'm the proud owner of a 'pi.

                    Broadcom has released the "Arm peripherals" datasheet of the BCM2835 chip. First things first, I wanted to see something from the UART. So I search the data sheet for UART and find that there are three uarts, two different designs. The pins connected to the GPIO are labeled: "UART RX" and "UART TX" not "UART 2 TX". Which one is it?

                    Turns out I was able to figure it out without crashing my 'pi. Good!


                    However next in line is my I2C interface. This too is labeled on the GPIO port as: I2C SDA, I2C SCL, and I'll have to guess which of the several I2C interfaces is connected to the GPIO pins and that by attempting to send a byte there I don't crash or break things if I happen to pick the wrong one....


                    These are things that a schematic tells you.


                    Similarly, a schematic can answer questions like:

                    • If I want to power my 'PI, can I do so from the 5V pin on the GPIO port?
                    • What will happen if I want to save power and directly provide 3.3V on the GPIO port? (*)
                    • In that case, should I leave teh 5V floating, short it to 3.3V, or provide a diode between 3.3V and 5V?


                    Those are just the questions that I have come across on my first day of owning a raspberry pi that a schematic would have answered.


                    (*) eventually I might install a RPI in my car. Maybe it will stay on 24/7. In that case saving power is important, to prevent draining the starter battery. A 12V->3.3V switching powersupply will do better than a 12V->5V switcher and then letting the linear converter on the board do the 3.3V conversion.

                    • 67. Re: Raspberry Pi - Hardware Flaws and Fixups?
                      Roger Wolff

                      PeteL, are you still reading this thread?


                      You mentioned using a high quality micro USB connector with through-hole pins.


                      It seems the chinese were able to substitute a cheaper component for the microUSB. I don't seen any through-holes on the connector. (the holes are there on the board, but there is no metal sticking through the board!)

                      • 68. Re: Raspberry Pi - Hardware Flaws and Fixups?

                        Roger & all


                        I am - but just got home after a 12 hr flight (family holiday).  Will start to respond to all the issues (including Pins and Schematics) as soon as I'm awake enough to make sensible comments. We are working on mods and I would like to make sure that on any released schematics you have an idea what is vunerable to change.


                        Sorry for the blackout - did post on my e14 status but I don't think it is really visible!





                        • 69. Re: Raspberry Pi - Hardware Flaws and Fixups?

                          Thanks Pete.  But don't bother improving the schematic further before initial release.  The board is already in the hands of customers, so whatever you managed to work from, that'll be good enough as a starting point for those who need it.  Release it as is, as version 1.0.  Subsequent v1.1 etc releases can carry the improvements.


                          "Release early, release often" applies as much to schematics as it does to open source software.  Others will help you improve it, both with suggestions and with actual updates if you're using some standard schematic tool.



                          • 70. Re: Raspberry Pi - Hardware Flaws and Fixups?

                            Hi Roger, long time no see... Still living in Delft and doing I2C kernel activities... ?


                            What I see from the docs at smsc  the lan9512/13/14 are all Compact 9x9mm, RoHS-compliant, 64-pin QFN package

                            price difference what I can find is 0.30 - 0.40  between an lan9512 and lan9514

                            It is only an option if they are thinking about a redesign of the pcb... (probably not). since you also need space for a connector..


                            • 71. Re: Raspberry Pi - Hardware Flaws and Fixups?

                              Pete: great to hear you are back from a well-earned vacation! Hope to hear more soon once you've rested up from the trip. 


                              I think as long as the date and the version are clearly marked on the schematic, that's all you should need to do for now.  A "wish list" for the next board spin is fine, but not as high a priority for those of us on the outside just now, in my opinion.


                              As you'll see from the RasPi forums, seems like a lot of issues which may be related to cheap USB cables having high resistance (would you believe up to 4 ohms? that would drop your 5V down to 3V, at 500 mA). Also a lot of SD card questions which in some cases have been pilot error (incorrect use of 'dd' utility) and sometimes apparently incompatible cards. And if the below claim is true, it certainly doesn't help finding a reliable card:


                              • 72. Re: Raspberry Pi - Hardware Flaws and Fixups?
                                Roger Wolff

                                Hi Hans, Yes still living in Delft. Yes I'm working on I2C / SPI right now, but have I done that before? Hmm.


                                Anway, looking at the chip on my RPI, I noticed that it had 64 pins instead of the 48 I was expecting. I apparently misread the datasheet. Happens every now and then. :-(


                                Re: SD cards:  I have a 4G kingston card, which apparently locks up every now and then. Things stop for 5 seconds and then get going again (the kernel prints something about a timeout).

                                I'm hoping that the fix by Russel King for this works.



                                R34, the current limiting resistor for the power Led, is too small. It hurts my eyes. In the old days you'd use something like 220 or 330 ohms. Nowadays you'd take say 1k. (which it probably is). I decided to go for 10k on one of my designs, but didn't realize that there were 15k resistors in my storage box labeled 10k (which is short for 10-20k), So I soldered on 15k, and I like that....


                                Pete, are these resistors 0402 or 0603? I'll measure when I get a chance. Maybe I'll swap it out one day if it irritates me enough.... But most likely not before I can manage to have a spare RPI on hand.


                                The one on the yellow led has the same problem, but not as dramatic. 2k2 or 3k3 would do if it is now 1k.

                                • 73. Re: Raspberry Pi - Hardware Flaws and Fixups?

                                  Hi  All


                                  Schematics - Yes we have had a discussion on this and there are a set in the release pipe and they reflect the current status of the delivered boards as of today.  Will post back here as soon as they are ready for download on the raspberrypi main site ( I know Liz and Eben are still running round like mad things).


                                  The Pi board has a set of 4 hard links that can be read by the firmware so it knows which version of the board it has and can configure accordingly.  However, anyone who is doing something more than just software needs to know what may change (e.g. GPIO) so they can plan for it. We have a candidate list and this will be published soon but now separately from schematics.


                                  Bright LEDs - They are, we will look at dimming them down but some people who are designing cases want to use light pipes of some sort and this makes them harder to see if they are not 'bright'.  Guess we could save some power?


                                  Cables - we have not seen a problem with any of the ones we have been using - or reports from developers, BUT now we have a population of more than a few hundred I can see issues like this appearing.  We just need to work together to pass around knowledge.


                                  More later - need to dash.



                                  • 74. Re: Raspberry Pi - Hardware Flaws and Fixups?


                                      That's an interesting observation that the micro USB connector may have been

                                    substituted for a cheaper surface-mount one.  Paul Maunders, with beta board #8,

                                    commented on how rugged the power connector felt:


                                    but GizmoB73, with a production road-test unit commented just the opposite.

                                    Now that apparent conflict makes sense.


                                    After the ethernet jack issue, it makes you wonder if any other substitutions were made.

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