Featured Articles
Announcing Pi
Technical Specifications
Raspberry Pi FAQs
Win a Pi
Raspberry Pi Wishlist
Actions
Forum Thread Details
  • Replies 231 replies
  • Subscribers 669 subscribers
  • Views 26606 views
  • Users 0 members are here
Related

RG1 1.8v regulator

Former Member

Ok, so in a different thread I threatened to remove RG1 and do some current measurements on it's output after seeing those thermal images that show it's not generating any heat...

 

Well, I did it tonight. Some photos here: https://picasaweb.google.com/selsinork/RPi18v

 

The jumper pins in the output let me either just put a jumper on and verify the Pi boots ok, or wire a multimeter in series to get some current readings.

 

The results were interesting to say the least. I had to go back and check I was reading the multimeter correctly, that it wasn't broken etc.

 

On initial power up I see a negative current for a second or so which then reverses to about 0.5mA (yes half a milliamp, that's not a typo) for a few seconds while we get the first sd-card accesses. Once we're booted and sitting at the login prompt the current reading fluctuates from around 0.001mA to maybe 0.04mA. 

 

I'm using the 40mA range on a decent Fluke multimeter, so I've no reason to doubt the results. There's obviously going to be some inaccuracy down at that level due to length of meter leads etc, but the result is fairly clear.  You'll understand why I was checking the meter was working and I was reading it correctly though image

 

 

So from there onto the next test, lets try completely disconnecting RG1 and see if the Pi boots while using the LAN9512 1.8v 'output'.  Yes it does! 

 

I think that's reasonably good indication that jamodio got it spot on, the lan9512 shouldn't be connected to the 1.8v plane and it's heat problems are going to be largely due to supplying current on it's 1.8v filter pin that it was never designed to do.

 

So anyone willing to pull RG1 off a Pi and verify my results ?

Parents

  • Time keeps going by and I don't see any information being shared by Pete or anybody from RPF about the issues and what we can expect to get them fixed.

     

    -J

  • in reply to jamodio

    Jamodio,

      right, Pete has gone silent, and JamesH says he can't say much.

    Pete said he was in full-duplex communication with SMSC, but

    apparently he's not eager to share.

     

    People have asked for gerbers to see if there's a way to disconnect

    1.8v by drilling a hole in a strategic place, but no response.

     

    That doesn't mean progress isn't being made, such as people

    experimenting with heatsinks.   Maybe SMSC could be asked

    if the networking problems are a plausible result.  Maybe someone

    will use sandpaper to reveal exactly how the power is connected.

  • in reply to Former Member

    coder27 wrote:

     

    People have asked for gerbers to see if there's a way to disconnect

    1.8v by drilling a hole in a strategic place, but no response.

     

    I've seen people ask for gerbers just for openness on principle, but not for that specific diagnostic purpose.

     

    If that request was made in a place which RPF could not have missed, and they responded with silence, it's worse than I thought.  They don't even value help from their dedicated supporters.

     

    The Foundation is rapidly losing all the little credibility that's left.  What a bunch of self-centered and myopic incompetents.

  • in reply to Former Member

    Guys, everybody is blaming the 1.8V problem for the keyboard repeat problems. However, the source of the keyboard repeats has been found, and it is that USB interrupts are delayed more than 1ms. The cause for this is the SD card driver. That is why morgaine is now using an USB stick for his root.

     

    The kernel/sd card driver will be fixed in time. In parallel other people can fix the 1.8V problem, but I haven't seen a confirmed problem caused by this.

     

    The 0.15W extra power in the LAN chip will raise the temperature of the LAN chip by a few degrees. Maybe 10. This should be within range of what is allowable.

     

    Diagnosing "intermittent" problems is difficult. people see patterns way too quickly. You have to try with and without a few times and reproduce the problem consistently with one setup and not with the other.

  • in reply to rew

    Roger,

      I don't think the keyboard repeats problem is quite so well understood.

    User Max still reports problems with the Enter key.

     

    http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=12097&start=241

     

    If SMSC is telling Pete not to worry about the LAN chip, then he would

    probably be eager to share that. 

  • in reply to Former Member

    Coder, SMSC is NOT telling pete not to worry. Someone else asked SMSC and got told: "No way!".

     

    In some "circles", the understanding is that oscilations will result if you parallel two linear regulators. This is not always true. In many linear regulator datasheets they recommend the parallel setup for situations where you need up to 2x the current of just one of the regulators.

     

    With Pete's preoccupation with "sufficient decoupling", this means that I really don't expect any oscilations.

     

    SMSC says the regulator should not provide external current. Fine. But what happens if you do draw current? You might cause the SMSC regulator to drop into the "dropout" region. So it will be in "constant current" mode. So regulation is delgated to the RG1 regulator. Still the voltage will remain within tolerance.

     

    This means that the only problem is that 0.15W is dissipated in the SMSC chip, instead of the RG1. As said before.

     

    With "intermittend problems", and interrupt problems not completely fixed, I'm not too worried about the single report that mentions an enter-keyup event going missing.

  • in reply to rew

    I don't agree that everybody is blaming the 1.8V problem to keyboard repeats or anything else related to USB, at least I don't.

     

    That's is simply a clear and flat error that needs to be fixed, again we can theorize and overanalyze the potential side effects of the error but it does not fix it and there are so many variables and other issues that make things not work for some folks and work for others.

     

    I don't believe much that the USB problems are related to this one, I'd lean more in the direction that we are trying to squeeze a full featured USB host from a flaky USB OTG not very well known and coded on the drivers implementation.

     

    -J

  • in reply to rew

    It is not clear who is telling who what, but what is pretty clear is that we are not being told anything !!

     

    I strongly believe that at this instance the distributors should stop producing and selling the current revision of the board, which is clearly faulty.

     

    -J

  • in reply to jamodio

    Flaky? I have the impression that the hardware is not flaky. Its just that the hardware is a bit minimal. It defers to software all that CAN be deferred to software. Together with the minimal documentation, and interactions with other Linux drivers, it turns out that it's not quite finished yet.

     

    ... stop selling ... faulty.....

     

    They clearly should continue selling the boards, which "work for  me".

    With a $1 heatsink on the lan chip you can (over) compensate for the extra heat if you want.

     

    Part of "getting this software problem fixed" is in getting enough devices out in the field so that some brilliant linux-hacker gets one and says: Oh, this is a simple problem to fix, and fixes the driver-problem. The original plan was to get 10k units out to just Linux-hackers. But how do you restrict access to the people you want? Impossible. The only way is to flood the market, and hope the right people obtain one.

  • in reply to rew

    From a power supply design is both flaky and faulty, from a user perspective is flaky and unreliable.

     

    I've a heathsink on both the SoC and SMSC and that does not fix the problems with USB.

     

    When I found and detected the 1V8 problem I didn't have a R-Pi board in my hands, the error was just clearly visible in the schematics.

     

    We already know that the "original plan" was badly exectued by the RPF folks, they didn't listen before, during and after the launch, and they continue on that behavior.

     

    Flooding the market with a faulty product is not a reasonable and measurable approach to fix problems and improve hardware/firmware, putting the boards on the right hands would have been more effective, hope is not a very reliable tool of engineering.

     

    I said it many times already, I'm not a fanboi but neither a detractor of the R-Pi, I still consider it a good idea, something worth to have, but it needs to get FIXED !!

     

    -J

Reply
  • in reply to rew

    From a power supply design is both flaky and faulty, from a user perspective is flaky and unreliable.

     

    I've a heathsink on both the SoC and SMSC and that does not fix the problems with USB.

     

    When I found and detected the 1V8 problem I didn't have a R-Pi board in my hands, the error was just clearly visible in the schematics.

     

    We already know that the "original plan" was badly exectued by the RPF folks, they didn't listen before, during and after the launch, and they continue on that behavior.

     

    Flooding the market with a faulty product is not a reasonable and measurable approach to fix problems and improve hardware/firmware, putting the boards on the right hands would have been more effective, hope is not a very reliable tool of engineering.

     

    I said it many times already, I'm not a fanboi but neither a detractor of the R-Pi, I still consider it a good idea, something worth to have, but it needs to get FIXED !!

     

    -J

Children
No Data