RG1 1.8v regulator

As shown in Troy Mackay's post on Jul 28 it seems to me that we could mod our PI's to work more as the chips were designed.

I think that this could make the PI more stable, from the looks of it.

I am not a designer Just an old tech, but I think we need to find a way to FIX what we now know is an error in the board.

So could someone do some practical testing to see if there is something that can be done to easly fix the current board, rather than wait for RPI foundation to fix it by waiting for a board redesign?

i will love to try out the hack Troy mackay has done also and then test again with that fix on the board, but i have looked into this and i most say it is very well done by Troy as i think it is to small for me todo and i done have an microscope as need for this.

so yes if some one can findout where to make an cut to split the LAN9512 1v8 from the lod 1v8 then i will try this also.

Tooms

selsinork wrote:

 

It's also highly likely they'll have some sort of records retention policy to make sure anything that could potentially be requested for a court case gets deleted ASAP.

When I hear the phrase "records retention policy", I immediately think of this Dilbert: http://dilbert.com/strips/comic/2004-03-22/.  I expect that arbitrarily-imposed records retention policies, especially automatic deletion of old e-mail, will result in some large firms collapsing as vital information is no longer available.  However, this will help small firms who have the luxury (and necessity) of being sensible.

selsinork wrote:

 

It might be nice to live in an ideal world where everything was done properly, the world we actually live in is more about protecting IP and maximising shareholder profit. In the eyes of the business people that means something completely different to what the engineers want.

I completely agree with selsinork's comments above, but I'd like to point out to semiconductor manufacturers, their lawyers, and their bean counters that the way to maximize shareholder profit is to sell as many chips as possible, and withholding documentation means that engineers cannot include your chips in their products, or if they do, it will be ever so much harder to get those products working because of a lack of information.  You will not get any revenue from products that fail because good software could not be developed in time because of a lack of documentation.  If you're worried about lawsuits, tell your politicians to change the laws so that you can spend your revenue on product design instead of lawsuits.  Politicians will listen to you because you have deep pockets.

There are several reasons to keep documentation hidden:

• Keep track of who has documentation, so that you can notify them when an "erratum" is found.
• Keep the documentation from view from competitors. Knowing the exact "API" eases copying.
• Keep track who wants to implement things with your chip. It might be useful to send a salesguy over when <somebigcompany> is considering using your chip. (which you know because they requested the docs for that chip).

And when you can't find docs for a chip that you want to use in your hobby project, you have to realize that selling ONE more chip is not what they are after. Even if you manage to convince 9 of 99  friends to duplicate your project.

I'm not saying that I agree with these things, but knowing WHY they might have these policies helps in finding strategies to change them.

jamodio wrote:

 

You can theorize and overanalyze what should happen if you put some extra load on those pins, well, if a car wasn't designed to fly, don't insist making it fly...

+1

There's a reason why engineers devise circuit blocks like LDOs, both conceptual and implemented, and the reason is so that you can black-box functionality and hence ride on the shoulders of giants, instead of crawling along on the ground reinventing everything.  If you break a black box, the giant evaporates and you land on your ass.

Connecting two LDOs in parallel has that effect.  All bets are off.

Fortunately, it doesn't need discussing, as Pete acknowledges the issue.  The only question is what happens now.  As usual RPF is completely opaque on that.

Morgaine.

There are several reasons to keep documentation hidden:

• Part of the design isn't yours and you simply don't have the rights to release any docs.

As a couple of others have commented, various bits probably got bought-in or imported from a design library. So you may not have the docs or may be contractually bound not to disclose them. I'd take a guess that there's all sorts of stuff like that for the reasons Morgaine mentions - and it all comes back to money. Why employ an engineer who understands the inner workings of an LDO when you can simply buy in a cheap design pattern with no knowledge required.

It's not like I'm any different, I'll happily use a chip when I have no real idea how it works as long as there's just enough docs to let me accomplish my goal.

Using black boxes is good, not bad!  Without it we'd still be scratching on cave walls instead of landing 1-ton rovers on Mars.  But those black boxes must be respected, and not compromized by using them out-of-spec.

The giants can evaporate very easily.

The giants can evaporate very easily.

Yes, and that's a risk that never seems to get factored in.  Sooner or later the original designers of the black box have left the company, died, and the knowledge has been lost.

What's then the cost to re-engineer that black box from zero when other reasons demand a change of spec ?

selsinork wrote:

 

The giants can evaporate very easily.

Yes, and that's a risk that never seems to get factored in.  Sooner or later the original designers of the black box have left the company, died, and the knowledge has been lost.

The answer is very simple, yet it is almost always dismissed out of hand by those who look only inwards and lack a global perspective:

Mankind's advances need to be fully open, so that nothing is lost.  Period.

The amount of wasted effort today is just beyond comprehension, as people compete instead of cooperate.  I don't know how one could even begin to quantify the waste, but I very much doubt that more than 1% of Mankind's effort is retained over time and leads to the advance of civilization.  More likely it's 0.001%.  Certainly the vast bulk of all commercial software effort is totally lost to humanity, all those millions of man-years down the drain as soon as software is EOL'd.

It's very sad when you sit back and think about it philosophically.  Technical progress could be running thousands or millions of times as fast as it is today if the fruits of all effort were open rather than zealously protected and then lost.  It's scary to think where we would be today.

Morgaine.

Morgaine Dinova wrote:

 

The amount of wasted effort today is just beyond comprehension, as people compete instead of cooperate.  I don't know how one could even begin to quantify the waste, but I very much doubt that more than 1% of Mankind's effort is retained over time and leads to the advance of civilization.  More likely it's 0.001%.  Certainly the vast bulk of all commercial software effort is totally lost to humanity, all those millions of man-years down the drain as soon as software is EOL'd.

 

It's very sad when you sit back and think about it philosophically.  Technical progress could be running thousands or millions of times as fast as it is today if the fruits of all effort were open rather than zealously protected and then lost.  It's scary to think where we would be today.

OTOH, philosophical progress must keep up with technological progress or mankind can build the tools to destroy itself without developing the wisdom to avoid doing so.  We seem to have dodged the bullet (for now) regarding nuclear self-annihilation, but climate change could easily do the job instead.

John Beetem wrote:

 

developing the wisdom

Not a chance, if you're referring to humans.  It hasn't happened over the few millennia of what we recognize as "civilization", and there's no sign of any change whatsoever now.

It's only our technological capability that progresses, not Homo sapiens itself --- natural evolution is simply not fast enough.  The only way the leading species on the planet will "develop the wisdom" is by integrating with our machinery and in due course leaving Homo Sapiens and its self-destructive grey matter behind.

That possibility is pure speculation, alas.  There is no guarantee that our mental activity can be integrated with machinery even with full control of everything down to atomic level, so the future may unfortunately be either/or, rather than a slow evolution from our unwise past into a logical future.

Morgaine.

There's a report today of a guy who thinks there is a correlation

between hot chips and ethernet cutting out and keyboard repeats.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=14478

"Mine gets pretty hot. Heat I don't mind, but when it does get hot,

the ethernet cuts out and the keyboard repeats happen more often."

There's a report today of a guy who thinks there is a correlation

between hot chips and ethernet cutting out and keyboard repeats.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=14478

"Mine gets pretty hot. Heat I don't mind, but when it does get hot,

the ethernet cuts out and the keyboard repeats happen more often."

I see that mahjongg has become an apologist now, and doesn't even realize when he's teaching Grandma to suck eggs.  Sad.  I guess the fanboi disease over there is contagious.

The Foundation has already found the reason for dropped USB events.  No further speculation is needed.

I now find it amazing and enterteining to see that the minions resist to accept that there are problems with the R-pi. "Hey there is nothing wrong with the board, you already tested 12 keyboards, why not 13 ?" and why a kid should carry the R-pi on their backpack ? Some of us minions of the RPF carry it on our underware !!

Sigh ....

Meanwhile I see "no list" or any other info being "shared," and it surprises me that there is not a single bit of information on the main blog site.

As the issues become exponential it will start to backfire, I'd stop production and selling until the issues get fixed.

Meanwhile APC is making progress announcing Newegg.com as distributor for US and Canada.

-J

jamodio wrote:

 

Meanwhile I see "no list" or any other info being "shared," and it surprises me that there is not a single bit of information on the main blog site.

That's what the guy Sulge who got banned at the start of the "USB discussions getting a bit heated" thread said.

He got banned for only a week (perhaps a sign that some admins are starting to realized that the emperor has no clothes), so let's see what he says when he comes back and points out that the very problems he was describing were confirmed by the Foundation's engineers.

Meanwhile APC is making progress announcing Newegg.com as distributor for US and Canada.

Excellent, that makes it a lot more likely that a UK distributor will appear before long.  The APC and BeagleBone are the only two cheap boards with Ethernet MAC directly on the SoC instead of attached over USB, so I'm very favourably predisposed to it.

certainly there have been plenty of opportunities on the

RPi forum and twitter for someone to say yes we have a

design error and it is causing chip temperatures to get hotter

than they are supposed to.

On the recent "case with fan" thread:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=14323

bredman replies:

"1. The chips in the RPi are supposed to run hot, they are designed to operate safely to 120 degrees C."

On twitter, a similar question about fans is asked:

https://twitter.com/scottfrye/status/234232917583343616

Liz's reponse is:

"we're making good progress on the heat issue that some of

you are experiencing, with expert help from the other forum."

Oh wait, that's not quite what she said.  Instead she said:

"Why do you need a fan?"

Ron K Jeffries further clarifies: "It runs very cool, even when

overclocked to 900MHz.  Unless you live in the Mojave desert,

you'll not need a fan."

I think you said it best some months ago, that facts and honesty "interfere with her right to a new kitchen".

coder27 wrote:

 

There's a report today of a guy who thinks there is a correlation

between hot chips and ethernet cutting out and keyboard repeats.

 

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=14478

 

"Mine gets pretty hot. Heat I don't mind, but when it does get hot,

the ethernet cuts out and the keyboard repeats happen more often."

Here's my latest hypothesis.  We're seeing three outcomes of the regulatory battle between RG1 (1.8V regulator) and IC3 (LAN9512).

1.  RG1 has substantially higher Vreg than IC3 and thus provides essentially all the current for 1V8.  IC3's regulator switches off and IC3 runs nice and cool.

2.  IC3 has substantially higher Vreg than RG1 and thus provides essentially all the current for 1V8.  IC3 get very hot, but still functions OK, at least for now.

3.  RG1 and IC3 have almost identical Vreg and the regulation is unstable, with the current alternately being sourced by RG1, IC3, or both, depending on RG1 and IC3 temperatures.

(3) is probably quite uncommon since it requires almost idential Vregs, but if it does occur might add enough ripple to 1V8 to cause USB and Ethernet failures.  It would be interesting to put a 'scope on 1V8 near IC3 to see what it looks like on boards with USB/Ethernet problems not otherwise explained.  It shouldn't affect IC3's PLL since the PLL has its own regulator and its own 1.8V filtering, but if IC3 is rapidly warming and cooling you might get some PLL instability.

It's also possible that (2) is causing local heating inside IC3 that's slowing a critical path enough to cause USB/Enet failure.  If path delay is right at the edge, process variation or case design could make the difference.

Good summary.  It's worth pointing out also that voltage is only one electrical parameter here.  If any instability is present, the added inductance from the incorrect connection could also be relevant given that the LAN9512 expects nothing but decoupling caps on these tracks.

The 1V8 LDO powers PLL circuitry in the LAN9512, so stability is important.  Those 3 caps won't be decoupling the LAN9512 as effectively if they're simultaneously part of a larger on-board 1.8V mesh, even if that mesh is not misbehaving electronically.

Morgaine Dinova wrote:

 

Good summary.  It's worth pointing out also that voltage is only one electrical parameter here.  If any instability is present, the added inductance from the incorrect connection could also be relevant given that the LAN9512 expects nothing but decoupling caps on these tracks.  The 1V8 LDO powers PLL circuitry in the LAN9512, so stability is important.

According to the LAN9512 data sheet (Figure 2.2 -- Power Connections), the PLL has its own +3.3V to +1.8V regulator.  It appears to be wired up correctly in the RasPi schematics.

I wasn't so sure about their complete independence inside the LAN9512 when looking at the datasheet.

The VDD18ETHPLL and VDD18USBPLL lines are also connected to L3 which is specc'd at 100MHz so it seems strongly related to dynamic PLL operation (L3 is isolating ETH and USB sections from each other for RF, similar to L4 on the 3V3 side), and neither of those PLL lines has a tank cap like the 4.7uF on the 1V8CORE lines, so it doesn't seem to be caring about low-frequency stability.  That suggested to me that the PLL's 1.8V may actually be affected by the core 1V8 LDO, if not directly as a source (which seems unlikely since it's fed from 3V3) then at least indirectly through core logic.

When SMSC go to all the trouble of inductively isolating the USB and ETH sections of both their 3V3 and 1V8 LDOs, it's easy to imagine that they're not too impressed when their 1V8CORE pins are coupled to something foreign.

There are also some additional bits of information to consider based on reports of problems with Ethernet and the X1 crystal. If there are indeed power issues on the SMSC core that may produce unstable operation of the internal clock signals and ethernet is particularly picky about clock jitter and shape which may get the part to operate out of the IEEE specs. I've seen this problem with some Ethernet controllers/PHYs where temperature produces too much drift on the crystal/oscillator and the ethernet link is lost.

And who said that the parts on the R-pi are rated to operate at 120C ?

The PoP RAM chip on top of the SoC is rated for Commercial temp ranges, it varies from mobile to normal applications but it does not exceed 95C.

There is a lot of clueless folks at the R-Pi forum contributing wrong information to the already existing confusion.

-J