RG1 1.8v regulator

Seems like a good suggestion - as you say at least we can compare results with some confidence, I think the issue on resolution, spot size is also a complicating factor.  From what I understand you will get the average of the spot size so any real hot spots will be averaged away.

I've been trying to find a IR lens that will give 10mm x 15mm as the total field of view.  Interestingly it gets even more complicated when you look at effective touch temperature and we need a gizmo called a "thermesthesiometer probe" but these are not commercially available as far as I have found - if you find one let me know.

NASA (slightly old but the most recent I could find) have suggested that 45C is tolerable (indefinitely) for polished metal with an effective infinite heat capacity, and obviously a very high thermal conductivity, but this does not play well to our circumstances unless we measure less than that.

So I think there are three issue in this thread:

1) Touch temperature concern.

2) Die temperature and effect on performance.

3) Effect on functionality of USB? (Circumstances yet to be determined)**.

I have not seen any reports that making the suggested mod fixes anything, I'm sure you will let me know if I've missed it.

As always - comments welcome.

Cheers

Pete

In my company we are moving away from buying some cheap components produced in China, it is well known in the electronics community that counterfeiting of components have been increasing substantially, like one of the more known cases being the Nichicon aluminium electrolytic blowing up on monitors and computer switching power supplies since the counterfeit part used a very low quality dialectic and the part does not meet the specs.

I must have replaced thousands of those in PC's, but that particular problem seems to be solved - at least from what I see.

From the people I know who work for chinese manufacturers it certainly appears that a large part of going to china is to do with getting counterfeit parts - if not the whole device!

Part of the problem is quickly going to become - if it hasn't already - that your 'original' NXP LDO will have been made in the same factory, on the same equipment, and to the same design as the chinese one. Maybe both will use the NXP design, maybe the chinese one. As long as they're not totally flaky and outlast the warranty there's a part of me that thinks nobody will care - stuff dying sooner means you replace it sooner and someone makes another sale. The beancounters like that idea

Have we all seen this before ?

I have no idea if it's real or someone just did a mockup to illustrate a point, but certainly made me smile

jamodio wrote:

 

What really concerns me (after all I'AM a "concern troll") is that this type of situation serves as a learning experience so we don't repeat the same errors or wrong processes, but I doubt that if there is ever a new revision or version of this board, we'll have the opportunity to review it before the hype-pi 2.0 starts.

+1.

Feedback on issues is part of the engineering process.  That's alien to Liz's hype & fandom process.

PeteL wrote:

 

As always - comments welcome.

+1

I've been trying to quantify one particular area of faulty operation, RF mice on self-powered USB hubs .  With dozens of tested (device X hub) combinations, and all 8 of the data points for RF mice showing complete failure on Pi, it's a very black-and-white test bench for USB functionality.  I happen to have a hot-running LAN9512, so I may be able to provide relevant testing if the 1.8v issues are thought to couple to USB operation.

Morgaine.

J

Connecting the two 1V8’s is a sub optimal piece of design (you can look that up in the engineering translation dictionary - starts with a 'c' ends in ‘up’), and I didn't think that was of debate.

The design did go through extensive review within the 'inner circle' of supporters who 'know' and have worked with the chips before especially the BCM. Both prototypes and pre-prototypes had this same connection and that of course made it more difficult. I also suspect, had there not been some reason to go and look, it would have never been identified. Just for the record, your technical input is appreciated, but rather than just implying - you could have just asked? Maybe you did earlier and I missed it.

We tried to do the best job possible with the limited support and resources that the early phase project had. (We were going to make 5000-10,000 beta boards max). None of the early stress testing revealed the issue and only a small population (sub 0.01%) are reported to run unbearably hot (although more may, just not flagged up because it does not concern their owner - they are just having fun with it). Of the returns I have for analysis, I have still have not found a real ‘steamer’. These could be in part due to poor underfill or even a short/defect elsewhere on top of what we are asking the chip to do.

There is an implication in posts that this is responsible for something else to do with USB but to date no info is forthcoming? (Stop press - just seen that other thread - will go and look later).

It doesn't matter if you spend £1 or $10M things slip through, and there have been some very high profile events in that $10M category in all walks of engineering!

I remember saying at the outset that Pi would never be perfect - just doesn't happen in engineering there is always something to be optimised, improved. What we do need to do is measure, evaluate, garner input and decide what, if anything, needs to be done. And I do appreciate the work done by people on this thread already.

Pete

Question is - were the Rubycon's real !

P

Pete,

You wrote:

"There is an implication in posts that this is responsible for something else to do with USB but to date no info is forthcoming? (Stop press - just seen that other thread - will go and look later)."

I'm quite sure that there is no established connection at this point

between this 1.8v power issue and any USB or other functional problems.

Users with hot lan chips have been having USB problems, but so have

users with cooler lan chips, so the USB problems could very well be due to

other causes.

SMSC has said "don't do that", but they haven't said what will happen

if you do.  We've seen pretty convincing evidence that the lan chip

will get hot, but don't know if it will malfunction, or cause a malfunction

on the other devices connected to 1.8v, or whether its expected lifetime

will be shortened.

you wrote:

"only a small population (sub 0.01%) are reported to run unbearably hot (although more may, just not flagged up because it does not concern their owner - they are just having fun with it). "

I'm not sure what you are basing your statistics on.  Is it the return rate?

I suspect that the rate is higher than 0.01%.  If the rate was that low,

then certainly there would be no hesitation to announce that due to a

design defect, a very small number of boards have chips that run blisteringly

hot, and any user who is unlucky enough to have gotten one is welcome

to exchange it.

you wrote:

"We tried to do the best job possible with the limited support and resources that the early phase project had."

I don't think anyone would deny that you did a fantastic job with the limited

resources you had.  But I think jamodio's point is that releasing schematics

prior to production would not have cost anything, and could have resulted

in great savings by uncovering such errors before mass production.

I am not a hardware guy, but I am quite surprised to see that hardware

schematics aren't clear about the direction of power flow.  It is a bit

ironic that the beta board had a string of decoupling capacitors that

should have been connected to 1.8v, but wasn't, and the production

board has a similar string of decoupling capacitors that shouldn't have

been connected to 1.8v, but was.  But there is nothing in the schematics

to show which pins on the ICs have power going in, and which have

power coming out.  So it is very difficult to check the schematics to

find these kinds of errors, where components are either not connected

to any source of power, or are connected to more than one source.

At this point we are completely in the dark about what hardware revisions

are contemplated, other than Eben's mention of some unspecified pcb

change for FCC/CE residential compliance.  Hopefully that will change.

Eben said he wanted to fix the FCC/CE issue prior to the educational

release.  Since the 2012/2013 school year is about to start, the timing

seems really odd not to have fixed that by now.  The timing also seems

really odd not to have published the user's manual by now.  Amazon is

showing a projected date of 16 October.  So are you aiming for the

2013/2014 school year?  If so, I'm quite sure you will need 512MB ram

to be competitive.

First of all thanks for being here and for following up. I really appreciate the work you have done and I truly believe that some of the mishaps from the RPF are not your own making.

 

Connecting the two 1V8’s is a sub optimal piece of design (you can look that up in the engineering translation dictionary - starts with a 'c' ends in ‘up’), and I didn't think that was of debate.

Well, you may call it "sub optimal design" but it is actually an error, and in my dictionary it starts with 'f' and ends in 'up' ;-)

 

The design did go through extensive review within the 'inner circle' of supporters who 'know' and have worked with the chips before especially the BCM. Both prototypes and pre-prototypes had this same connection and that of course made it more difficult. I also suspect, had there not been some reason to go and look, it would have never been identified. Just for the record, your technical input is appreciated, but rather than just implying - you could have just asked? Maybe you did earlier and I missed it.

Obviously the process didn't work, and as you clearly know in the previous prototype it was reported that various power connections were missing, kind of a surprise since part of the 'inner circle' was apparently involved in the design of the BCM SoC chip. Perhaps the 'inner circle' has a very small radius and some of the supporters actually "don't know." Not just me but many other asked while before the boards went to production for schematics/gerbers and the only we obtained was a crop showing a psu section. I reported the problem as soon as the schematics were made public, and it didn't took too much know how, just reading the SMSC datasheet to figure what each pin was used for, something that we don't even have for the SoC part.

And about asking, I asked what else is on "the list", no response yet.

  We tried to do the best job possible with the limited support and resources that the early phase project had. (We were going to make 5000-10,000 beta boards max). None of the early stress testing revealed the issue and only a small population (sub 0.01%) are reported to run unbearably hot (although more may, just not flagged up because it does not concern their owner - they are just having fun with it). Of the returns I have for analysis, I have still have not found a real ‘steamer’. These could be in part due to poor underfill or even a short/defect elsewhere on top of what we are asking the chip to do.

The foundation should have put they arrogance away and ask for help and additional support, there has been a large group of people willing all the time to cooperate, and they are still out there but the RPF attitude has been always "what we did is perfect and we know everything." I'll not trust any number, percentages or analysis derived from them given that there are no public numbers about how many boards have been manufactured, how many have failed, how many have been sold. how many have been shipped, how many have been returned, etc, and there is no formal or reasonable system to track complains/failures/fixes.

There is an implication in posts that this is responsible for something else to do with USB but to date no info is forthcoming? (Stop press - just seen that other thread - will go and look later).

I'm not sure if there is a direct connection with several of the problems reported with USB. Certainly the entire power architecture does not help, but there are some hardware/firmware issues related to USB where things are not working as expected and somebody is now reading the Verilog files for that piece of silicon on the SoC discovering some limitations and other stuff hidden behind the obscurity of the drivers.

I know that everybody have tried to do their best, but recognition for a successful endeavour comes from producing positive results and not from the effort put to get them.

My .02

-J

So I guess it is not worth me publishing here what I know and what I can measure?

I do take issue with your final comment - it has been a success so far - with some measure of "success failure" thrown in.

I've been talking to users who just have one or two and are over the moon with them (faults issues and all) and they tell me that they have already learnt so much.

My overall positive view may yet be proved wrong, but as I said right at the outset it isn’t perfect, never will be - we just have to remember why we are clearing the swamp!

Off to watch the Olympics on TV

Pete

I am not a hardware guy, but I am quite surprised to see that hardware

schematics aren't clear about the direction of power flow.

In many years of working in the subcontract hardware assembly business I've seen hundreds of schematics from all sorts of companies, from the biggest names to tiny one man outfits and I've rarely seen anything indicating power direction.

This sort of thing wouldn't have been a problem in years gone by as it was rare for IC's to have internal regulators and often power was supplied from an off board supply so it was obvious.

Things change, technology gets more complex, leaving room for ambiguity and errors to creep in.

IME Petes schematics are pretty good, they lack some things you'd normally find on much larger schematics like a cross reference of refdes and signals to page and location, but for four pages most of that stuff isn't really necessary.

lol.. nope.. it's like one of those russian dolls you keep removing another layer until you get to the 0201 smt cap somewhere inside