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Blobless Linux on Raspberry Pi

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Re: Blobless Linux on Raspberry Pi

#101
post #46

Earlier quoted context omitted.

It's really doubtful that more than a tiny fraction of RPi sales have gone to kids. Be honest here, whatever the RPi Foundation's marketing, the overwhelming majority have gone to hobbyists. The RPi is uniquely unsuited to an educational environment anyway. The SD cards are unreliable, especially in combination with the RPi's poor power filtering and the cheapo phone adapters it's usually paired with. Anyone who has…

SD card failures I'd love someone knowledgeable to explain why this happens. According to general opinion on the RPi forums, it's because SD card manufacturers cheap out all the time. I'd have something like a dozen SD cards running things like cameras over the years, and probably a hundred booting ESXi servers. And I've never seen a failure. Across three RPis, I've bought about seven SD cards, and from everything RP…

The ESXi servers by default regard your SD card as read only media, so normally they should not fail easily.

Re: Blobless Linux on Raspberry Pi

#102
post #35

Earlier quoted context omitted.

You are fighting the good fight, freeing one of the most common single board computers! That being said, besides quantity, why focus on the Raspberry Pi instead of Allwinner H3 based boards or another board where most of the support (including uboot) is already upstreamed & can be run with a fully libre stack?

If a "development" board does not let me run my own code in EL3 (Secure monitor mode), I'm not buying it, as simple as that. A lot of boards that use Allwinner chips will use a signed bootloader that exits secure mode before passing control to your code. My favourite is probably NVIDIA Jetson TX1 where development boards do not have a key fused in them and have documented TrustZone peripherals, so you're free to run…

Uhh, the H3 has supports TrustZone and has an efuse that is unset but can be burned with a signature, so its supportable in that regard.

Re: Blobless Linux on Raspberry Pi

#103
post #39

Earlier quoted context omitted.

Counterpoint: The pi runs Linux inefficiently, draws too much power and gets too hot. All of these could probably have been fixed with minimal support from broadcom (and a bit more open thinking from them during the design). Open source is not a crazy idea by a bunch of fanatics, it had real world implications.

>All of these could probably have been fixed with minimal support from broadcom (and a bit more open thinking from them during the design). Support from Broadcom is unlikely to fix it, the BCM283x family of SoCs are just a huge mess and in my opinion are either suited for really specific applications (TV boxes) or as "toys". The ARM core itself is integrated very poorly almost as an afterthought, since it wasn't in t…

Yes, 2837 is a 1995 soc design with a 64-bit quadcore forced into it. Their multicore support was probably thrown together in an afternoon by a junior asic designer on a hangover.

But some of the issues could have been worked around with better documentation.

Re: Blobless Linux on Raspberry Pi

#104
post #65

Earlier quoted context omitted.

>it uses the adapter to charge the battery and/or feed the regulator circuit, the key being there is a regulator circuit here. The Pi does not have one. Wait, what? Of course the RPi has voltage regulators. Do you think the Broadcom chip runs at 5V? There's a LP2980-N and NCP1117 shown in the schematic.

Yeah, and microSD cards run at 3V3. The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3. Oh, and people usually buy the 2-5$ range of power adaptors from Amazon, I'm amazed that no one has managed to burn down their house with this stuff.

>Yeah, and microSD cards run at 3V3.

Err, yes. Hence the LDO regulators.

>The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3.

The RPi has filtering capacitors. In general filtering capacitors are regular cheap X5R or X7R caps. They don't need to be anything special. Look at any LDO regulator datasheet.

> Oh, and people usually buy the 2-5$ range of power adaptors from Amazon

What does that have to do with the designers of the RPi? They don't have any control over which power supplies people buy.

Re: Blobless Linux on Raspberry Pi

#105
post #104

Earlier quoted context omitted.

Yeah, and microSD cards run at 3V3. The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3. Oh, and people usually buy the 2-5$ range of power adaptors from Amazon, I'm amazed that no one has managed to burn down their house with this stuff.

>Yeah, and microSD cards run at 3V3. Err, yes. Hence the LDO regulators. >The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3. The RPi has filtering capacitors. In general filtering capacitors are regular cheap X5R or X7R caps. They don't need to be anything special. Look at any LDO regulator datasheet. > Oh,…

> The RPi has filtering capacitors

It's hard to specifically assign blame to noise since it's such a personal and transient problem, but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering and if anything is doing things that are much more sensitive to noise due to its OS.

http://www.crazy-audio.com/2013/09/raspberry-pi-power-supply...

> What does that have to do with the designers of the RPi? They don't have any control over which power supplies people buy.

You shouldn't have to buy a power supply at all. The norm is that when you buy a piece of hardware it comes with an appropriate power supply. When I buy a $15 gigabit-ethernet switch from D-Link, it comes with a power adapter.

Again, the Pi Foundation wanted to hit their price target so they could put "A computer for $35!!!" in their advertising, so they cheaped out on something that probably costs $2 when you are buying a million of them. At quantity 500, you are already down to $4 when sourcing them from Mouser.

They also pretty much openly encouraged you to use whatever crappy USB charger you had lying around. The reality is most knockoff chargers are total crap, their current ratings are dramatically overinflated, and they certainly won't be delivering clean power anywhere near their current ratings, which again amplifies the problems with the Pi's lack of filtering.

All of this has been well-known for ages. Check out Ken Shirriff's excellent series of teardowns on cheapo USB chargers and his comparison to a genuine Apple charger. This was not news even at the time.

http://www.righto.com/2012/03/inside-cheap-phone-charger-and...

http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-ap...

http://www.righto.com/2012/05/apple-iphone-charger-teardown-...

Re: Blobless Linux on Raspberry Pi

#106
post #105
post #104

Earlier quoted context omitted.

>Yeah, and microSD cards run at 3V3. Err, yes. Hence the LDO regulators. >The problem is that a phone usually has better filtering capacitors, which the Pi lacks and thus any noise from the power line directly goes from 5V down to 3V3. The RPi has filtering capacitors. In general filtering capacitors are regular cheap X5R or X7R caps. They don't need to be anything special. Look at any LDO regulator datasheet. > Oh,…

> The RPi has filtering capacitors It's hard to specifically assign blame to noise since it's such a personal and transient problem, but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering and if anyt…

>but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering

What is your source for all these statements? How do the voltage regulation circuits in phones differ? If anything the phones ought to have more noise, since they're using switching regulators rather than linear regulators.

>Again, the Pi Foundation wanted to hit their price target

Yes, you got it. There's 1001 improvements that could be made to the RPi. If you made all of those improvements, it would not be affordable.

>They also pretty much openly encouraged you to use whatever crappy USB charger you had lying around.

They say to use a charger that's rated for at least 2.5A. That does not include most crappy phone chargers. They also sell an official RPi power supply which anyone is free to buy if they're concerned about this issue.

Re: Blobless Linux on Raspberry Pi

#107

Earlier quoted context omitted.

Yes but still, at that time these SoC alone were above the rpi board price point. If you wanted to sell something aronud 30 you had to do vendor tricks with odd parts.

Yes. Embedded engineers do this every day. BTW the Broadcom part is heavily subsidized.

Subsidized by whom? Who is losing money on the RPi?

Re: Blobless Linux on Raspberry Pi

#108
post #28

Earlier quoted context omitted.

The Orange Pi PC is $15, roughly comparable to the Pi 3 performance wise, and doesn't require any of this hilarity to boot with open source code.

See my other comment about Allwinner, but basically my biggest issue is that they lock down their bootloader with signing and do not allow you to execute code in EL3/Secure mode without exploits.

This is very sad because those H3/H2 based boards are SO much more interesting than the RPis. I can't but wonder why Allwinner is so hostile to OSS.

Re: Blobless Linux on Raspberry Pi

#109
post #106
post #105

Earlier quoted context omitted.

> The RPi has filtering capacitors It's hard to specifically assign blame to noise since it's such a personal and transient problem, but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering and if anyt…

>but as a general statement power quality is one of the biggest problems with the Raspberry Pi and I strongly suspect that the Pi is not really equipped to tolerate 270mv swings as are seen on cheap USB adapters. Phones deal with this quite fine, but the Pi has less filtering What is your source for all these statements? How do the voltage regulation circuits in phones differ? If anything the phones ought to have mor…

> What is your source for all these statements? How do the voltage regulation circuits in phones differ? If anything the phones ought to have more noise, since they're using switching regulators rather than linear regulators.

It's pretty self-evident that the circuits are different. The phone normally operates from its battery, the amount of ripple present from a battery is zero. I'm not sure what source exactly you want me to provide to cite the fact that a phone has a battery, anyone knows that.

Also, typically a phone will use a buck converter (or perhaps buck-boost) to drop its voltage, rather than a switching regulator.

Some phones do have problems operating while plugged into crappy adapters (the power does pass through), the most common being that the touchscreens stop working.

> Yes, you got it. There's 1001 improvements that could be made to the RPi. If you made all of those improvements, it would not be affordable.

And yet any network switch you buy off the shelf for $15 comes with a workable power supply.

But yes, that is my point, the parent was asking for reasons why you wouldn't buy a Raspberry Pi, and the fact that it's got a shitty power system that tends to result in SD card corrupt is a major reason you should not purchase a Pi and prefer a properly engineered product. I think we're in agreement.

The Pi Foundation themselves cite the cost of the switching-mode power supplies on their alpha boards as adding $2 to the bill-of-materials cost, leading to their decision to remove them from production boards. Terrible anti-consumer move, how much have you spent on burned-out SD cards so that they could hit their $35 price point?

https://www.raspberrypi.org/blog/power-supply-confirmed-as-5...

Anyway, any random piece of electronics comes with a power supply. A $15 network switch comes with a power supply, or a drive enclosure (those are even quite beefy ones!). Competing products like the ECS Liva come with their own power supplies too, and the total cost of the system is the same as the Pi.

> They say to use a charger that's rated for at least 2.5A. That does not include most crappy phone chargers.

They've backpedaled on this since the launch after problems started appearing. The official spec at launch was that the Pi pulled 700ma for Model B and 300ma for Model A, and pretty much any random charger meets that spec. Anyway, most chargers are significantly overstating the amount of clean power they can provide, because they expect the phone to be using them for charging, not for operating.

You can see the original statement from the Pi Foundation here: https://www.raspberrypi.org/blog/power-supply-confirmed-as-5...

And then after launch they started realizing they had problems: https://www.raspberrypi.org/forums/viewtopic.php?f=2&t=5420

> I'll be testing PSUs soon as well, although maybe not as thoroughly. It certainly seems that the Foundation may have been wrong in assuming that USB chargers produce the current they say they do and that all USB cables are reasonably constructed.

The fact that $1.99 adapters you get off eBay were built like shit wasn't a shocker to anyone, even at the time. That's a hilariously naieve assumption for them to make.

> They also sell an official RPi power supply which anyone is free to buy if they're concerned about this issue.

This only launched within the last year. Good on them for finally doing it, but it should be included with the device, and should have been included from day 1.

http://www.electronicspecifier.com/power/stontronics-manufac...

Re: Blobless Linux on Raspberry Pi

#110
post #19

I confess. I'm completely ignorant about the Raspberry Pi even though I have a 3rd generation I bought recently. So I don't really understand what the significance of "Blobless Linux" is. Is the Raspberry Pi an open-source software and hardware platform? If not, what is? What should I have bought if not the Pi3?

If your use case is for a low power server, something that many people seem to do, then a Raspberry Pi is suboptimal.

Something based on the Allwinner A20 makes a good choice as the SoC has an integrated ethernet (10/100) and SATA controllers, which means no USB-to-ethernet or USB-to-SATA half-arsery.

I am running an old A10-based Mele A2000 with wired ethernet and a 1 TB SATA HDD as a home server. Stock Debian with a mainline kernel and mainline u-boot 'just works' if you want to run a headless server.

If you want some GPIOs and other pins broken out, look at boards from Olimex [1] or Itead [2] or Cubie [3].

[1] https://www.olimex.com/Products/OLinuXino/A20/open-source-ha... [2] https://www.itead.cc/development-platform/arm.html [3] http://cubieboard.org/model/

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