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?
> Is the Raspberry Pi an open-source software and hardware platform?
No, the hardware isn't open, and not all of the software is, either. It requires a closed-source blob of code to boot the system. There's "real" firmware in the VC4 chip, which is the first part of the Pi to come up, some binary blob bootloader files, and drivers handling graphics and hardware decoding that are still closed. There is an open-source 3D driver, but it's missing some capabilities from the closed one (hardware accelerated video decoding), but includes some extras (some degree of support for non-mobile OpenGL).
The chips from most other vendors are at least bootable without blobs, even if video output won't be properly accelerated.
There is no sane reason which would explain why you should not have bought a Pi. Open or not it would not make any difference to more than a small room full of people. A bunch of people spent years designing hardware and negotiating with people to get the Pi built at a low cost and it's become the best selling UK computer ever with over 10,000,000 sales. It's succeeded at what it was supposed to do; provide an educational platform for kids.
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 the original design, the BCM283x family is just BCM27xx family VideoCore4 VPU+QPU combinations with an ARM core hacked (and I really do mean hacked) on top.
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.
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 used a RPi has had to deal with filesystem corruption and SD card failures, intermittent USB bus brownouts, etc, and I can only imagine the nightmare of having to maintain a lab with 50 of the things. You can't PXE boot them (let alone remote-manage them) because they have no BIOS, just a blob on a physical card that needs to be swapped out.
The Pi should have had eMMC day one, and shipped with a proper power adapter and better power filtering. But much like their choice of Broadcom SoCs - they made a political decision that they were going to market primarily around the $35 price point, and so they cheaped out on $5-10 worth of hardware and ended up with a device that was entirely unsuitable for their stated purpose.
And the terrible thing is - the PC is not the sole component in the system anyway. The Pi still needs a case, a a monitor, keyboard, switches, etc, and if you are trying to stand up a lab for the first time it's not like you have 50 monitors or keyboards laying around for free, you need to buy those. So you are looking at more like $150 per system anyway, and the $10 you save on cheaping out on the hardware becomes a meaningless fraction of the total cost. Just buy the right hardware the first time. An ECS Liva is only like $75 anyway, it comes with a case, onboard eMMC, AC adapter, and wifi, you've made up the difference in cost in accessories included in the box.
There were many other terrible design decisions as well - such as the choice of USB as a system bus, which is again entirely unsuitable, especially when you are running on a low-power processor where running the USB bus full-tilt eats a significant fraction of your CPU cycles. It's like that shitty Mac Performa x200 road-apple design with the split half-width left-hand/right-hand busses which couldn't talk to each other, it eats up all your cycles by just using your disk or network. Even if the processor on other boards is no faster in synthetic benchmarks - they have a proper system architecture with SATA and often USB 3.0 and gigabit ethernet that makes an enormous difference in real-world performance.
Furthermore - the Pi was plagued by driver problems with its USB stack for years. It would randomly drop USB frames when operated at USB 2.0 speeds, and it took upwards of 2 years after launch for the Pi foundation to get around to pushing a fix (again, because they chose a processor for which they could not release documentation, and they did not employ enough staff to actually fix their issues). How on earth are you supposed to do education on it when they can't even get their system bus to be stable?
You know what I would do if I was running an actual lab? ECS Liva Xs, or other cheapo x86 PCs running a standard stack. Or go down to your university surplus store and pick up as many generic Dell boxes as you need for $50 apiece, out the door, ready to work. The Pi is good for embedded hobbyist work (the i2c interface is very powerful), but it totally fails as a machine for teaching programming compared to Ye Olde White Box.
I tried to run a pair of RPis as my fileservers for about a year and a half, and I finally just gave up and sold them. They aren't good for the "mini Linux PC" application at all, compared to properly-designed hardware that you can buy for only a little bit more money (or sometimes even less money, especially when you work out the total system cost).
(note: Pi3s can finally PXE boot without a SD card, which is like the bare minimum requirement for running an educational PC lab without going insane)
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 RPi users tell me, that's a totally normal failure rate.
Edit: In regards to cheap whiteboxes, no such options allow access to GPIO ports. I've learn plenty of interesting things about soldering circuits by having these, without considering the Pi a PC learning tool.
In regards to cheap whiteboxes, no such options allow access to GPIO ports.
The parallel port on older PCs works reasonably well as GPIO; you can get expansion cards for those which don't have one (they seem to have gone up in price now but they used to be extremely cheap.) Since this is an actual external interface it will be more robust than the GPIOs directly connected to the SoC of the RPi, and if you use expansion cards you can just swap them out if they do get damaged.
> Across three RPis, I've bought about seven SD cards, and from everything RPi users tell me, that's a totally normal failure rate.
Sounds about right. I went through maybe 4-6 cards on 2 Raspberry Pis in a year and a half.
> 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
SD cards are basically uniquely ill-suited to be used in a Raspberry Pi.
First off, cheap SD cards have no wear levelling. The flash controllers are super primitive. They are designed to be written sequentially until full, and erased, like you would use a camera. A regular Linux operating system is not designed to moderate its writes, it will happily do all kinds of work and logging on /var and other places, doing tons of heavy random writes that put tons of wear on the card (write amplification/etc), and there is no levelling taking place. The flash cells just burn out.
Real mobile OSs are much smarter about what they write to flash, and they have eMMC that usually has at least a slightly smarter controller optimized for more random-ish loads, and/or is totally under the CPU's control with a filesystem designed to work with flash.
Next, flash doesn't like to be powered off during erases or writes. In some cases it can actually corrupt operations that were successfully completed. The flash cells do not get as much charge as they should and can decay prematurely.
Nor does flash like operating under questionable power conditions either. The flash can think it's successfully completed the operation, the processor will keep on trucking, but if the voltage drooped too much, the write doesn't persist. In some cases, this can cause the flash to get trapped in a "bricked" state that needs a hard reset to clear properly (which can't be done with a SD card).
The Pi also has no/very little power filtering. Your phone doesn't ever run off the charger. 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.
In short - the Pi is an absolute worst case in terms of power. Your average camera or phone has a battery, so the power is clean, full-on power faults are quite uncommon, and the device can monitor voltage and stop doing writes before things get critical. Not only is it really, really easy to accidentally or purposefully unplug the Pi, or flip the power strip off, but the shit-tier phone chargers that get used with it have terrible power filtering and tend to have wildly insufficient power delivery capacity. Under load, the voltage droops and the noise on the power line gets pretty intense.
With the first-gen Pis, there was an additional physical issue with the SD cards. The cards are just made of plastic, they are meant to go into a slot in a camera or phone that physically supports them, they are not intended to just hang off into space. The Pi does actually get fairly warm, especially if you have it in a case, and hot plastic warps. The card loses contact half-way through a write and there goes your file system.
Adding a "UPS" board that can command a soft-poweroff, a decent microSD card (Samsung EVO are reputedly the most reliable on a Pi), and a "low-profile" microSD adapter that doesn't hang off into space quite as much reportedly make a pretty big difference in reliability, as does using a purpose-built adapter from a reputable vendor like Adafruit or something. Not running it in a case probably helps too.
Again though, once you spend the money to fix the flaws, you could just buy something that just includes what you need to boot up right in the box.
I really can't emphasize enough how much all of this is actually the result of poor design. If the Pi Foundation would have chucked a 2 GB eMMC chip on there and added a barrel connector and a decent power supply, these issues would be essentially eliminated. And IMO the issues are pretty much show-stoppers for any chance of reliable operation.
> In regards to cheap whiteboxes, no such options allow access to GPIO ports. I've learn plenty of interesting things about soldering circuits by having these, without considering the Pi a PC learning tool.
That's definitely true, but you can also buy a Bus Pirate that will be capable of adapting most simple embedded units to any PC.
You really only need the Pi's GPIOs when you are doing something that involves really high throughput or really low latency. The examples I've heard are video streams and using a GPS board as a reference for an NTP server - they exist, but for your every day "talk SPI/I2C to a sensor" or "count freqency counts from a sensor" the Bus Pirate does very well.
>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.
>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.
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.
> 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.
>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.
> 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?
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.
> 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.
> 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.
I was asking for a cite on the claim that the phone has a better voltage regulation circuit. AFAIK both the RPi and phones are using jellybean switching regulator ICs to convert and regulate the voltage. Even an expensive switching regulator is going to have a hard time competing with the PI's linear regulators in terms of output noise. (The Pi, of course, can afford to waste a bit of power, whereas the phone needs to juice all of the battery capacity.)
>Also, typically a phone will use a buck converter (or perhaps buck-boost) to drop its voltage, rather than a switching regulator.
Erm, a buck converter is a kind of switching regulator (one that drops rather than increases the voltage). See for example the buck/boost/etc. options under 'Topology' in Mouser's switching regulator category, or the Wikipedia definition:
>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.
This undermines your point that phones somehow have better voltage regulation circuitry than the RPi. Many that will run directly off USB power have exactly the same issues.
>Good on them for finally doing it, but it should be included with the device, and should have been included from day 1.
But why are you still advising people not to buy the Pi because of power supply issues? I bought my first Pi a few months ago and made sure to get an adequate power supply (not difficult). I haven't had any problems.
>and so they cheaped out on $5-10 worth of hardware
The problem is that if you keep not cheaping out on $50-10 worth of hardware, you end up with something that costs $200. Everyone has their own pet peeve with the RPi which could be fixed for an extra $5.
> 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.
That's great, the hard work put in by hobbyists has made the Pi an even better platform to teach the kids. And their purchases have helped financially support the educational mission. I say this as a hobbyist who started out picking up a Pi and has now directly taught kids.
> The RPi is uniquely unsuited to an educational environment anyway.
A traditional educational environment, maybe, but it's exactly those environments that have made computing such a dry and uninteresting pursuit in the first place. The computer lab at my school and college was tragic. I can only imagine how much I'd have loved to hack on a Pi, and I'm glad to be a small part of the effort to make that opportunity available to present and future generations.
> The SD cards are unreliable
I've used Pi's non-stop since day 1, and it's been a large part of my career for over 3 years. I can count the number of SD card failures I've had on one hand. I've never been particularly careful about shutting them down. I have two running on my desk 24/7 for development/testing. We've have two running in our post room, hard powered on/off every single day for 2 years. I think reports of unreliability are greatly exaggerated.
> the cheapo phone adapters
There's an official Pi power-supply for that. I certainly wont argue that terrible phone adapters are a problem though. It was the answer to every problem report on IRC for years :D
> You can't PXE boot them
The Pi 3 can PXE boot and boot without SD cards from, albeit not all, hard disks and other USB-attached storage.
> The Pi should have had eMMC day one
I think the cost of this wouldn't have helped with traction.
> shipped with a proper power adapter
Yup! Albeit, cost again. And, arguably, there are pretty good reasons not to ship a microUSB power adaptor, since most of us already have a tangled mess of them anyway from a dozen past phones. It's just unfortunate the phone ones were/are awful.
> The Pi still needs a case
It doesn't need one, but they look pretty :D Incidentally it's because someone recognised the demand for a case that I have a job that I love. Oh and people love to accessorize, so the ability for a customer to choose one to their liking is often a positive part of the experience.
> a monitor
Most people had an HDMI TV, but in retrospect the inclusion of HDMI/RCA led to a whole aftermarket of HDMI->VGA adaptors since schools are stuck in 1998. I think it's important to reinforce that learning doesn't, and absolutely shouldn't, only happen in schools.
> a proper system architecture with SATA and often USB 3.0 and gigabit ethernet
To hobbyists, maybe, but then they'd have cost $100 and been another unsung bit-player like the BeagleBone Black (Disclaimer: I loved the BBB). The Pi's biggest success was shaking up market, perhaps even creating one, and gravitating a whole bunch of people to a common cause. They also proved there was a market, so now if you want those things, there are plenty of alternative choices! And then they did it again with the Pi Zero- blatantly giving the market an "we're not going to watch you hit $9, $8, $7, $6 price points just for headlines. Get to the point" shakeup. You don't have to buy a Zero, but you'd be on rocky ground if you tried to argue that your options aren't better because of it.
> Furthermore - the Pi was plagued by driver problems with its USB stack for years
Ugh. shudder memories! But largely irrelevant these days.
> it totally fails as a machine for teaching programming compared to Ye Olde White Box.
Having run several workshops using the Pi, and contributed to more, I disagree. If for nothing else other than it's different enough to not simply put people off from the get-go. "Learn programming on these boring old white boxes" is not nearly as exciting as "learn to interface the real world with minecraft on credit-card sized computer." The low cost and educational push has also enticed a wave of enthusiastic geeks out of the woodwork, eager to teach anyone who'll listen. I know and deeply respect many of them, and I've had tremendous opportunity to make a positive impact on people's lives that perhaps I wouldn't have ever realised without the Pi.
> I tried to run a pair of RPis as my fileservers for about a year and a half
Yup. They are totally awful for this purpose, or at least just barely adequate, but that doesn't reinforce that they're awful at everything else.
> running an educational PC lab
I think you perhaps have too narrow a definition of education. I think the Pi excels because it fascinates people outside of a sterile classroom environment. Nobody is going to build and battle a robot, or create a 20 square foot version of whack-a-mole, or make a power-glove controlled robot arm, or a "disco" button that explodes their living room into song and light... out of a bunch of computers PXE-booting and tethered to ethernet.
The effort put into Blobless linux is itself a fantastic example of people using the Pi to push their own boundaries and learn things. And you say it's failed at being educational? Nonsense.
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].
Is the Raspberry Pi an open-source software and hardware platform? If not, what is? What should I have bought if not the Pi3?