22 ms·
A Xenon flash will cause the Raspberry Pi 2 to freeze
- mholt 12y agoShortcut to a video of this phenomenon: http://youtu.be/wyptwlzRqaI?t=1m29s http://youtu.be/wyptwlzRqaI?t=1m29s
- alephan 12y agohttps://www.youtube.com/watch?v=4huRNCrwfNw https://www.youtube.com/watch?v=4huRNCrwfNw
- mholt 12y agoIs your cursor nyan cat?
- jstalin 12y agoHow do you do that? I want a nyan cat cursor!
- bluehex 12y agoIt appears to be Nyanology[1] on Terminology[2] [1] https://github.com/anisse/nyanology https://github.com/anisse/nyanology [2] https://www.enlightenment.org/p.php?p=about/terminology&l=en https://www.enlightenment.org/p.php?p=about/terminology&l=en
- dietrichepp 12y agoReminds me of old EPROMs. You can buy special "light sensitive" transistors, but they're really just ordinary transistors with a window in the case, since ordinary transistors are light-sensitive. You can even use an ordinary 1N4148 diode as a solar cell, it just doesn't generate much power. The fix is simple: apparently, you just have to cover U16, which controls the power supply.
- adestefan 12y agoLEDs can also be used for narrow band detection. It's called the Mims effect since Forrest Mims was the first to publish about it.
- pmalynin 12y agoExplanation: Camera's have capacitors that charge up in order for the flash to happen. They are usually quite powerful. Now during the discharge (aka flash) what you have is very high energy electrons flowing across the wire creating aa magnetic field, coupled with the electric field of the electron you get a mild EMP. And if it is light sensitivity then it should be tested with a bright continuous light
- rblatz 12y agoWhich is completely incorrect. There is a light sensitive chip on the board. They state which chip it is in the link.
- thrownaway2424 12y agoThe entire purpose of a camera flash is to create a directed electromagnetic pulse.
- djmanning 12y agoThe entire purpose? Not really. I think it has something to do with a mess of directed photons.
- thrownaway2424 12y agoDo you discern some difference between "light" and "electromagnetic radiation"? Because the former is a subclass of the latter.
- falcolas 12y agoFor a "that's the joke" - light is on the EM spectrum, so a flash directing light will direct an EM pulse. :)
- baxter001 12y agoI am SO going to start referring to flash-lights as directed electromagnetic pulse generators, albeit ones with higher than normal pulse durations.
- nacs 12y agoThis was clearly designed to sell more opaque cases. /s Or to look on the upside, the Pi now comes with a free photodetector.
- ozy23378 12y agoThat Pi isnt very photogenic.
- thought_alarm 12y agoWhy would a switched-mode-power-supply chip be photosensitive?
- pjc50 12y agoAll silicon is photosensitive to some extent. The power supply will be one of the few chips which is primarily "analog"; in particular it will have a bandgap voltage reference. That's exactly the sort of thing to be badly affected by a charge pulse from the flash. Glitching the power supply will then destabilise the digital logic it's powering. The real question is how the light manages to get through the epoxy casing.
- jarvist 12y agoEpoxy resins are pretty transparent by themselves, opaque ones have additional materials or dyes added. Most dyes (also aromatic organics) are not active (i.e. transparent) in the near-IR.
- swamp40 12y agoYes, but if you were tasked with designing the epoxy that was going to be used in every IC everywhere, I would hope that you would go through the extra effort of adding dyes that were specifically opaque to UV and IR.
- rasz_pl 12y agothere is no epoxy, smps controller is a flip chip bare die bga
- swimfar 12y agoNot exactly the same thing, but here's a really cool hack where it's possible to use a photosensitive dram chip as a digital camera. https://www.cs.uaf.edu/2007/fall/cs441/support/dram_sensor_1984_whitehead.pdf https://www.cs.uaf.edu/2007/fall/cs441/support/dram_sensor_1...
- thrownaway2424 12y ago
- deleted 12y ago[deleted]
- nh 12y agoGood find OP! I wonder how many electronic devices would have similar problems if we took out the covers?
- thrownaway2424 12y agoAll of the badly-designed ones and none of the well-designed ones :) Often you'll see audio equipment with LED-biased voltage amps where the LEDs have some opaque glop slathered on them so they don't make popping sounds under bright lights, and to a lesser extent so multiple channels inside the same box are optically coupled, which is a concern. LEDs are photovoltaic like any other semiconductor but for obvious reasons they are not sold in opaque packages. You could probably find devices that are disturbed by loud sounds and physical shock, because ceramic capacitors are microphonic.
- thrownaway2424 12y agoThat comments thread contains a head-smacking quantity of ignorance. "Is it the light or the EM pulse?" What?
- eternauta3k 12y agoHe's asking if it's RF interference or just the light.
- lotsofmangos 12y agoRF interference is long wavelength light and the successful filter was blue-tack, so probably not.
- eternauta3k 12y agoRF is not light and that's a pointless remark. But right on your second point.
- lotsofmangos 12y agoRF stands for radio frequency, and defines a band of electromagnetic radiation, popularly known as light, that is on a continuum of frequencies that above RF pass through visible light and on towards gamma rays. In simple terms, whenever something possessing charge moves it generates an electromagnetic wave associated with the motion and at right angles to it. Visible light is generated by motions of electrons at an atomic scale, radio frequency is motion of electrons at the scale of antennas, but they both generate electromagnetic waves quantized as photons. edit - darkmighty. Electromagnetic radiation at radio frequencies is popularly known as light in contexts such as speed, but not in contexts such as colour.
- darkmighty 12y agoRF refers to specific frequencies of radiation, which are not popularly known as light at all. Radio is usually in the MHz range to a few GHz (10^6-10^9 Hz). Light starts a hundreds of Terahertz (10^14 Hz). The behavior is qualitatively different at usual scales due to quantum mechanical behavior (light is difficult to emit/absorb coherently -- it's more particle-like) at high frequencies. A photon striking a semiconductor will probably displace an electron if given an adequate bandgap, creating a voltage spike (which is nonlinear -- i.e. the problem isn't a propagating terahertz wave obviously). An incident radio wave will cause voltage spikes through coherent induction in the wires (i.e. they act as an usual antenna).
- swamp40 12y agoA xenon tube is a spark gap. If there's anything in this world noisier than a spark gap, I don't know what it is. I think the first radio transmitters were spark gaps. The energy flies thru the air, and is coupled onto the power line. The power supply doesn't cope well with the oscillations, and hiccups. I see the notes about U16 being photosensitive, but if it is a black epoxy like most IC's, I'm not buying that light gets into it. It's possible that blue tack shields the EMP a bit.
- lotsofmangos 12y agoA light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of one in or close to the visible spectrum, otherwise blue-tack would be useless. edit : The word light is commonly used as shorthand for variously the whole EM band, the near visible EM band and just the visible EM band. If you are talking about the speed of light, it includes radio and gamma. Discussing the colour of light on the other hand and you are referencing the visual system. As soon as you start talking about visible light however, you are widening the definition of light again to include IR and UV and more, otherwise you would not need to clarify with the word visible. edit 2 - darkmighty. I am not talking about the xenon bulb producing an RF EMP from the lamp flashing circuit, I am merely continuing the terminology used elsewhere in this thread, that a flash of visible light is also quite clearly a form of electromagnetic pulse. edit 3 - foobarbecue. Radio as it gets shorter becomes microwave, then IR, then red, through green, past blue, goes to UV, then xrays, then gamma.
- krenoten 12y agoTo the downvoters of the above comment: if it's technically incorrect, say so. I don't know if it is or not, but it's certainly not an offensively worded comment. When you downvote rather than respond, you are actually spreading ignorance. A downvote is an effort to mute. A half-muted incorrect technical comment will encourage far more ignorance than a properly corrected, visible one. Don't encourage ignorance.
- ChuckMcM 12y agoThat is fun, reminds me of the 'yelling at the drives slows them down' video.[1] [1] https://www.youtube.com/watch?v=tDacjrSCeq4 https://www.youtube.com/watch?v=tDacjrSCeq4
- tdicola 12y agoOh neat, I just reproed it with a Pi 2 and a Canon Speedlight flash. I'll put my scope on the power lines and see what's happening when you flash the board. Sounds like from the thread one of the power ICs is photo sensitive. edit: Wow yeah, here's a look at the 3.3V power line when you flash the board, it drops almost down to 0V and then wildly fluctuates for about 100 nanoseconds: http://imgur.com/hG86pRy http://imgur.com/hG86pRy edit 2: Another interesting measurement, with the board _totally unplugged_ and flashing it you can see a big voltage spike on the 3.3V rail. Up to 6-7 volts or so for a few nanoseconds: http://imgur.com/td262QK http://imgur.com/td262QK I guess not only can you learn about electronics but also Einstein's photoelectric effect with the Pi 2!
- noonespecial 12y agoAre you sure that's not induced current from the power spike required to operate the flash or the spark-gap inside the xenon tube? You've got the gear set up... would you mind terribly repeating the experiment but blocking the light with cardboard or something?
- robkix 12y agoIf I understand correctly the Speedlite is battery powered, so as such shouldn't cause any voltage spike on mains.
- nitrogen 12y agoIt's not a mains spike, but an EM discharge caused by the rapid voltage and current changes in the flash, that the parent comment is considering (IIUC).
- noonespecial 12y agoYes thankyou. This is what I'm getting at. The momentary power flow in a xenon flash is very large. A great big capacitor charges up and then discharges very rapidly to create the bright flash of light. There is also a high voltage exciter coil that fires to kick the xenon tube into conduction at the beginning of the flash cycle. Both of these could be very disruptive to nearby digital electronics. I thought the original poster would be in a very good spot to help us determine if the effect if photoelectric or the result of EM because he's got everything set up. All he has to do is repeat the experiment while blocking the light from hitting the Pi.
- Alupis 12y agoI just ordered two of these, and they will arrive on Tuesday. Makes me sad because I'm imagining a Raspberry Pi 2.1 release in the near future now...
- jonah 12y agoThe update will be a piece of black tape or epoxy over that component.
- zapt02 12y agoi'm seeing a market for chip "protectors" coming up, like the heatsinks that started selling for the original Pi
- lovelearning 12y agoBugs like these are the reason I never order version 1 of anything new.
- yuhong 12y agoAs a side note, the power supply chip directly uses the 5V from USB, right? Wonder if it is tolerant of 3.3V as common when running from batteries.
- psgbg 12y agoRelevant. Red vs Blue "EMP" https://www.youtube.com/watch?v=SMCsRkH-9AA https://www.youtube.com/watch?v=SMCsRkH-9AA
- tonteldoos 12y agoA computer with actual strobe-induced epilepsy. Looks like the singularity is closer than we thought.
- Johnythree 12y agoOne of the standard tests to gain an EMC Compliance Certificate is a spark discharge test. Any experienced engineer will have a Spark Generator (Car Ignition coil, spark gap and short Dipole) to test to see if his latest project misbehaves when confronted with Impulse Interference. As an EMC Investigator I would always carry a spark generator to demonstrate to newby engineers why EMC Compliance is so important. I've seen a spark from 50ft away crash or reset a microprocessor system. Just the static discharge from walking on carpet is often enough.
- hueving 12y agoThis is not the same thing. The cause is from the burst of light, not EM.
- TheSwordsman 12y agoWhat if I told you that light is EM?
- hueving 12y agoI would tell you that pretending there isn't an implied distinction for everyone involved in a modicum of applied science is as counterproductive as arguing about the editor chosen for a coding tutorial.
- arnie001 12y agoIt's interesting this was not caught before..
- sqren 12y agoVideo demonstrating the issue: https://www.youtube.com/watch?v=wyptwlzRqaI https://www.youtube.com/watch?v=wyptwlzRqaI
- Animats 12y agoThere's nothing mysterious about this. Semiconductor gates are light-sensitive. There's usually carbon black in the plastic of plastic-packaged ICs to prevent interference from light. The opacity isn't perfect, though. For that you need ceramic or metal-encased ICs. Still, this is a rare enough problem that IC data sheets don't specify a maximum tolerated illumination level. Try some laser pointers, especially towards the blue end of the spectrum where the photons have more energy. You may be able to trigger this effect by pointing at a specific IC.
- rasz_pl 12y agored laser makes it crash too
- Animats 12y agoOK, that part is a reject. It will probably crash in bright sunlight, too.
- poizan42 12y agoApparently the U16 IC is completely missing its casing
- rasz_pl 12y agoits not missing it, its just a specific packaging type (flip chip). Its supposed to be used in products with full enclosure, or under a heatsink. For example almost every single CPU and GPU nowadays uses some fcbga packaging (flip chip on ceramic/pcb carrier), but they are all hidden under heatsinks and often additional heat spreaders. http://www.maximintegrated.com/en/app-notes/index.mvp/id/4002 http://www.maximintegrated.com/en/app-notes/index.mvp/id/400...
- pervycreeper 12y agoSlightly OT: is it now possible to run a completely free OS on this new version? I've been getting contradictory info on this so far.
- Narishma 12y agoThat's because completely free means different things to different people. Does it include the firmware/bios? Are you only concerned with what runs on the CPU?
- seba_dos1 12y agoOriginal Raspberry Pi needs user to provide non-free firmware blobs on SD card to even boot the CPU. That's pretty non-free in any meaning I can imagine. It seems like it's still the case with Raspberry Pi 2.
- Narishma 12y agoThe only difference between that an a PC is that the PC stores the firmware blob in a ROM chip while the Pi stores it on the SD card. Both require it to boot.
- morganvachon 12y agoNot yet. Closed source binary blobs are necessary for booting and for accelerated video. In fact, it's the GPU that bootstraps the rest of the board when you first power it up. There is work being done to write an open source driver for the GPU, with the blessing of the RPi Foundation and BSD-licensed code provided by Broadcom[1]. But I don't know if that will include the bootstrapping code, or how far along it is. Given that it is BSD licensed, it may not meet everyone's definition of "Free", but at least there is a good chance of having fully documented, source-available drivers in the future. [1] http://www.raspberrypi.org/a-birthday-present-from-broadcom/ http://www.raspberrypi.org/a-birthday-present-from-broadcom/
- pedrocr 12y ago
- deleted 12y ago[deleted]
- bitwize 12y agoSomeone commented "Fire photon torpedoes..." In light of Heartbleed and Shellshock, I propose calling this the Photon Torpedo vulnerability.
- seba_dos1 12y ago>In light of I see what you did there!
- deleted 12y ago[deleted]
- exDM69 12y agoThis reminds me of an old Finnish engineering legend from the early days of Nokia. The guys had just built an important prototype of some network equipment (early GSM base stations IIRC), which was going to be demonstrated for the press. All tests and previous demos had gone fine. But as soon as the demo for the press started, the machine crashed. The management was upset. Later, the reason was found to be some old EPROM chips that are erased using UV light, and the photographers' cameras had strong flashes that went through the tapes covering the "window" on the chip. This caused the program memory to be corrupted when a photograph was taken.
- teddyh 12y agoInteresting that the Finnish version of this story is about Nokia, GSM base stations and EPROM memory. The version from 1990 from The Devouring Fungus which I quoted in a separate comment is about the IBM 701 and CRT memory.
- mikerr 12y agoThe problem IMO that the chip in question doesn't have a plastic cover, look how shiny it is in this video: https://www.youtube.com/watch?v=c7p2OcQ7G58 https://www.youtube.com/watch?v=c7p2OcQ7G58 A laser (no EMP!) shone on that chip will also crash the Pi.
- agumonkey 12y agoThe new wave of single board computers really exposed me to the amount of failure that can happen at the electrical level. Growing up with large ATX boxes I'd never expect so many things to go wrong. btw: anyone tried to light-freeze other devices (banana, orange, cubie, etc) ?
- IgorPartola 12y agoAs my electronics professor said: "every digital circuit is really an analog circuit."
- mikerr 12y agoHere's a pic of the chip in question (so you can cover it up) https://pbs.twimg.com/media/B9Ut_QwIQAACrp_.jpg https://pbs.twimg.com/media/B9Ut_QwIQAACrp_.jpg
- teddyh 12y agoFrom The Devouring Fungus, Karla Jennings, 1990, chapter 10, The Monster Turns… and Falls to its Knees, p. 211: Another legendary debacle triggered by light hit at a highly publicized affair thrown by IBM, ironic considering that IBM is the master of the seamless image. D. E. Rosenheim, who helped develop the IBM 701, the first mass-produced modern commercial computer, recalled the famous faux pas, which occurred when the company held a dedication ceremony for the 701’s installation at its New York headquarters. Top-level executives, the engineering team, and a gang of reporters crowded the ceremony room “Things went pretty well at the dedication,” said Rosenheim, “until the photographers started taking pictures of the hardware. As soon as the flash bulbs went off, the whole system came down. Following a few tense moments on the part of the engineering crew, we realized with some consternation that the light from the flash bulbs was erasing the information in the CRT memory. Suffice it to say that shortly thereafter the doors to the CRT storage frame were made opaque to the offending wavelengths.” Those who do not know their history are doomed to repeat it.
- BuildTheRobots 12y agoLink for the lazy: http://en.wikipedia.org/wiki/Williams_tube http://en.wikipedia.org/wiki/Williams_tube Note for the kids: Yes, that's right, it says CRT memory. That's the same Cathode Ray Tube as found in non-flat-panel TVs and monitors, except we're using it as a high speed storage device. Ironically, the wikipedia page for Selectron tubes actually has more useful information on Williams tubes than it's article does... http://en.wikipedia.org/wiki/Selectron_tube http://en.wikipedia.org/wiki/Selectron_tube
- wolfgke 12y agoQuestion to HN: Does also the Raspberry Pi 1 B or B+ have this problem or is the Xenon flash problem specific to the Raspberry Pi 2 B? Is somebody willing to do this experiment/has done it?
- AlyssaRowan 12y agoThe B doesn't (at least according to the lovingly-hand-resoldered, first batch board I've got handy). Don't have a B+ to hand, sorry. It might?
- DalekBaldwin 12y agoLooks like there's some truth to the belief that a photograph steals its subject's soul.
- andruby 12y agoAwesome. "Flash" your board just got a whole new meaning :)