Here's a pic of the chip in question
(so you can cover it up)
https://pbs.twimg.com/media/B9Ut_QwIQAACrp_.jpg
A Xenon flash will cause the Raspberry Pi 2 to freeze
101–110 of 135 posts
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#102From 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.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#103Earlier quoted context omitted.
What about glass, then that should work, right?
Not sure I understand you correctly. The problem should happen with near-infrared, visible, and UV-light. Glass is transparent in the visible range, and depending on type, also in IR / UV, so glass won't work as a shield. The easiest, reliable way to shield would be wrapping in aluminum foil (also helps against RF-interference).
Yeah you are right. I was assuming that the chips would block visible light but I forgot about UV.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#104Question 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?
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#105Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#106Slightly 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.
That'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?
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#107Slightly 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.
Not 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/
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#108Earlier quoted context omitted.
Are 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?
Alright I put the Pi 2 in a cardboard box and held the flash at the same spot (but the box obscures the light). It keeps running just fine and doesn't have the nasty spike. Definitely is something light related.
I'm not familiar with the photoelectric effect - would this be susceptible to a laser (and if so, how weak a laser? A laser pointer?)?
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#109Earlier quoted context omitted.
So this would be easily rectified by using a case for the pi?
A case would fix it, but a cheaper fix would be to just put a dab of nail polish or other lacquer on chip U16, which seems to be the culprit.
Handy tip! Which - just tested - seems to work for me, at least with a couple of coats of black nail polish, and double-checked with a high-end Canon flash and a random green laser pointer. (Of course your mileage, and nail polish, may vary.)
I should change the hostname to nemi. ;)
There's another 'shiny' chip on the board too, next to the HDMI port, U8 I think, but it doesn't seem to give a damn what you do to that.
Compared to having to resolder all the Ethernet ports by hand, or USB power issues, this is a pretty minor errata! I presume the factory will pop a blob of epoxy on it for future runs, if they can't get this chip with a package on it.
Re: A Xenon flash will cause the Raspberry Pi 2 to freeze
#110Question 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?
The 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?