Tuesday, February 10, 2015

Raspberry Pi 2 has a photosensitivity bug

The new and improved Raspberry Pi 2 is way better than its predecessor, but it comes with an unexpected "feature" (as in: bug) that makes it camera shy. If you take pictures with a Xenon flash or shine a laser on it, it may very well turn off instantly.

The effects of light on integrated circuits aren't nothing new (just ask those people that used to saw off transistor caps to turn them into photo-transistors capable of measuring light intensity; not to mention solar cells) and that's why integrated circuits usually come encapsulated in plastic, with just the pins sticking out.

But on Raspberry Pi 2 there's a tiny unprotected circuit, a WL-CSP chip that has no encapsulation underneath, to make it slimmer and cheaper, and is responsible for managing the power to the main SoC chip.

This means that a badly placed camera flash or laser light might shine through under it and cause it to reset the system. This only happens with particular light sources, such as Xenon flashes or lasers; and it can easily by "fixed" by applying something around the chip to make it "light-proof" (or just sticking your RPI2 inside an opaque case, which will be the norm.)

Anyway, just be prepared should you use your RPI2 for a paparazzi-proof device...

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