Airbnb's preferred smart lock vendor accidentally bricks 500 door-locks

Re:Airbnb's preferred smart lock vendor accidentally bricks ... by ChuckMcM on Monday August 14, 2017 @02:31PM (#15011182)

In hindsight I'm sure they will do something different. For folks who are maintaining systems with OTA updates that can't survive an OTA failure, hopefully they now realize they are in the middle of a train wreck and should get to work.

An 8 MB (64 megabits) SPI flash chip[1] is about $2. Two jumpers to power the SPI flash and set the boot/load option is another 3 - 4 cents. These take up less than 30 sq mm of board space. And they give you a tremendous back up in case of failure.

[1] http://www.mouser.com/Semiconductors/Memory/Flash-Memory/_/N...

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Re:Airbnb's preferred smart lock vendor accidentally bricks ... by danellis on Monday August 14, 2017 @04:36PM (#15012613)

If you're using external flash rather than on-die flash, doesn't that mean you'll have to copy it into RAM before running it instead of running it directly, and therefore more RAM will also be part of the extra cost?

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Re:Airbnb's preferred smart lock vendor accidentally bricks ... by ChuckMcM on Monday August 14, 2017 @04:47PM (#15012710)

That depends of course.

All of the ARM chips I'm playing with these days have a serial boot loader in ROM that you can get to by setting a pin on the CPU and powering it up that way. In such a scenario it would take no extra parts.

I believe they emulate or copy the system used by FPGAs to read a configuration from a dedicated SPI chip. Its well understood and a lot of tools can program the SPI chip to have the right sequence of bits in it to do the right thing.

If I were designing a system with OTA updates, then I would design something like this with it for this very reason.

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