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Consequences from Atmel removal of full-swing crystal oscillator #10

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cefn opened this issue May 3, 2016 · 0 comments
Open

Consequences from Atmel removal of full-swing crystal oscillator #10

cefn opened this issue May 3, 2016 · 0 comments

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@cefn
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cefn commented May 3, 2016

A collaborator noted this change to the ATMEGA328 architecture...
http://hackaday.com/2016/05/03/atmel-removes-full-swing-crystal-oscillator/
...and was speculating if our recommended layouts at http://shrimping.it might fail with the new chips.

We have been relying on OptiLoader to flash chips since we began, and would ideally carry on doing so for reliability. Can you comment if the fuses set by Optiloader would make the newer-architecture chips flashed in this way vulnerable to a change in behaviour?

Ideally our 'Minimal Shrimp' layout would continue to behave as it always has...
http://start.shrimping.it/project/shrimp/build.html

We, like many in our teaching workshops, are taking shortcuts with Crystals unsupported by the 22pF caps (although we always ship the caps in case people need to replicate the Uno circuit more faithfully as part of http://start.shrimping.it/kit/shrimp.html so that a 'Protected Shrimp' build can be followed http://start.shrimping.it/project/protected/index.html ).

While we have proven this to be effective both in teaching and in deployment, I am a little concerned that if the hardware itself changes, then there may be knock-on effects.

I think I gather from this...
http://www.avrfreaks.net/comment/1476106#comment-1476106
...that the canonical setting for the Uno's crystal when configured for Optiboot is Low Power, not Full-swing, and this would suggest we would be unaffected as we don't rely on that feature of the architecture anyway.

Am I right?

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