next-generation MPU discussion

Werner Almesberger werner at
Fri Apr 25 18:39:46 CEST 2008

joerg at wrote:
> Remove connections? Never! Maybe remove a whole layer, so it's worth it, but 
> some connections... :-/

Heh, you gotta start somewhere or that layer will never come off ;-)

> We have to plan for _some_ maximum. 64? 256? Drop some of them later no 
> problem. This is our core-design!

Hmm, one of the many early design proposals looked like Suzhou at night
(think Las Vegas, just better illumination), so I suspect the "worst
case" number of LEDs may be relatively large. However, we may equally
well go in the opposite direction, and just not have all that glitter.
This is really a decision that will eventually come from our designers.

If *I* was designing a phone in a shape similar to GTA01/02, it would
have between zero and one strategically placed dual- or tri-color LEDs
for indications, plus however many single-color LEDs it takes to
illuminate the buttons at night. I also find it difficult to imagine
doing something other than a pure gimmick in such a phone with more
than 6-8 effectively placed LEDs.

So I'd say 16 "soft-PWM" channels (that's 2 channels per dual-color
LED, 3 for a tri) should be plenty and 8 still very reasonable. But
don't kill me if they end up wanting a 100x100 matrix, each LED with
its own hardware PMW ;-)

As usual, it's safer to err towards having too many pins than too few.
If we end up not using some or all of them, we can still try to just
run them to test points and let other people figure out some use for

- Werner

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