next-generation MPU discussion

joerg at joerg at
Sat Apr 26 16:42:52 CEST 2008

Am Sa  26. April 2008 schrieb Werner Almesberger:
> joerg at wrote:
> > Remove connections? Never! Maybe remove a whole layer, so it's worth it, 
> > 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,

GTA04 probably will be quite different

> 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 ;-)

So for this *I* would suggest an I2C device with it's own driver inside, maybe 
a modified dot-matrix-dislay

> As usual, it's safer to err towards having too many pins than too few.

That's why I ask :-)

> 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
> them.

YEP. Thanks for this. We'll make a plan for something from 16 to 64 diodes, 2 
or 3 color each. Depends on MSP430 I think.


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