[gta02-core] component hunt: some results

Werner Almesberger werner at openmoko.org
Thu Apr 8 00:19:55 CEST 2010

?lvaro Lopes wrote:
> Depends a bit on what we do want - just a 5V, 500mA-limited power supply ?

Yes, 5 V, limited to something close to 500 mA, with an active-high
enable input, and shouldn't act up if disabled and there's a voltage
on the output.

I've listed a few candidates in bom/research/u4904. Perhaps the
ADP2503ACPZ-5.0-R7 wouldn't be all bad. Would be good if someone
could check that I haven't overlooked anything that could cause

> Hard. Those are typically short life components, maybe we should just
> replace them with similar (on purpose) parts. PMU should be fairly easy,

Whoa ! I should frame this, nail it to the wall, and show it to any
Openmoko veteran who comes visiting ;-)

You have no idea of the amount of suffering that went into finding a
suitable PMU and getting it to do what we want. In part it's due to
the somewhat quirky structure of this PMU, with mask-programmed reset
behaviour, but a lot is also just discovering all the corner cases.

It's already quite a ride to make sure the right rails come up with
the right voltage at the right time to get the CPU out of reset,
while making sure that each of these rails has a suitable current
rating, and no other rails are doing anything evil (such as feeding
too high a voltage into some component or subsystem) while the CPU
is still rubbing its eyes.

Naw, I'd be very afraid of changing the PMU.

Changing GPS is also tricky. It may be an option, but any new design
is likely to come with a lot of changes, so I'd rather avoid this,

Of course, if you have some specific components in mind with
sufficiently open documentation, good availability, no need of new
drivers, etc., then it can't hurt to have a look at them. I would
still be very reluctant to change the PMU, even to a different
variant of the PCF50633, because one small slip may mean that the
board never even starts to run, but we can take larger risks with
less critical subsystems.

> I hope so too. And time to revive gta02-core blog. I believe we do
> have again enough stuff to put there.

Whee ! We have press coverage again ! :-)

- Werner

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