My Gta02s wont charge / chgena = 0 by default

Andy Green andy at
Mon Jun 23 09:12:48 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:

|> | It is utterly nonsense to intentionally disable battery charging in
|> any time
|> | whatsoever.
|> In itself it's perfectly sane to tell the charger to standby if there is
|> no power coming in.
| No it isn't at all (if switching off PMU-charge-battery path is what
| talking about). This function HAS TO BE ENABLED all the time (see your
| statement below). In the end what's the use of disabling charging when we
| have no power to do charging anyway - it will be implicitly disabled and
| comes back as soon as there is any power left over (besides powering the
| system) to do so. See PCF50633-manual!

"In itself" means local to what I wrote... a generic charger with no
power coming in can be put to standby because what else will it do with
no power?  So that is generically a sane proposition.  I wrote that
because you said: ''It is utterly nonsense to intentionally disable
battery charging in any time whatsoever.''  For the pcf50633 case, I
don't think you are ready to be so certain either, because when I look
at MBCC1 reset state for our variant, I see it wakes up with chgena = 0,
so the manufacturer disagrees with you.

|> What makes the trouble is the setting is sticky
| that's an *option*, no trouble!

Werner seems to blame chgena being sticky in suspend for the failure to
charge issue if I read him right (and it sounds right).

As for "option" you have to take care.  There are many registers which
have a notation "this register is reset in NoPower state".  Because of
the privileged position of pcf50633 in the power handling, there is a
possible deadlock here where the default state of pcf50633 registers
after NoPower does not suit us.  And the CPU being down then, with no
other intelligence up, we have no control over that to modify it.
NoPower comes when we not only have no power externally or in main
battery but the backup battery is down too.  Other registers reset in
standby.  It's a maze.

If you look at MBCC7 in the datasheet and our variant data, there is no
option here.  In suspend mode usbdevstat gets forced to 01 == 500mA.
chgena is sticky in suspend and set = 0 in NoPower.  No option.

|> there is no always-on intelligence to reassess the situation when power
|> does come
| Sure there is: inside PMU!


|> Instead what we're left with is trying to find
|> a way through the maze of default fixed behaviours of the PMU and trying
|> to match them with what we need.
| No, we are actually building our own mace by disabling PMU-bat-charger,
| instead of simplifying things by just make (as) sure (as possible) it's

I hope the other notes in this email make it clear we have little or no
control over those actions, the variant decides it for us.

| I'll have a closer look in this tomorrow, to name the correct
| and values we need for them with our actual GTA02-battery.

We should be cautious about asserting mastery of the pcf50633: let's
qualify our understandings until we proved it (and proved that we proved
what we think we proved, since there are many settings floating about).
~ It's stung me a few times with letting myself think I understood the
whole shebang only to realize I missed out on a whole layer of stuff
going on quietly in there.  One thing is for sure we are at its mercy
when no intelligence is up to control it, the pcf50633's default
settings are master of our device.

- -Andy
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