Battery charge while powered "off"


doragasu

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Jun 2, 2008
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One of the few things I don't like about the Pandora, is that you cannot charge the battery while the console is powered off. So when I want to charge the console, I turn it on, plug the charger and then put the device in suspension. This works, but feels a little weird.

I know the console must be powered on to charge, because the CPU is needed to monitor the charge process, as happens with most smartphones. But again like happens with smartphones, I'd like that if you plug the charger while the unit is off, instead of booting to the full OS, the console would boot a small image showing the battery charge icon (and maybe the battery level) for some seconds, and then completely blank the screen (until a key is pressed or the console is powered on), faking the power off state.

Is this going to be implemented?
 
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As you said, it is like this with most smartphones. There is no difference to closing the lid and charge it to any boot to small os.


what would really be the difference?


What could be easily implemented would be some program that you can start and then it shows the batterystatus while everyzhing else is powered down, den shuts the Pandora down when the charger is disconnected.


But I really don't see the point in that.
 
Actually most phones are powered on when you charge them it just goes into charging only limited bootup mode.. the Pandora just lacks this mode.. The Pandora is capable of handling this, It never was implemented because there are so many other more important things that needed to be done on the OS and it never seemed like an important matter to resolve.
 
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Actually most phones are powered on when you charge them it just goes into charging only limited bootup mode.. the Pandora just lacks this mode.. The Pandora is capable of handling this, It never was implemented because there are so many other more important things that needed to be done on the OS and it never seemed like an important matter to resolve.
Just an impression I have: The number of request for a special charge mode dropped after proper powersaving was implemented, and most people did not power off their Pandora anymore
 
So it looks like I'm alone in this request :(

It's not a real problem, I suppose I can live with it. But it feels a bit weird when you plug the charger at night before going to sleep, and instead of "just charging", it boots the full OS. For me it makes a lot more sense to boot a small image that only shows the battery charge animation for a few seconds and then blanks the screen (pretending to be "off" even if it is not).
 
So it looks like I'm alone in this request
You aren't alone, it's just not a major priority.
For me it makes a lot more sense to boot a small image that only shows the battery charge animation for a few seconds and then blanks the screen
It does make more sense, but doing that isn't really easy. It would definitely be a very nice to have feature, especially on the Pyra which is going to have more RAM and by that almost certainly have an unfortunately lower standby time (unless we can also get a proper deep sleep, suspend to disk mode) but unless someone with the skill to code such a thing also has an interest in doing it there's no point in worrying about it.
 
You will have another problem:


when you really want it to boot, it will still boot to the charging os if you plug in the charger before flipping the powerbutton.


You would need some way to detect at boot if it should load the whole os or not.


Maybe it could boot (or continue to boot) if you press some key while charging.


Is there a way to check if the charger is connected by checking some file in /proc or something?
 
What about adding extra circuitry that can manage charging while the CPU is powered-off?  Not worth the expense perhaps?
 
when you really want it to boot, it will still boot to the charging os if you plug in the charger before flipping the powerbutton
That's not really a problem. If it's in charging kernel, if it detects the power switch it just continues with the normal boot.It is possible to poll the power chip to know why it was turned on, either because power was applied, switch was hit, an interrupt was triggered, or an alarm went off.

What about adding extra circuitry that can manage charging while the CPU is powered-off?  Not worth the expense perhaps?
About as hard as adding a micro kernel I would suspect, and more prone to failure.
 
You will have another problem:

when you really want it to boot, it will still boot to the charging os if you plug in the charger before flipping the powerbutton.

You would need some way to detect at boot if it should load the whole os or not.

Maybe it could boot (or continue to boot) if you press some key while charging.

Is there a way to check if the charger is connected by checking some file in /proc or something?
What about just always booting to the charging os when the charger is plugged in. If lid closed, screen is off. If lid opened, show a message like "Charging - press any key or power switch to boot" or something of the like.
Then I wonder what such a charging os could be. Would it already boot a minimal Linux kernel? Or could some small standalone binary save even more power in some way?
 
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doesnt the pandora use less power while charging based on its components when in low power mode since all the power hungry things on it are shut off, while ive seen phones that even keep the most power hungry LCD on while charging? plus, wouldnt adding a charging kernel just remove the option on some to run off charger alone without battery?
 
plus, wouldnt adding a charging kernel just remove the option on some to run off charger alone without battery?
In addition to knowing what caused it to boot, the power chip can be polled for whether a battery is present or not. The boot kernel, whatever it may be, just needs to say "did I start from AC, and is there a battery present? If yes and yes, go to charge kernel, else go to full kernel"
 
Personally I'd hate such feature, it would make rebooting the device remotely impossible while plugged (which is almost always the case for me) and would only add another thing to skip when you boot with a charger. It's really annoying when my phone does that, instead of plugging and leaving it to boot and minding other things I have to wait like 10s until it shows it's battery animation, and then after pressing power several times it finally continues to boot.

Before someone says that reboot can be detected, IIRC pandora's PMIC can't distinguish that, it would need some nasty hacks like putting value in RAM and hoping it'd survive reboot (which isn't guaranteed) and then going into charge thing (or not) based on that.

Why do people want this "feature"? It sucks!

What about adding extra circuitry that can manage charging while the CPU is powered-off? Not worth the expense perhaps?
It was at least considered for Pyra at one point, I'm not sure what the current status is.For pandora, it's way too late to change hardware things.
 
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How about as a compromise, some magic button combination during to put it into charge mode? Or bring up some kind of boot menu which you can select it from?

But I don't really see the point either, when the device uses so little power when idling in a normal state.
 
it would need some nasty hacks like putting value in RAM and hoping it'd survive reboot (which isn't guaranteed) and then going into charge thing (or not) based on that
Could set an unused voltage register, like VAUX3_CFG_VOLTAGE (at least I think vaux3 is unused): if powered on it gets reset to default: if there is a soft reset it is untouched; if a warm reset occurs at the PMIC level it can be controlled to reset or not. I'm not sure how the Pandora handles a reset, whether it triggers a NRESWARM or simply restarts the PC back at 0 or something.But that's all academic, it's a hack like you say, and even if we could hack something together I'm still not sure it's worth it.
 
As someone who's usually not using his Pandora when turning it on by plugging in the charger, I'd have another suggestion which shouldn't be too hard to do:
How about option (preferably disabled by default) to directly go into low-power mode after booting if the charger is plugged in? 

That way one wouldn't have to wait for the device to finish booting just to flip the switch then. While booting is done reasonably fast, it would be nice to just plug in the cable and forget about it.
 
What is low-power mode? There is barely any difference between lid-closed-idle and suspend-to-ram, at least on the Pandora.

Random question: is there a way to save power by shutting down most of the ram? It would be neat if you could power only, say, 256MB of ram as long as you don't use more than that. But I have no idea if that is feasible.
 
There is barely any difference between lid-closed-idle and suspend-to-ram,
With the lid closed, my Pandora loses about 2% per hour. In suspend to RAM it only loses about 1/2 a percent per hour. At least in my tests, that's a difference of a few days vs a full week before it needs to charge.
 
I'm completely ignorant about such things so be gentle! How do Nintendo handhelds (GBA, DS, 3DS etc.) cope with charging while turned off and booting while plugged in? Could the Pyra not do something similar?
 
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