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August 18, 2005
Windows Mobile Power States
A good read for CPT 355 about power for Windows Mobile devices
http://blogs.msdn.com/windowsmobile/archive/2005/08/01/446240.aspx
This is part of series on power, but one of the more interesting parts is the list of power states for smartphones and Pocket PCs from this post
http://blogs.msdn.com/windowsmobile/archive/2005/08/10/450186.aspx
* On: The user is interacting with the device. Everything is on.* BacklightOff: There has been a brief period of user inactivity (no one has pressed any buttons or touched a touchscreen). The backlight has been turned off, but everything else is on. When you set the backlight timeout values in the control panel, you're setting how long the system should wait before going into this state. (Note that this state is new for WM 5.)
* UserIdle: There has been a longer period of user inactivity. Both the backlight and LCD have been turned off. When you set the screen timeout value on a Smartphone control panel, you're setting how long the system should wait before going into this state. This state is generally not used on PocketPC. There's no reason to turn the screen off when the device is about to go to sleep (sleeping turns the screen off). However, if/when PocketPCs go to the "Always On" model, they'll start using this state.
* ScreenOff: You go into this state when someone specifically says to turn the screen (and backlight) off. For instance, in Media Player you can assign a button to turn the screen off. When you press it, we go into this state. This state is different than UserIdle, though. This state says, "The user wants the screen off and doesn't want it to turn back on." UserIdle says, "The user hasn't touched any buttons in a while, so we might as well turn the screen off to save power." In ScreenOff, pressing a button (other than the power button) doesn't turn the screen back on. In UserIdle, pressing a button does turn the screen back on. Both PocketPC and Smartphone use this state.
* Unattended: This is a confusing state in which the screen, the backlight, and the audio are off. I won't go into too many details, other than to say that this is a PocketPC-only state that is used by applications which need to do things without alerting the user. While the PocketPC is in this state, the user thinks the device is asleep. For instance, ActiveSync when it syncs every 5 minutes. It's waking up, syncing, and going back to sleep, but the user can't tell.
* Resuming: This is the state the PocketPC goes into when it wakes up from sleep. In this state, the screen is off, and there is a very short (15 second) timer before it goes back to sleep. The only way to keep the device from going back to sleep is to have something put it into one of the other states. This is really for dealing with spurious wakeups and for giving the system a way to get into Unattended without letting the user know about it.
* Suspended: This is the PocketPC "Sleep" state. Everything is off, and the system isn't going to wake back up until some piece of hardware wakes it up. It's not actually an official Power Manager state, the way the other six are, but I'm including it for completeness.
[Update] - BradA has a good link and an interesting stat.
Industry forecasts predict that up to 67% of workforce computers will be mobile PCs.
http://blogs.msdn.com/brada/archive/2005/08/21/PowerManagement.aspx
Posted by mikel at August 18, 2005 06:32 PM
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