Disable sleep mode in Windows Mobile 6

Question

Hi,

Does anyone know how could I programatically disable/enable sleep mode on Windows Mobile?

Thanks!

Answer 1

Probably by modifying the "System Power States" as described here (but in c#)

That article also describes a way to prevent the mobile device to sleep (which is not exactly what you may want), by calling the native function SystemIdleTimerReset() periodically (to prevent the device from powering down).

Answer 2

Modify the Power Manager registry setting that affects the specific sleep condition you want (timeout, batter, AC power, etc) and the SetEvent on a named system event called "PowerManager/ReloadActivityTimeouts" to tell the OS to reload the settings.

Answer 3

If you want your program to not be put to sleep while it's running, the best way is to create a KeepAlive type function that calls SystemIdleTimerReset, SHIdleTimerReset and simulates a key touch. Then you need to call it a lot, basically everywhere.

#include <windows.h>
#include <commctrl.h>

extern "C"
{
    void WINAPI SHIdleTimerReset();
};

void KeepAlive()
{
    static DWORD LastCallTime = 0;
    DWORD TickCount = GetTickCount();
    if ((TickCount - LastCallTime) > 1000 || TickCount < LastCallTime) // watch for wraparound
    {
        SystemIdleTimerReset();
        SHIdleTimerReset();
        keybd_event(VK_LBUTTON, 0, KEYEVENTF_SILENT, 0);
        keybd_event(VK_LBUTTON, 0, KEYEVENTF_KEYUP | KEYEVENTF_SILENT, 0);
        LastCallTime = TickCount;
    }
}

This method only works when the user starts the application manually.

If your application is started by a notification (i.e. while the device is suspended), then you need to do more or else your application will be suspended after a very short period of time until the user powers the device out of suspended mode. To handle this you need to put the device into unattended power mode.

if(!::PowerPolicyNotify (PPN_UNATTENDEDMODE, TRUE))
{
    // handle error
}

// do long running process

if(!::PowerPolicyNotify (PPN_UNATTENDEDMODE, FALSE))
{
    // handle error
}

During unattended mode use, you still need to call the KeepAlive a lot, you can use a separate thread that sleeps for x milliseconds and calls the keep alive funcation.

Please note that unattended mode does not bring it out of sleep mode, it puts the device in a weird half-awake state.

So if you start a unattended mode while the device in suspended mode, it will not wake up the screen or anything. All unattended mode does is stop WM from suspending your application. Also the other problem is that it does not work on all devices, some devices power management is not very good and it will suspend you anyway no matter what you do.