How to: Prevent Automatic Power Down

Article
08/28/2006

You can override the automatic suspend that occurs when no user input has occurred for a period of time. To prevent automatic power down, call the Windows CE SystemParametersInfo function for each of the three time-out values, SPI_GETBATTERYIDLETIMEOUT, SPI_GETEXTERNALIDLETIMEOUT, and SPI_GETWAKEUPIDLETIMEOUT, as shown in the following code. Your application must call the SystemIdleTimerReset function more frequently than any of the nonzero time-out values.

DWORD batIdle, acIdle, wakeUpIdle, shortestIdle;
TCHAR szOutput[200];

// Get the values.
SystemParametersInfo(SPI_GETBATTERYIDLETIMEOUT,0,&batIdle,0);
SystemParametersInfo(SPI_GETEXTERNALIDLETIMEOUT,0,&acIdle,0);
SystemParametersInfo(SPI_GETWAKEUPIDLETIMEOUT,0,&wakeUpIdle,0);

// Determine which is the lowest nonzero value.
shortestIdle=batIdle;
shortestIdle=((acIdle>0)&&(acIdle<shortestIdle)) ? acIdle : (((wakeUpIdle>0)&&(wakeUpIdle<shortestIdle)) ? wakeUpIdle : shortestIdle);

if (shortestIdle==0)
    // If all values are zero, the device can never time out.
    wsprintf(szOutput,_T("Battery Idle Timeout: %d\nAC Power Idle Timeout: %d\nWakeup Idle Timeout: %d\nThe device will not time out."),batIdle, acIdle, wakeUpIdle);
else
{
    // Otherwise, you need to reset the idle timer more
    // frequently than the lowest time-out value.
    wsprintf(szOutput,_T("Battery Idle Timeout: %d\nAC Power
        Idle Timeout: %d\nWakeup Idle Timeout: %d\nYou need to 
        call SystemIdleTimerReset at least every %d 
        sec"),batIdle, acIdle, wakeUpIdle, shortestIdle-1);
}
MessageBox(hWnd,szOutput,_T("Results"),MB_OK);

How to: Prevent Automatic Power Down

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