Detecting USB power state

Question

Windows has the option of powering down certain peripherals, such as USB ports, to save power (this behavior can be enabled/disabled via Device Manager). The power down happens under various conditions such as when the lid of a laptop is closed. This is causing a problem for me as I have a GUI which talks to hardware attached to the USB port and communications are severed every time the laptop lid is closed. Is there a way to programmatically detect this power-down (standby?) event before it happens and more gracefully shut down my USB device? Is there a way to programmatically configure each of the system’s USB ports to disable this behavior?

Right now I'm looking at SystemEvents.PowerModeChanged, is this the right event to detect this?

Answer 1

It sounds like you want

1. WM_POWERBROADCAST (http://msdn.microsoft.com/en-us/library/aa373247(v=vs.85).aspx)
2. RegisterPowerSettingNotification (http://msdn.microsoft.com/en-us/library/aa373196.aspx)

You first need to call RegisterPowerSettingNotification then WM_POWERBROADCAST messages will be received by your application.

This page has a c# implementation of a power management class using these window messages. http://www.koders.com/csharp/fid00BAA34B0CAA3E320F9F5A44610A015973BF28ED.aspx?s=nativemethods#L175