Syncing your device in the background requires that your user has approved background syncing by your app.Your device must also be connected to or paired with the PC, with active I/O, and is allowed a maximum of 10 minutes of background activity.More detail on policy enforcement is described later in this topic.
If your app is associated with device metadata, that Windows Store device app can also use a device background agent to perform device updates, such as firmware updates.
Device background agents are subject to policies that ensure user consent and help preserve battery life while devices are being synced and updated.
To perform device sync and update operations, create a device background task that uses the Device Use Trigger and Device Servicing Trigger, respectively.
When this happens, without the help of a device background task, any ongoing device operations like syncing and updating will be interrupted.
Windows 8.1 provides two new background task triggers that let your app perform long running sync and update operations on your peripheral device safely in the background, even if your app is suspended: Device Use Trigger and Device Servicing Trigger.
For more info about app suspension, see Launching, resuming, and multitasking.Enables long running sync operations to or from your peripheral device while your app is suspended.To learn how this is done with the Custom USB device sample and the Firmware update USB device sample, see Creating a device background task.Note Windows Runtime device APIs don't require device metadata.That means your app doesn't need to be a Windows Store device app to use them.Windows Store apps can use these APIs to access USB, Human Interface Devices (HID), Bluetooth devices, and more. When users move your Windows Store app off-screen, Windows suspends your app in-memory. When an app is suspended, it is resident in-memory and Windows has stopped it from running.