USB composite Device instance IDs

I am developing a USB composite device. The composite device have 8 switches and one LED.

When I plugged the Composite device to PC,I could find five devices (each with same device ID but different instance IDs) in开发者_StackOverflow中文版 the HID section of Device Manager.

Why OS is showing multiple instances instead of One. Can anyone help me understand the concept?

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As I recall 'composite device' is just a name in windows to mark that you have multiple devices on your USB line. There isn't a composite device class in the USB protocol. When you connect your USB device to your PC it communicates with all the devices contained in it and reports individually all their address and types. If you are missing some devices in your device manager it could be a driver issue or the device itself is broken. I don't know for sure but maybe there is a limit lower then it could be in theory in the windows hid host driver for the number of supported devices on a single line.