|This is retired content. This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This content may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist.|
Windows CE 2.10 and later support the following USB features:
Windows CE supports enumeration of USB devices on the bus. The bus enumeration process is a multistep query sequence: the HCD module acquires information from a connected device, assigns it a unique USB address, and sets a configuration value. Once enumeration is complete, the device is configured and ready to conduct, transmit, and receive transactions. At this point, the USBD module attempts to load one or more USB device drivers to control the device, based on the information contained in the device and interface descriptors. If no suitable driver has been registered for the device, a user is prompted to enter the name of a driver to control the device.
Windows CE provides support for bus-powered and self-powered devices. For both types of device, the USBD module reads the power requirements of the device from the descriptor information and rejects the device if it exceeds the maximum power threshold. OEMs can set the current-draw limit, so IHVs should not rely on any particular amount of available current, except as detailed in the Universal Serial Bus Specification, Revision 1. Current-draw limits are enforced by USB hubs, not by the host computer; devices which draw too much current will be shut down by their hub. Hubs that cannot control the power level on individual ports may simply shut down all their ports, or may be forcibly shut down by an upstream hub, when a current over-draw situation occurs. This can cause multiple USB devices to disconnect from the bus if a single device draws too much current.
Windows CE does not support complex power saving modes or partial-power modes for USB devices when the Windows CE device is suspended. Instead, the entire bus is shut down. Consequently, Windows CE does not support resuming from suspension in response to the needs of a USB device. Also, Windows CE does not support the remote wakeup feature as described in the Universal Serial Bus Specification, Revision 1.
Windows CE supports all four types of data transfer defined in the Universal Serial Bus Specification, Revision 1. USB device drivers can use any of the transfer types that are appropriate for their peripherals.
The USB architecture implemented in Windows CE supports loading class drivers. Examples of USB device classes include the human input device (HID) class and the mass storage class, among others. OEMs or IHVs can write their own class drivers and load them appropriately, using the registry mechanism.
Windows CE 2.12 and later supports the following features:
Windows CE offers limited support for the following features:
Last updated on Tuesday, July 13, 2004