Errors Communicating with USB Printers due to USB Selective Suspend

Source: Microsoft Support

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If you have a printer connected to your computer through a Universal Serial Bus (USB) connection, communication with the printer may fail intermittently with a variety of possible error messages.

This problem may occur due to the�action of�USB Selective Suspend.� When the USB Printer is placed in a USB Suspended state due to inactivity, some delay may occur in processing new requests while the USB Printer resumes from the USB Suspended state.� This delay may cause communication requests to the printer to time out and fail with an error status such as error 21 (ERROR_NOT_READY).

If a request to a USB Printer fails after the printer has been idle for some time, retrying the request quickly may succeed.

Developers of drivers for USB-connected printers may be able to work around this problem by using one or a combination of the following actions:

1. If a call to the USB port monitor (for example, pfnWritePort())�returns Error 21 (ERROR_NOT_READY), retry the call after a short delay (to allow time for the USB device�and hubs to fully resume).

2. In your language monitor (or other module) open a handle to the USB printer port and keep it open to prevent the USB printer from entering Selective Suspend.

You may also be able to work around this problem by disabling USB Selective Suspend for the Windows installation where you are experiencing this problem.

For detailed information on how to disable USB Selective Suspend functionality, please see the following article in the�Microsoft Knowledge Base:

902274�A device may not establish a connection with a desktop computer when you try to connect the device to the desktop computer through an external USB port hub in Windows XP or in Windows Server 2003

On Windows XP and Windows Server 2003, the Microsoft USB Printer class driver (Usbprint.sys) implements USB Selective Suspend functionality.� Usbprint sets the printer to Idle status if there are no handles open to the USB printer port, which may cause the USB printer to enter the USB Suspended state.� When port-monitor calls are made while the printer is suspended, the port monitor times out the request sooner than the printer and intervening hubs can resume from USB Suspended state, and returns Error 21 (ERROR_NOT_READY).

This problem does not occur on Windows Vista, Windows Server 2008, and later versions of Windows, because the version of Usbprint.sys included with these Windows versions does not implement USB Selective Suspend functionality.

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