Lucent Technologies manual USS-720 USB Port Monitor, Description, Application Note February

Application Note

February 1999

USS-720

USB Port Monitor

Description

A port monitor is responsible for the communication between the Windows* spooler and a printing device. It controls the I/O port to which the physical printer is connected and is responsible for the communication channel between the spooler and the print device.

Typically, the port monitor communicates with base I/O drivers (e.g., serial and parallel drivers) for device I/O, but it may also call different interfaces, such as Windows sockets, SCSI, USB, etc.

Note: For more specifics on the Windows spooler and port monitors, see the Windows 95/98 DDK documentation.

The USB Port Monitor, developed by In-System Design, enables printing from Windows applications using the ISD USB Smart Cable. It is included in the USS-720 Evaluation Kit to demonstrate a functional use of the USS-720 device. Figure 1 shows how the USB Port Monitor is included in the Windows spooler.

The USB Port Monitor is installed during the Plug and Play installation of the ISD USB Smart Cable. At initialization, the spooler calls the USB Port Monitor to obtain a current list of USB ports available on the host. Once initialization is complete, the spooler has a record of which USB ports exist, and which printers are associated with each USB port. When the spooler determines that a particular spooled job can be printed, it calls the USB Port Monitor to perform the following:

■Notify the start of the print job,

■Send data to be written to the printer,

■Request data to be read from the printer, and

■Notify the end of the print job.

For a description of the data and control flow in and out of the USB Port Monitor, please refer to the Design and Implementation Notes of the Windows 95/98 DDK.

* Windows is a registered trademark of Microsoft Corporation.

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