Windows® 2000 Device Driver Book: A Guide for Programmers, Second Edition, The

Code Example: A Timer-Based Driver

This modified version of the parallel port driver disables interrupts and uses a CustomTimerDpc routine to transfer data at fixed intervals. The code for this example is included on the companion CD and on the companion Web site, http://www.W2KDriverBook.com.

Device Extension Additions

The Device Extension is modified to include the DPC and Timer objects, plus a polling interval value, stored in microseconds.

 typedef struct _DEVICE_EXTENSION { ... KDPC pollingDPC; // reserve custom DPC object KTIMER pollingTimer; // and the Timer object LARGE_INTEGER pollingInterval; // timeout counter // in us ... } DEVICE_EXTENSION, *PDEVICE_EXTENSION; // Define the interval between polls of device in us // 100 us #define ...