Microsoft Windows CE 3.0  

Drivers for Serial Devices

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Windows CE supports two methods of driving serial devices. The first requires you to create a stream interface driver DLL that presents high-level information from the device to applications. The second does not require that you write a driver; instead, it requires the applications that use the device to interpret the device data.

These two methods are possible because serial devices are always accessed through built-in COM ports, generally COM1: through COM3:. With the first method, you implement a serial device driver to present a new device file name to applications, such as COM4: or another file name specific to the function of the serial device. Internally, a device driver uses the services of the built-in COM port to access the peripheral. You can also let user applications open a built-in COM port to access the peripheral device directly.

The following are the factors allowing you to decide between these two strategies: