The pnpports
example demonstrates a class installer and property page provider for the Ports
class. The devcon example shows how to obtain information about installed
devices and how to perform functions such as enabling, disabling, restarting,
updating drivers for, and removing devices.
COM Ports on PCs
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Windows uses several methods to detect COM ports:
For internal Plug-and-Play ports, the serenum.sys driver retrieves a PnP ID from
the port. The PnP ID contains manufacturer and product identifiers and other
optional information. Microsoft??™s Plug and Play External COM Device Specification
defines the protocol for retrieving the PnP ID.
For legacy (non Plug-and-Play) ports, the serial.sys driver reads port settings
from the system registry. The settings are in a COM port subkey under ..\Services\
Serial\Parameters.
For USB virtual COM-port devices, a USB driver requests a series of data structures
called descriptors from the device. The descriptors contain information
that identifies an INF file. The INF file names the device??™s driver, which determines
how application access the device.
For COM ports on serial servers, COM-port redirector software creates and
installs virtual COM ports on the PC.
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COM-port software can use two Globally Unique Identifiers (GUIDs) to find
and gain access to devices. A GUID is a 16-byte value that can identify devices
that behave in similar ways.
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