" #
Under Windows Vista, a composite device with a CDC virtual COM-port
function can use an interface association descriptor (IAD) to identify the interfaces
that belong to the CDC function. Windows can then identify and load
the correct drivers for all of the composite device??™s functions. Figure 16-2
shows the descriptors for an example composite device of this type.
Table 16-7 shows the contents of the IAD as defined in the USB 2.0 engineering
change notice (ECN) Interface Association Descriptors. To inform the host
that the device uses an IAD, the device descriptor should use the values in Table
[DriverService]
DisplayName=%SERVICE%
ServiceType=1
StartType=3
ErrorControl=1
ServiceBinary=%12%\usbser.sys
[Strings]
LAKEVIEW="Lakeview Research LLC"
MFGNAME="Lakeview Research LLC"
DESCRIPTION="USB COM Port"
SERVICE="USB COM-port Driver"
Listing 16-1: An INF file for a generic USB virtual COM port using the CDC
drivers (Sheet 2 of 2).
Using Generic USB Controllers
359
Device
Configuration
Interface
(CDC Communication)
Interface
(CDC Data)
Header
Functional
Abstract Control
Model
Functional
Union
Functional
Call Management
Functional
Endpoint
(Interrupt IN)
Endpoint
(Bulk OUT)
Endpoint
(Bulk IN)
USB standard
descriptor type
Class-specific
descriptor type
Interface
(HID)
Endpoint
(Interrupt IN)
HID
Endpoint
(Interrupt OUT)
Interface Association
Figure 16-2: A composite device that contains a CDC function and a HID function
can use an interface association descriptor to specify the CDC interfaces.
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