Silicon Laboratories Stepper Machine Specifications download pdf (Page 26)

Enumeration: Finding a Driver

 Once all descriptors are communicated, the Windows host searches for

a driver based on the vendor ID and product ID of the device

[DeviceList]

%DESCRIPTION%=DriverI nstall,USB\VID_1ABC&PID_2XYZ

[DriverCopyFiles]

usbser.sys

[DriverService]

ServiceType=1

StartType=3

ErrorControl=1

ServiceBinary = %12%\usbser.sys

Example entries of an INF file

Vendor ID

Product ID

Drivers listed for install

Configuration information

Host looks for driver info in the INF File:

• Host tries to match the Vendor ID

• Host tries to match Product ID

• If possible, host tries to find the Release number

If the Windows host can’t find a matching INF file it will prompt for

the user to select a location where the files can be found for install

Remember that two of the fields in the device descriptor are the Vendor ID (VID)

and the Product ID (PID). The first descriptor the host will request is the device

descriptor and as such it will know what device it is communication with. The

Windows operating system (OS) will be able to search an inf file to see if it can find

a match between the VID and PID and what was received. If a match is found then

the driver that the OS needs to install will be called out and the OS can start it. If a

match is not found then the OS will prompt the user to find the driver to load. This

slide shows some excerpts from an INF file and is provided to show what the host

would be looking for in order to get the device up and running. In this case, a CDC

class device using the usbser.sys driver.

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Silicon Laboratories Stepper Machine Specifications Page 26