AN721 datasheet(2/45 Pages) SILABS

2 / 45 page

AN721

Rev. 1.2

2. Basic Device Customization

The steps to customize the CP210x family of devices is slightly different than customizing the CP211x and CP2130

devices. The CP210x devices require a driver, but the CP211x devices do not because they are of the HID class,

which is natively supported by most operating systems. The next two sections describe the recommended steps for

customizing the device based on the family, either the CP210x, CP211x, or CP2130.

2.1. Summary of Steps for Customizing the CP210x Non-HID USB Devices

The CP210x family of devices provides communication from USB to UART. This requires a driver to interface to the

device. There are two types of drivers provided. One is the Virtual COM port (VCP) driver which allows the device

to appear to the PC’s application software as a COM port. This driver is always used first to connect to the Device

Customization Software program to change the PID since by default this driver has the same VID and PID as what

is programmed in the default devices. After the Device Customization Software program is used to change the PID,

the driver must match the new values that have been loaded in the device from the Device Customization

Software. If the user wants to communicate to the device via a high level application program, a USBXpress driver

can be used which provides this functionality. This driver must be downloaded and installed after using the Device

Customization Software. Then the USBXpress driver or VCP driver (which ever one will be used) should be

updated to make sure the driver matches the VID and PID in the device. A PC cannot have both the VCP and

USBXpress drivers loaded with the same VID and PID, as this would cause USB device identification conflicts. In

the end, only one driver can be used, either the VCP or the USBXpress.

There are VCP and USBXpress drivers for various operating systems, which are all listed on the website at



http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx

for

the

VCP

driver

and

www.silabs.com/usbxpress for the USBXpress driver. The process described below must be followed each time a

new operating system must be supported. If the driver has been certified for Windows 7 32-bit and then it is

necessary to support Windows 7 64-bit, then the driver must be recertified. The Microsoft certification process must

be initiated again, and the reseller fee must be paid to Microsoft for the 64-bit version of the driver. Microsoft

requires this certification process which involves Windows hardware quality labs testing (WHQL). It certifies that

the hardware or software has been tested by Microsoft to ensure compatibility. Device drivers that pass the WHQL

tests are given a digitally signed certification file, which prevents Windows from displaying a warning message that

the driver has not been certified by Microsoft.

Figure 1 shows the default VID and PID values for the device and drivers. To establish communication with the

driver, the VID and PID of the device must match the driver. Notice that the default CP210x device VID and PID

match the default VCP driver VID and PID numbers.

AN721 Datasheet(PDF) 2 Page - Silicon Laboratories