CP2109 USB to UART

The CP2109 USB to UART is the Silicon Labs CP2109 USB to UART Bridge and its VCP driver. You can see how to install this driver as well as see how the USB to UART is installed. This is the CP2109 USB to UART from Silicon Labs but there is also the CP2102 USB to UART on this website. You will note that these are different. There is also the more popular FT232R USB UART driver as you can see.

CP2109 USB to UART

The CP2109 USD to UART has come a long way since it was first released many years back. The most common driver today still being used is the 2014 version of the driver. There have been many changes to this driver since then. They have since dropped Windows XP support and there are still millions of Windows XP machine around.

This was one of the most icon operating systems released by Microsoft. Below you will find the 2021 driver which is the latest drivers, but also the older driver from 2014 which offered Windows XP support. Most of the drivers on this website tend to be XP compatible as their are still users around for this even though support has stopped.

See also  FT234XD USB to Basic UART Driver

Software Versions

The older driver is the Version 6.7 driver for the CP2109 USB to UART which was released in 2014. There was the addition of Windows 8.1 for the driver as well as added support for CP2108 devices. This was also a 64bit as well as a 32bit driver. These are for the Windows 8/8.1 (64/32), 7 (64/32), Vista (64/32), and XP OS versions from Microsoft. The newer driver is the universal driver which is only Windows 10/11 compatible.

  • CP210x USB to UART Bridge Driver (v6.7 – April 11, 2013)

Hardware – CP210x

OS – Windows 2000, Win XP, Win Vista (32/64), Win XP 64 bit, Win 7 (32/64), Win 8 (32/64)

CP210x USB to UART Bridge Driver

  • CP210x USB to UART Bridge Driver (v6.7.6 – June 5, 2018)

Hardware – CP2102N, CP2102, CP2103, CP2104, CP2105, CP2108, CP2109.

OS – Windows 7 (x86 32/64 bit), 8 (x86 32/64 bit), 8.1 (x86 32/64 bit)

CP210x USB to UART Bridge Driver

  • CP210x USB to UART Bridge Driver (v11 – November 5, 2021)

Hardware – CP2102N, CP2102, CP2103, CP2104, CP2105, CP2108, CP2109

OS – Windows 10 (x64, x86), Windows 11 (x64)

 CP210x USB to UART Bridge Driver

Below is some basic usage of the COM port with this USB to UART hardware.

How to Setup a COM Port on the CP2109

Lets first explain some of the syntax which is used to test the COM port on the UART hardware.


HANDLE hMasterCOM = CreateFile(“\\\\.\\COM3”,


You will note that in the CreateFile() function there is a string which contains the COM port which is going to be used. In this example the COM port is 4. The string for this exercise will always start with you selecting the COM port which you are going to use. This is normally COM port 3 which is the most common. We have used port 4 as the example. You can choose which port you will be using for the CP2109 USB to UART device.

See also  UART Drivers Update

(“\\\\.\\COM3”, (Choose your COM port number to use where the UART is attached)

Now the second line contains flags which will be describing the access which in this example is

GENERIC_READ | GENERIC_WRITE, (Generic read and Generic write)

This will allow for read and write access when testing the UART attached. The following parameters being line 3 and 4 will remain 0 and the following line will have to be


This is important when using the CreateFile() for COM applications. The following line should also always be added being the FILE_ATTRIBUTE_NORMAL flag which mainly as it is used primarily for asynchronous transfers. While the FILE_FLAG_OVERLAPPED is optional to use as it tells read and write to the COM port which must specify an OVERLAPPED structure.


The last parameter here  must always be


Now if this function returns successfully, then a handle to the COM port will be assigned to the HANDLE variable. If the function fails, then INVALID_HANDLE_VALUE will be returned. Upon return, check the handle and if it is valid, then you should prepare the COM port that you assigned for data transmission.


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