Some of the Arduino Uno or Nano boards use CH340g USB to serial converter chip. If your system does not have the driver installed, it may cause some issues when you connect your Arduino board to the computer. The arduino IDE may not be able to detect the board you connected.
After you connect Arduino board to your PC, go to “Device Manager”, if you see the picture bellow shows “USB2.0-Serial” under “Other devices”, that indicates the CH340g driver has not been installed to your system.
The problem can be solved by installing the CH340g driver. You can download the driver for CH340g from the manufacturer’s official website:
http://www.wch.cn/download/CH341SER_EXE.html
Click “DOWNLOAD”, a file named “CH341SER.EXE” will be downloaded to your computer. Then simply double click the exe file, It should open a dialog box shown below. Click “INSTALL”
The installation will take a few minutes. After installation is done, go to “Device Manager” and check if you can see the “USB-SERIAL CH340 (COM19) under “Ports” (see picture below).
Now the driver for CH340g is installed successfully. You can connect your Arduino board to your PC, the Arduino board should be detected without problem.