A USB adapter is a type of protocol converter that is used for converting USB data signals to and from other communications standards. Commonly, USB adapters are used to convert USB data to standard serial port data and vice versa. Most commonly the USB data signals are converted to either RS232, RS485, RS422, or TTL-level UART serial data. The older serial RS423 protocol is rarely used any more, so USB to RS423 adapters are less common.

Uses

USB to serial RS232 adapters are often used with consumer, commercial and industrial applications and USB to serial RS485/RS422 adapters are usually mainly used only with industrial applications. Currently, USB to TTL-level UART converters are used extensively by students and hobbyist as they can be directly interfaced to microcontrollers.

Adapters for converting USB to other standard or proprietary protocols also exist; however, these are usually not referred to as a serial adapter.

The primary application scenario is to enable USB-based computers to access and communicate with serial devices featuring D-Sub (usually DB9 or DB25) connectors or screw terminals, where security of the data transmission is not generally an issue.

USB serial adapters can be isolated or non-isolated. The isolated version has opto-couplers and/or surge suppressors to prevent static electricity or other high-voltage surges to enter the data lines thereby preventing data loss and damage to the adapter and connected serial device. The non-isolated version has no protection against static electricity or voltage surges, which is why this version is usually recommended for only non-critical applications and at short communication ranges.

CH340 Windows Driver Download and Installation Guide

CH340 IC is a low cost USB to TTL converter IC. CH340g IC is used in low cost SMD Arduino UNO & Arduino Nano boards. Many USB to Serial converter IC’s are available in the market but this is a low cost IC that is gaining popularity. USB to TTL converter modules are also available based on this IC. Even Node MCU IOT modules also have this IC.

Step By Step Installation of CH340g Drivers

Initially connect your hardware having CH340 USB to Serial IC to your PC. In the device manager it will show “USB2.0-Serial” (as shown in below figure) which means your ch340 driver has not been installed.

Now extract the CH340g drivers in a folder and in that you will find folder named “CH341SER” in which there will be a “setup” application file as shown below.

Open the setup file and a “Driver Setup” option will open. Just click on the install file.

This installation takes some time. In my laptop it took 1 minute so just have patience. Once installed it will show driver successfully installed. Now go again back to device manager and there you will see that the driver has been successfully been installed and a com port has been allotted. In below image you can see that “com19” has been allotted for ch340g IC in my laptop

Drivers for the ch340 IC has now been installed successfully. I have tested this drivers and installation process in Windows XP, windows 7. Will test is soon on Windows 8 & windows 10.

You can see in above image that Port Number 19 has been allocated to this IC. If you want you can even change the virtual com port number from Device Manager.

History

Historically, most personal computers had a built-in D-sub serial RS232 port, also referred to as a COM port, which could be used for connecting the computer to most types of serial RS232 devices. By the late '90s, many computer manufacturers started to phase out the serial COM port in favor of the USB port. By the mid-2000s, some computers had both a serial COM port and a USB port; however, many no longer had a serial COM port by that time, and today most modern computers have no serial COM port but instead only USB ports.

Since many serial devices with a RS232, RS485 or RS422 port are still in use and even still produced today, the disappearance of the serial COM port from personal computers has created a need for the USB to serial adapter.

Architecture[edit]

Die of a PL2303HX USB to Serial Bridge Controller manufactured by Prolific Technology.

As a simplified example a typical standard USB to serial adapter consists of a USB processor chip which processes the USB signals. The USB processor sends the processed USB signals to a serial driver chip which applies the correct voltages and sends the processed data signals to the serial output.

For the computer to be able to detect and process the data signals drivers must be installed on the computer. Some chip models have drivers installed by default, including FTDI, while drivers for other chip models must be manually installed (e.g. for Windows and MacOS, WCH CH340,[2] Silicon Labs 210x,[3] Prolific PL2303).

When the USB to serial adapter is connected to the computer via the USB port the driver on the computer creates a virtual COM port which shows up in Device Manager on Windows, and under /dev on Linux and MacOS. This virtual COM port can be accessed and used as if it was a built-in serial COM port. However, the characteristics of the virtual COM port are not exactly the same as a real internal COM port, mainly due to data latency; which means that if very sensitive and precise data transfer is required, the USB to serial adapter might be unreliable and not a desired solution. Virtual COM drivers are usually available for Windows