Not enough USB ports? Teach you single-channel USB to multi-channel serial port solution

The serial port should be familiar to friends in the electronics industry. It is a very common protocol for device communication. 

Most desktop chassis have RS232-DB9 interfaces and multiple USB interfaces.

Laptops usually only have 3 USB ports and no DB9 port. If you want to use the serial port function, you can only use a USB-TTL module.

If multiple serial ports are required, multiple USB ports will be occupied, and the USB ports provided by the PC will not be sufficient if a mouse, a debugger, etc. are added.

This article shares several solutions using a single USB port to multiple serial ports. The serial ports are independent of each other and do not interfere with each other.

1. CH9342 single chip realizes dual serial ports

If you only need two serial ports at most, then CH9342 is a good choice. It is a single-channel USB-to-dual serial port chip, which provides two full-duplex 9-wire asynchronous serial ports UART0/1, which are used to expand asynchronous serial ports for computers. , or upgrade common serial device to USB bus.

2. CH9344 single chip realizes 4 serial ports

If the two serial ports are not enough, don't worry, we still have 4 serial port chips. CH9344 is a single-channel USB to 4 serial port control chip, which provides 4 sets of full-duplex asynchronous serial ports UART0/1/2/3 for Extend asynchronous serial port for computer, or upgrade common serial port device to USB bus

Only a 30M crystal and a small amount of capacitors are needed externally, it supports baud rate 1200-7.8125Mbps, and is packaged in LQFP-48.

3. CH934X+CH438 realize multiple serial ports

If you need more serial ports, you can try the combination of CH934X and CH438.

CH943X is a USB to multi-serial port control chip, which is mainly responsible for processing all data transmission of USB interface, and operates CH438 through parallel interface to realize the receiving and sending of multiple serial port data.

After installing the driver, insert the USB to serial port module, and there will be multiple serial ports on the computer. The operation mode of these serial ports is exactly the same as the serial ports that come with the computer. Each serial port is independent of each other and does not interfere with each other.

4. GL850G + serial port chip realizes multiple serial ports

With a 4-channel serial port chip, what if you want a 6-channel, 8-channel, 12-channel, and 16-channel serial port chip?

Very simple, just need to add a USB Hub chip.

GL850G is a USB 2.0 HUB chip. Many USB extenders on the market are based on this chip. It can expand one USB port to four USB ports at most.

In order to support the serial port function, we need to add a USB-TTL chip to each extended USB port, and there are more choices of serial port chips. The single serial port includes domestic CH340/CH341 series, foreign FT232, PL2303, CP2102 Wait, the prices of these serial chips are quite different, and the maximum supported baud rates are also different, so choose according to your needs.

There are multiple serial ports, CH9342 with 2 serial ports, and CH9344 with 4 serial ports.

If you want to implement multiple serial ports, you can refer to the following combination scheme:

6 serial ports: GL850G + 3 CH9342

6 serial ports: GL850G + 1 CH9342 + 1 CH9344

8 serial ports: GL850G + 2 CH9344

Here is an application scheme based on GL850G two-way serial port expansion + 1-way USB.

GL850G supports up to 4 USB channels, I only use 3 of them, 2 of them are serial ports, and the other 1 is female USB, which can be used for cascading two modules, or used to connect debuggers, mouse and keyboard, etc. USB device.

The application mode of GL850G Hub chip + serial port chip is more flexible, which can expand the USB port while expanding the serial port.

The CH9344 application circuit is relatively simple, only a single chip can realize 4 serial ports. The choice of the above solutions should comprehensively consider the chip price, the number of serial ports, the baud rate range, etc. Of course, if it is made by yourself and used for normal debugging, it does not matter.

USB-TTL module

USB to multi-channel serial port solution

CH9342 single chip realizes dual serial ports

CH9344 single chip realizes 4 serial ports

CH934X+CH438 realize multiple serial ports