USB to Serial Cable
1. What is a USB to serial cable?
USB to serial port is to realize the conversion between the computer USB interface and the general serial port. Provides a fast channel for computers without serial ports, and using USB-to-serial devices is equivalent to turning traditional serial devices into plug-and-play USB devices.
So what is a serial port? The full name of the serial port is the serial communication interface. It is a commonly used communication interface for computers. It is characterized by a trapezoidal interface with 9 pins. Generally, desktop computers and industrial computer hosts are equipped with at least one serial port on the back, but most notebooks and some commercial office computers are not equipped with a serial port. In this case, our USB to serial port cable is used to add a serial port to the computer.
2. What is the use of the serial port?
The serial port is used for communication. In the past, it could be connected to external devices such as modems, printers, game consoles, etc. Now, these devices have become USB ports, so the serial port is no longer visible on today's computers. Only on the industrial computer, the serial port is still reserved. Because the serial port has many applications in industrial control.
3. Two concepts you need to know
(1) TTL level: generally used as the level of digital chips. For example, the power supply voltage of the chip is 5V, then the high level is 5V, and the low level is 0V. The level mentioned here is the TTL level.
(2) 232 level: 232 level is the level of a special computer serial port, about -12V is a positive level, and about +12V is a low level. The "USB to serial cable" we just saw and the computer's native serial port are 232 levels.
4. How does the serial port of the microcontroller communicate with the serial port of the computer (or USB-to-serial line)?
Since the serial port of the single-chip microcomputer is TTL level, to communicate with the computer serial port (or USB-to-serial line), it is necessary to make the level logic of the two devices the same to communicate. At this time, you need to use TTL to 232 level chips, commonly used are MAX232, MAX3232, SP232, SP3232 and so on.
The connection method is: MCU serial port—232 chip—serial port
The 232 chip is used for the 5V single-chip microcomputer, and the 3232 is used for the 3.3V single-chip computer. This is the direct reason why the program cannot be downloaded when the 232 chip is added to the 3.3V single-chip computer.
5. What is a USB to TTL chip?
In item 4, if the serial port that is not native to the computer is used, but the serial port converted from USB, the actual hardware connection is: MCU serial port—232 chip—USB to 232 chip—USB port
Then, the USB to TTL chip is born to solve the above redundancy. Using the USB to TTL chip, the connection between the microcontroller and the computer is: microcontroller serial port—USB to TTL chip—USB port
That is, the serial port converted from USB is directly converted into a TTL level that can communicate directly with the microcontroller.
There are many USB to TTL chips, such as: CH340, PL2303, CP2102, FT232, etc.
Welcome to contact us for more USB serial cables: https://www.pcm-cable.com/serial-cable/
