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What are the UART Communication Protocols

Release date:2022-4-30 0:07:33

What’s UART?

UART is Universal Asynchronous Receiver/Transmitter.

UART is a universal serial data bus mainly used for asynchronous communication. Such a universal serial data bus belongs to bidirectional communication and can realize full-duplex transmission and reception. It converts the data and data to be transmitted between serial communication and parallel communication. As an integrated chip that can convert parallel input signals into serial output signals, UART is usually used for component integration or linking of other communication interfaces. The specific materialization is shown as some independent modules, or as some peripheral curing equipment integrated in the microprocessor. It is generally of RS-232C specification, and is matched with standard signal amplitude conversion chips such as Maxim's MAX232 as an interface for connecting external devices.


What are the pin interfaces used in UART communication?

In UART communication, two UARTs can communicate with each other directly. The sending UART converts parallel data from a control device such as a CPU into serial data, and sends the converted serial data to the receiving UART, which then converts the serial data back to the parallel data of the receiving device. The data flows from the Tx pin of the sending UART to the Rx pin of the receiving UART. The hardware connection is also very simple, only 3 lines need to be connected. If the high and low levels of the UARTs of the two devices are inconsistent, you need to convert the level before proceeding. One step connection.

TX - Data Transmitter Interface (text)

RX - data receiver interface (receive)

GND - It is necessary to ensure that the two devices share the same ground and have a unified reference plane

What are the UART communication protocols?

Serial communication means that the serial port sends and receives bytes according to the number (bit). Although the serial communication rate of bytes is slower, serial ports can use a single wire to send data while using another wire to receive data. Serial communication protocol means that when the content of the data packet has been specified, and the content includes the start bit, main data, check bit and stop bit, the sender and the receiver need to agree on a consistent data packet format to be able to operate normally. Specifications for sending and receiving data. In serial communication, commonly used protocols include: RS-232, RS-422 and RS-485.

Start bit

Data bit

Parity bit

Stop bit

1 bit

5-9 bit

0-1 bit

1-2 bit


Following as UART commonly used protocols:

RS-232(ANSI/EIA-232 standard) is the serial connection standard on IBM-PC and its compatibles. It has a wide range of uses, such as connecting a mouse, a printer or a Modem, and it can also be connected to industrial instruments and meters for driver and connection improvements. In practical applications, the transmission length or speed of RS-232 often exceeds the general standard. standard value. RS-232 is limited to point-to-point communication between the PC serial port and the device (the maximum distance of RS-232 serial port communication is 50 feet).

RS-422(EIA RS-422-AStandard) is the serial connection standard for Apple's Macintosh computers. RS-232 uses unbalanced ground-referenced signals, while RS-422 uses differential signals. Differential signal transmission uses two wires to send and receive signals. Compared with RS-232, it has better noise immunity and longer transmission distance, and in industrial applications, this will be a very big advantage.

RS-485(EIA-485 standard) is an improved version of RS-422, because it increases the number of available devices from 10 to 32, and defines a certain number of devices in the case of the maximum number of devices. Some electrical characteristics to ensure that there can be enough signal voltage output. With the capability of multiple devices, you can also use a single RS-485 port for device networking. RS-485, with its excellent noise immunity and multi-device availability, is the choice for serial data connections in the establishment of distributed device networks connected to PCs, other data collection controllers, HMIs, or other operational industrial applications. RS-485. RS-485 is a superset of RS-422, so virtually all RS-422 devices can be controlled by RS-485. In addition, RS-485 can also use about 4000 feet (ultra-long distance) line for serial data communication.


What is UART wireless serial port module?

The wireless serial port module is a communication device that integrates software and hardware. The wireless serial port module includes MCU and RF radio frequency chips, and has a built-in wireless communication protocol. In short, it is a module that can communicate wirelessly through the serial port, reducing its development cost and the difficulty of development shortens the product development cycle. The user does not need to care about its complicated radio frequency communication process, but only needs to receive and send the data to be processed through the serial port. All of HYXKIOT’s Bluetooth modules communicate through UART, we have developed UART wireless serial port modules based on various radio frequency chips for different fields and different application scenarios (wireless meter reading, smart furniture).

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