What is serial communication?

In serial communication, data is sent in the form of binary pulses. In other words, we can say that binary 1 means a logic high or 5 volts, and 0 means a logic low or 0 volts. Serial communication can take various forms, depending on the mode of transmission and the type of data transmission. This transmission mode is classified as simplex, half-duplex and full-duplex. There is one transmitter and receiver for each transmission mode. There is one transmitter and receiver for each transmission mode.

 

Transmission mode - serial communication

Simplex refers to one-way communication technology. There is only one client (the sender or receiver is active at the same time). If the sender sends it, the receiver can only accept it. Television communication is a simplex mode, the television station sends and the television receives.

In half-duplex mode, both the sender and the receiver are active, but not active at the same time, ie if the sender sends, the receiver can accept but not send, and vice versa. The Internet is a good example. If the laptop sends a request for a web page, the web server will process the application and send back the information.

Full-duplex mode is widely used in the world for communication. Both the sender and the receiver can send and receive at the same time. An example is your smart phone.

Data transfer can be done in two ways. They are serial communication and parallel communication. Serial communication is a technique for transmitting data bit by bit using a two-wire, that is, transmitter (transmitter) and receiver

 

The difference between serial and parallel communication

Serial communication only sends one bit at a time. Therefore, these require less I/O (input-output) lines. Hence, it takes up less space and is more resistant to crosstalk. The main advantage of serial communication is that the cost of the entire embedded system becomes cheap and the information can be transmitted over long distances. Serial transmission is used for DCE (data communication equipment) devices such as modems.

In parallel communication, one block of data (8, 16 or 32 bits) is transmitted at a time. Therefore, each data bit requires a separate physical I/O line. The advantage of parallel communication is that it has fast speed but the disadvantage is that it uses more I/O (input-output) lines. Parallel transmission is used for PCs (Personal Computers) for interconnecting CPUs (Central Processing Units), RAM (Random Access Memory), modems, audio, video and network hardware.

Note: If your integrated circuit or processor supports a small number of input/output pins, you’d better choose serial communication.

 

How does serial communication work?

Advanced CPUs such as microcontrollers and microprocessors communicate with the outside world and chip peripherals using serial communication. To be familiar, let us give a simple example. Suppose you want to send a file from your laptop to your smart phone. How would you send it? Maybe use Bluetooth or WiFi protocol, right.

Therefore, the following are the steps to establish serial communication.

Add connection

In the first step, your laptop will search for devices near 100 meters and list the devices found. This process is often called roaming

Select the device to communicate with

To connect to your phone, you must complete the pairing. The default configuration already exists in the software. Therefore there is no need to manually configure the baud rate. In addition, there are four unknown rules. They are the baud rate, data bit selection (framing), start and stop bits and parity.

 

Serial port common protocol

RS232 protocol

RS232 is the first serial protocol for connecting to a telephone modem. RS stands for recommendation standard and it is now changed to EIA (Electronic Industries Alliance) / TIA (Telecommunications Industry Association).

It is also used in modems, mice and CNC (computing digital computing) machines. You can only connect a single transmitter to a single receiver.

It supports full-duplex communication and allows baud rates up to 1Mbps.

The cable length is limited to 50 feet.

As you know, the data stored in memory is in bytes. You may wonder how byte data is converted to binary bits? The answer is the serial port.

The serial port has an internal chip called UART. UART is an acronym for the Universal Asynchronous Receiver Transmitter, which converts parallel data (bytes) into a bitwise serial form.

The RS232 serial port has nine pins, which are divided into male and female heads. The RS 232C serial communication interface is a successor to RS232.

All of the features in RS232 are stored in the RS232C model, but it has 25 pins. Of the 25 or 9 pins, we only use three pins to connect to the terminal device.

 

RS422 interface

We can only transfer data up to 1Mpbs using RS232. In order to solve this problem, RS422 occurs. RS422 is a multipoint serial interface. We can connect 10 transmitters to 10 receivers at a time using a single bus. It uses two twisted pair cables (differential configuration) to send data. The cable has a length of 4000 feet and a baud rate of 10 Mbps.

 

RS485 interface

RS485 is the industry's preferred protocol. Different from RS422, you can connect 32 line drivers and 32 receivers in a differential configuration. The transmitter is also known as a line driver. However, only one transmitter is active at a time.

 

Conclusion

Serial communication is an important part of the field of electronic devices and embedded systems. If two devices are needed to exchange information on the same bus, the data transfer rate is critical. Therefore, it is necessary to choose a valid serial protocol for any application.