A collection of guidelines called a communication protocol enables data transmission between two or more communication systems over any physical media. The term “protocol” refers to the rules, guidelines, synchronization between communication systems, required syntax, and semantics. A combination of hardware and software can be used to implement protocols. Different communication protocols are commonly used in analogue and digital communication systems. Each protocol also has a specific set of applications.
Protocols for Communication in Embedded Systems
An electronic system or device that uses both hardware and software is called an embedded system. A processor or controller receives input from devices that are part of the physical environment, such as sensors, actuators, etc., processes that information using the right software, and then produces the intended result.
In this instance, for the components to deliver the desired output, they must communicate with one another. To communicate information, each communication entity should consent to a protocol. Embedded systems can use a wide variety of protocols, which are implemented according to the application domain. In general, the physical layer of a communication protocol describes the signals that are included, their strength, how they are shaken, how buses are arbitrated, how devices are addressed, whether they are wired or wireless, and so on.
The application layer is involved in operations like system configuration, baud rate choice, and data transmission and reception.
Embedded Systems’ Communication Protocol Types
Two general categories can be used to classify communication protocols:
- Inter System Protocol
- Intra System Protocol
Protocols for Inter-System Communication
Communication between two communicating devices, such as a PC and a microprocessor kit, development boards, etc., is established using inter system protocols. In this instance, the inter bus system is used to facilitate communication.
Inter System Communication Protocols: Types
The following inter system protocols can be categorized:
- USB Communication protocols
- UART Communication protocols
- USART Communication protocols
Protocols for USB Communications
The USB protocol is a two-wire serial communication standard. It permits 127 devices to connect simultaneously. Plug & play functionality is supported by USB.
Through data signal lines D+ and D-, the USB protocol transmits and receives data serially between the host and external peripheral devices. In addition to two data lines, USB powers a device using VCC and Ground signals. Figure 4 below shows the USB pin out.
When two devices connect with one another, data is sent as packets. Eight bits (or bytes) make up a data packet, with the LSB (The Least Significant Bit) transmitted first.
When transmitting data, USB uses the NRZI (Non Return to Zero Invert) encoding scheme in conjunction with the sync field to synchronize the clock signals of the host system and the receiver.
Protocols for UART Communications
The Universal Asynchronous Receiver/Transmitter (UART) is merely a piece of hardware that transforms parallel data into serial data; it is not a communication protocol. Its primary function is serial data transmission and reception.
Protocols for intra system communication
The circuit board’s components can communicate with one another thanks to the intra system protocol. Intra system protocol expands the number of devices linked to the controller in embedded systems.
Circuit complexity and power consumption increase as component count rises. Data from the peripherals will be accessed securely, according to intra system protocol.
Intra System Communication Protocols: Types
The types of intra system protocol include:
- I2C Protocol
- SPI Protocol
- CAN Protocol
Protocols for I2C Communications
Philips Semiconductors created the Inter Integrated Circuit (I2C) serial communication standard. This protocol’s primary goal is to make it simple to connect peripheral chips to microcontrollers. In embedded systems, the microcontroller is connected to all peripheral devices as memory mapped devices.
A master to slave communication protocol is the I2C protocol. Each slave is given a distinct address. The target slave address and R/W (Read/Write) flag are originally sent by the master device in order to initiate communication. Other devices will remain in the off state while the matching slave device switches to the active mode.
Communication between the master and slave devices begins as soon as the slave device is prepared. If the transmitter transmits 1 byte (8 bits) of data, the receiver responds with a single bit of acknowledgment. At the conclusion of device-to-device communication, a stop condition is issued.
Protocols for Serial Peripheral Interface (SPI)
One of the serial communication protocols invented by Motorola is SPI (Serial Peripheral Interface). MOSI (Master Out Slave In), MISO (Master In Slave Out), SS (Slave Select), and SCLK make up the 4-wire protocol (Serial Clock).
SPI is a master-slave communication protocol, similar to the I2C protocol. In SPI, the master device sets the clock at a specific frequency initially. Additionally, the SS line, which is typically held high, is pulled low to choose the proper slave.
As soon as the proper slave device is chosen, communication between the chosen slave and master device is established.
Full-duplex communication is a feature of SPI. Data transport is not constrained to 8 bit words by SPI.
Protocol for Controller Area Network (CAN) communication
Robert Bosch created the serial communication system known as CAN (Controller Area Network) for use within vehicles. For data transfer, CAN High (H+) and CAN Low (H-) lines are required.
Message-oriented communication protocol is the foundation of the CAN system.
Sometimes companies are releasing their own security protocols for the products they are producing. For example — Ajax Systems, security systems manufacturer, who developed two communication protocols for wired and wireless devices for maximum protection level. Both protocols are working over a great distance of 2000 metres and are encrypted.