Communication Protocols in Embedded Systems

1. What Are Communication Protocols?

A communication protocol is a set of rules that allows two or more electronic devices to talk to each other.

Just like humans need a language to understand each other, electronic devices need protocols. These rules tell them:

• How to send and receive data
• How to know when the message starts and ends
• How to avoid errors

2. Why Are Protocols Needed?

In embedded systems, a microcontroller often communicates with:

• Sensors (like temperature or light sensors)
• Displays (like OLED or LCD screens)
• Memory chips or other microcontrollers

Without communication protocols, devices would just send random signals, and the data would be meaningless.

3. Common Communication Protocols

There are several protocols used in embedded systems. The most common are:

• UART
• I2C
• SPI
• CAN
• USB
• One-Wire

UART (Universal Asynchronous Receiver/Transmitter)

UART is a simple way for two devices to communicate using two wires:

• TX – Transmit data
• RX – Receive data

It is called “asynchronous” because it does not use a clock wire. Both devices must agree on a speed (baud rate). Example: Arduino Serial Monitor or GPS modules.

I2C (Inter-Integrated Circuit)

I2C uses two wires:

• SDA – Data line
• SCL – Clock line

- It is “synchronous” because it uses a clock line to coordinate data. - Multiple devices can share the same two wires. - Each device has a unique address so the microcontroller knows who to talk to. Example: OLED displays, temperature sensors.

SPI (Serial Peripheral Interface)

SPI uses four wires (or more if multiple devices):

• MOSI – Master Out, Slave In
• MISO – Master In, Slave Out
• SCK – Clock
• CS – Chip Select (one per device)

- Fast communication, full-duplex (send and receive at the same time). - Each device requires its own CS pin. Example: SD cards, TFT displays.

CAN (Controller Area Network)

CAN is used in cars and industrial systems. It is reliable and works well in noisy environments. It uses two wires: CAN High and CAN Low. Multiple controllers can communicate safely.

USB (Universal Serial Bus)

USB is a standard high-speed protocol used to connect computers to devices. It uses four wires: Data+, Data-, VCC, and GND. Example: Microcontroller programming, keyboards, flash drives.

One-Wire

One-Wire communication uses only one data wire plus ground. Each device has a unique ID. Example: DS18B20 temperature sensors.

4. Quick Comparison

5. Summary

Communication protocols are like “languages” for electronic devices. Each protocol has its own rules, advantages, and limitations. - UART → simple two-device communication - I2C → few wires, multiple devices - SPI → fast, more wires - CAN → industrial reliability - USB → high-speed standard - One-Wire → minimal wiring