Summary
I2C is best for applications where you need to connect multiple sensors and devices to a single microcontroller with minimal wiring, while Serial (UART) communication is ideal for simple, long-distance, or point-to-point connections. Both protocols are essential tools in the realm of microcontroller and sensor communication, each serving distinct purposes and providing different advantages depending on the application.
I2C (Inter-Integrated Circuit)
Simply Put:
I2C is a way for small computers and sensors to talk to each other using just two wires. It’s like a classroom where the teacher (master) can talk to many students (slaves) one at a time, and sometimes, there can be more than one teacher. Everyone takes turns talking and listening, making sure no one talks over each other. This makes it easy for them to share information without getting mixed up.
Analogy with reference to the wires / protocol used:
(I2C uses two wires: SDA for data and SCL for clock to connect many devices)
Imagine a classroom where one teacher (master) can talk to many students (slaves). The teacher has two magic strings (SDA for data, SCL for clock) that connect to all students. The teacher can call on any student by name (address) to speak or listen. Sometimes, there can be more than one teacher, but only one teacher talks at a time. This setup allows many devices to talk to each other using just two wires.
Technically Put:
- I2C is a synchronous, multi-master, multi-slave, packet-switched, single-ended, serial communication bus.
- Widely used for communication between microcontrollers and peripheral devices like sensors, displays, and EEPROMs.
Key Features:
- Two-wire Interface: I2C uses two lines, SDA (Serial Data) and SCL (Serial Clock), for communication.
- Addressing: Each device on the bus has a unique address. The master device initiates communication and addresses the slave devices.
- Speed: Standard mode (100 kbps), Fast mode (400 kbps), Fast mode plus (1 Mbps), and High-speed mode (3.4 Mbps).
- Data Transfer: Data is transferred in 8-bit packets followed by an acknowledgment bit.
- Multi-master: Multiple master devices can be connected to the same bus, though only one master can control the bus at any given time.
Roles in Microcontrollers and Sensor Programming:
- Microcontrollers: Often act as the master device, initiating communication and sending/receiving data to/from slave devices.
- Sensors: Act as slave devices, responding to requests from the master and providing data such as temperature, pressure, or acceleration.
Advantages:
- Simple wiring (only two lines needed).
- Supports multiple devices on the same bus.
- Well-suited for short-distance communication within a circuit board.
Disadvantages:
- Limited to relatively short distances (a few meters).
- Data rate is lower compared to other protocols like SPI.
Serial Communication (UART)
Simply Put:
UART is a way for small computers and devices to talk to each other using two wires. It’s like sending letters back and forth. Each letter (or message) can be sent whenever it’s ready, and the devices don’t need to check the clock to know when to send or receive the messages. They just need to agree on how fast they’re sending the letters, so they don’t get mixed up.
Analogy with reference to the wires / protocol used:
(UART uses two wires: TX for sending, RX for receiving)
Imagine two friends with walkie-talkies. Each has a send button (TX) and a receive button (RX). They talk to each other by pressing the send button and listening with the receive button. They agree on how fast to talk so they understand each other. It’s just between the two friends, so only two devices can talk to each other at a time.
Technically Put:
- UART (Universal Asynchronous Receiver/Transmitter) is a hardware communication protocol that uses asynchronous serial communication.
- Commonly used for communication between computers and peripherals or between microcontrollers and modules like GPS, Bluetooth, and serial sensors.
Key Features:
- Asynchronous Communication: No clock signal is used; both devices must agree on the baud rate (bits per second) to ensure correct data transfer.
- Full-duplex Communication: Separate lines for transmission (TX) and reception (RX) allow simultaneous two-way communication.
- Data Frame: Data is sent in packets that typically include a start bit, data bits (5 to 9), an optional parity bit for error checking, and one or more stop bits.
- Baud Rate: Common baud rates include 9600, 19200, 38400, 57600, 115200, and higher.
Roles in Microcontrollers and Sensor Programming:
- Microcontrollers: Can be programmed to send and receive data via UART, making it easy to communicate with PCs, other microcontrollers, or various modules.
- Sensors and Modules: Many sensors and modules use UART for configuration and data transfer, providing an easy interface for reading sensor data or controlling modules.
Advantages:
- Simple and widely supported.
- Suitable for long-distance communication compared to I2C.
- No need for a clock signal.
Disadvantages:
- Requires more wiring (at least two lines for TX and RX).
- Limited to point-to-point communication; not as flexible for connecting multiple devices as I2C.
Key Pointers:
- UART is like a walkie-talkie, where only two devices can talk directly to each other.
- I2C is like a classroom where one teacher can talk to many students using two wires.
- UART uses two wires (TX for sending, RX for receiving).
- I2C uses two wires (SDA for data, SCL for clock) to connect many devices.
- UART devices talk whenever they want, like friends with walkie-talkies.
- I2C devices take turns talking, with the teacher controlling who speaks, like in a classroom.
In microcontroller programming, we use UART when we need simple, direct communication between two devices. We use I2C when we need to connect and communicate with multiple devices using just two wires.
