🚗The Great Communication Protocol Battle: Why Do Some Chips Use UART, Others Use SPI, and Some Prefer I2C? The Truth is More Complex Than You Think!🎯

🎓 Keywords: UART, SPI, I2C, chip communication, hardware design🧑🔧 Target Audience: Electronics beginners, communication novices, embedded developers

🚀 Opening Statement: It’s not the chips choosing the protocol, it’s the “application scenario” that dictates the protocol!

You may have encountered this situation while working on a project:

• A certain temperature sensor requires I2C
• A specific external Flash module uses SPI
• Communication with a Bluetooth module is done via UART

Before you know it, all three communication ports on the MCU are in use! You can’t help but ponder:

“What’s going on here? Why can’t we standardize? Wouldn’t it be better to just use SPI?”

The answer is actually quite simple:

These protocols are not competing for attention; they are specialized for different tasks.

🔍 Introducing the Three Brothers: UART, SPI, I2C

Let’s start with a concept checklist 👇 (make sure not to skip this; these are your “calm judgment guidelines” for project selection)

Protocol	Number of Wires	Speed Level	Master-Slave Structure	Supports Multiple Devices	Implementation Difficulty	Common Applications
UART	2 wires	Medium to low speed	Point-to-point	❌	Low	Module communication, log output
SPI	≥4 wires	High speed	Master-slave	✅ (but requires more pins)	Medium	Flash, screens, ADC
I2C	2 wires	Medium speed	Master-slave	✅ (address differentiation)	High	Sensors, small peripherals

🎯 So why do “different chips” use “different protocols”? The core lies in the following three dimensions:

✅1. Cost vs. Pin Count Balancing Act

If you’re designing a super compact board (like a smartwatch), every inch of space is precious, so do you really want to use four SPI lines? That’s too extravagant!

📌 Example:

• Common temperature and humidity sensors (like SHT3x) use I2C because it only requires two wires and can connect multiple devices, saving space and pins.

🎯 My Opinion:

If you have many peripheral devices around your chip and want to save pins, I2C is your representative of “pin economics”!

✅2. Communication Speed Differences — Who is Fast, Who is Slow, and Who Can Handle Heavy Loads?

Simply put,some protocols are as slow as a tortoise, while others can transfer data millions of times at high speed.

📌 Example:

• If you need to communicate with NOR Flash (like W25Q64), where data can reach dozens of MB, you must use SPI because it can easily run at 10MHz or even higher;
• UART typically has a baud rate of 9600 to 115200, which is slow and elegant but not suitable for transferring large files.

🎯 My Opinion:

For “high-speed data transfer,” choose SPI; for “slow chatting,” use UART; for “medium-speed tasks,” rely on I2C.

✅3. The Device Ecosystem Forces You to Choose a Protocol

You want to use a chip, but it only supports a certain protocol, leaving you no choice!

📌 Example:

• Bluetooth modules (like HC-05) 👉 only support UART
• OLED displays (like SSD1306) 👉 either I2C or SPI as options
• Some MEMS gyroscopes 👉 officially recommend using I2C and only provide address mapping

🎯 My Opinion:

Chip manufacturers are reluctant to provide multiple options; you have to use whatever they choose.

🔥 Practical Illustration of Protocol “Division of Labor” in Real Projects

When you create an MCU control system, such as a smart car, wearable device, or home controller:

MCU Main Control
 ├─ SPI Bus —— Connect Flash, Screen
 ├─ I2C Bus —— Connect Temperature Sensor, RTC
 └─ UART —— Connect Bluetooth/Wi-Fi Module

Each line is just right, not wasting resources, and each has its own role. This is the “art of protocol selection”!

💥 Deepening Memory with Analogies: What are the “Personalities” of the Three Protocols?

Protocol	Personality Analogy	Characteristics
UART	Making a phone call	One-to-one, point-to-point, taking turns to speak and listen
SPI	High-speed dedicated line courier	Fast, direct, monopolizes the line, but requires more wires
I2C	Group chat administrator + nickname	One master, multiple slaves, calls out by address, occasionally fights for the floor

🧠 Conclusion: It’s not about which protocol is superior, but rather what the scenario dictates!

Application Scenario	Recommended Protocol	Reason
Sensors/Simple Peripherals	I2C	Multiple devices with fewer pins, suitable for master-slave structures
Large Capacity Storage/High Refresh Rate Screens	SPI	High speed and stability, transmitting large amounts of data without frame loss
Module Communication/Debugging Port	UART	Simple point-to-point, suitable for asynchronous modules and peripheral communication