I2C vs SPI vs UART: A Beginner's Guide to Sensor Interfaces
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Open any sensor's datasheet and you'll see one of three acronyms: I²C, SPI, or UART. They're the three ways a sensor talks to your board. You don't need to master the electrical theory — but knowing the difference makes wiring and debugging far easier.
I²C — two wires, many devices
I²C uses just two shared wires (SDA and SCL) and can connect many devices on the same pair, each with its own address. It's the most common interface for hobby sensors — temperature, pressure, IMUs, OLED displays. Easy to wire, moderate speed. Watch for address clashes if two devices share an address.
SPI — fast, more wires
SPI is faster than I²C but uses more wires (typically four, plus one chip-select per device). Use it when speed matters — SD cards, high-refresh displays, and fast ADCs. The trade-off is extra pins.
UART — simple point-to-point
UART (often just called "serial") is a simple two-wire, device-to-device link (TX and RX). It's how GPS modules, GSM modems, and many breakout boards talk — and how your board talks to your computer. Great for one-to-one, not for many devices on one bus.
Quick comparison
| Interface | Wires | Speed | Best for |
|---|---|---|---|
| I²C | 2 (shared) | Moderate | Most sensors, displays |
| SPI | 4+ | Fast | SD cards, fast displays |
| UART | 2 (point-to-point) | Moderate | GPS, GSM, modules |
The practical takeaway
You rarely choose the interface — the sensor does. What matters is knowing how to wire each, and that 3.3V and 5V boards must match logic levels (use a level shifter when they don't). Most sensor modules handle the details for you on a breakout board.
Browse genuine, board-ready modules in our Sensors and Dev Boards collections. Wiring up something tricky? Ask VoltIQ for the exact connections.