24/12/2025
I2C and SPI are two widely used serial communication buses in embedded and electronics systems, each suited for different design needs. I2C uses only two shared lines: SDA for data and SCL for clock. It supports multiple slaves on the same bus using device addresses, with arbitration and open-drain signaling that allows multiple masters if required. This makes I2C ideal for low-speed, short-distance communication with sensors, EEPROMs, RTCs, and configuration ICs where pin count must be minimized. SPI, in contrast, is a driven, device-selected bus that uses separate lines for clock (SCLK), data out from master (MOSI), data into master (MISO), and individual chip-select lines for each slave. This structure allows much higher data rates, full-duplex communication, and simpler protocol timing, at the cost of more pins and wiring. SPI is commonly used for displays, ADCs, DACs, flash memory, and high-speed peripherals. Choosing between I2C and SPI depends on speed, pin availability, number of devices, and system complexity.