Serial Peripheral Interface
lastmod 2026-08-06created 2026-08-063 edits
Serial Peripheral Interface (Serial Peripheral Interface, SPI) is a de facto standard (with many variants) for synchronous serial communication, used mainly in embedded systems for short-distance wired communication between integrated circuits.
SPI follows a master/slave architecture, in which a device called the master (also called leader, controller, main, etc.) drives the clock and chip select signals to coordinate communication with one or more slave (also called follower, target, sub, etc.) devices. Because there is no formal standard, some manufacturers release devices that can switch roles during operation.
Motorola's original specification (early 1980s) uses four logic signals (also called lines or wires) to support full-duplex communication. It is sometimes called a four-wire serial bus, in contrast to the half-duplex three-wire variant and the two-wire I²C and 1-Wire serial buses.
Typical applications include interfacing microcontrollers with peripheral chips such as SD cards, liquid crystal displays, analog-to-digital and digital-to-analog converters, flash and EEPROM memory, and various communication chips.
Although SPI is a synchronous serial interface, it is different from the Synchronous Serial Interface (SSI). SSI uses differential signaling and provides only a single simplex communication channel.
See also
- Serial communication (Serial Communication)
- Bluetooth Low Energy (BLE)
- Universal asynchronous receiver-transmitter (UART)