Serial Peripheral Interface

Typical SPI bus: master and three independent slaves

The Serial Peripheral Interface (SPI) is a synchronous serial communication interface specification. It is used for short-distance communication, primarily in embedded systems. SPI devices communicate in full duplex mode using a master-slave architecture.

The master (controller) device originates the frame for reading and writing. The SPI may be accurately described as a synchronous serial interface. But it is different from the Synchronous Serial Interface (SSI) protocol.

Developer

The interface was developed by Motorola in the mid-1980s. Later it has become a de facto standard.

Pros and cons

Advantages

• Full duplex communication in the default version of this protocol
• Push-pull drivers (as opposed to open drain) provide good signal integrity and high speed
• Higher throughput than I²C or SMBus. Not limited to any maximum clock speed, enabling potentially high speed
• Complete protocol flexibility for the bits transferred
  • Not limited to 8-bit words
  • Arbitrary choice of message size, content, and purpose
• Simple software implementation

Disadvantages

• Requires more pins on IC packages than I²C, even in the three-wire variant
• No in-band addressing; out-of-band chip select signals are required on shared buses
• SPI does not support hot swapping (dynamically adding nodes)
• Some variants like dual SPI, quad SPI, and three-wire serial buses defined below are half-duplex.

Applications

SPI Serial Memory by Atmel

• Memory: SD Card , MMC , EEPROM , Flash.
• Sensors: Temperature and Pressure.
• Control Devices: ADC , DAC , digital POTS and Audio Codec.
• Others: Camera Lens Mount, touchscreen, LCD, RTC, video game controller, etc.

Other websites

• Intel eSPI (Enhanced Serial Peripheral Interface)
• SPI Tutorial