What Is SPI Interface? How SPI Works?

What Is SPI Interface? How SPI Works?

SPI stands for Serial Peripheral interface and, as the name suggests, a serial peripheral interface. Motorola was first defined on its MC68HCXX-series processors.  SPI is a high-speed, full-duplex, synchronous communication bus, and only occupy four lines on the chip pin, saving the pin of the chip, while saving space for the PCB layout, providing convenience, mainly used in EEPROM, FLASH, real-time clock, AD converter, and between the digital signal processor and digital signal decoder.

     The SPI has two master and slave modes. An SPI communication system needs to include one (and only one) master device and one or more slave devices. The main device (Master) provides the clock, the slave device (Slave), and the SPI interface, which are all initiated by the main device. When multiple slave devices exist, they are managed by respective chip signals. The SPI is a full-duplex, and the SPI does not define a speed limit, and the general implementation can usually reach or even exceed 10 Mbps.

      The SPI interface generally uses four signal lines for communicating:

SDI (Data Entry), SDO (Data output), SCK (Clock), CS (Select)

MISO: Primary device input/output pin from the device. The pin sends data in the mode and receives data in the main mode.

MOSI: Primary Device Output/input pin from the device. The pin sends data in the main mode and receives data from the mode.

SCLK: Serial clock signal, generated by the main equipment.

CS / SS: Select signal from the equipment, controlled by the main equipment. It functions as a “chip selection pin”, which selects the specified slave device, allowing the master device to communicate with a specific slave device alone and avoid conflicts on the data line.

     In recent years, the combination of SPI (Serial Peripheral Interface) technology and OLED (Organic Light-Emitting Diode) displays has become a focal point in the tech industry. SPI, known for its high efficiency, low power consumption, and simple hardware design, provides stable signal transmission for OLED displays. Meanwhile, OLED screens, with their self-emissive properties, high contrast ratios, wide viewing angles, and ultra-thin designs, are increasingly replacing traditional LCD screens, becoming the preferred display solution for smartphones, wearables, and IoT devices.