Embedded Linux development practice (14): SPI interface development

# Preface

SPI ( Serial Peripheral Interface ), like UART, I2C, CAN, etc., is an important interface for MCU/SOC. Yes, it is a communication interface, a serial communication interface. We think of four-wire interfaces (CS, CLK, MOSI, MISO)

You can choose which SPI device to communicate with through the CS (ChipSelect) or SS (Slave Select) line. The choice is to pull this line low for a period of time.

 Then do the sending and receiving according to the SPI protocol timing:

 SPI mode definition：