STM32 SPI usage

1. SPI usage principle

Data transmission is realized by data exchange, the first jump edge realizes data output, and the second jump edge realizes sampling. As shown in the following figure

2. GPIO configuration

 GPIO_InitTypeDef GPIO_InitStructure;

 //Configure SPI2 pins

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO|RCC_APB2Periph_GPIOB, ENABLE);

 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 |GPIO_Pin_14| GPIO_Pin_15;

 GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;

 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //Multiplex push-pull output

 GPIO_Init(GPIOB, &GPIO_InitStructure);

3. SPI configuration

typedef struct

{

  uint16_t SPI_Direction; //Set direction (2-wire full-duplex, 2-wire receive only, 1-wire send, 1-wire receive)

  uint16_t SPI_Mode; //Mode (slave or master)

  uint16_t SPI_DataSize; //width (8 or 16 bits)

  uint16_t SPI_CPOL; //Clock polarity (low or high)

  uint16_t SPI_CPHA; //Clock phase (first or second transition edge)

  uint16_t SPI_NSS; //Chip select mode (hardware or software)

  uint16_t SPI_BaudRatePrescaler; //Baud rate prescaler (from 2 to 256)  

  uint16_t SPI_FirstBit; //The first bit to be sent (lowest bit or highest bit first)        

  uint16_t SPI_CRCPolynomial; //Set crc polynomial (number) such as 7

}SPI_InitTypeDef;

 //SPI2 configuration options

 RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2,ENABLE);

 SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;

 SPI_InitStructure.SPI_Mode = SPI_Mode_Master;

 SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;

 SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;

 SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;

 SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

 SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_16;

 SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

 SPI_InitStructure.SPI_CRCPolynomial = 7;

 SPI_Init(SPI2, &SPI_InitStructure);

 //Enable SPI2

 SPI_Cmd(SPI2, ENABLE); 

4. Exchange data

u8 SPI_Exchange(SPI_TypeDef* SPIx,u8 Byte)

{

 while((SPIx->SR&SPI_I2S_FLAG_TXE)==RESET); //Wait for the send area to be empty  

 SPIx->DR=Byte; //Send a byte  

 while((SPIx->SR&SPI_I2S_FLAG_RXNE)==RESET);//Wait for receiving a byte 

 return SPIx->DR; //Return received data   

}