MCU与FPGA通讯SPI代码

以下是MCU与FPGA之间使用SPI通信的代码示例（以STM32为例）：

#include "stm32f4xx.h"

#define SPIx                          SPI1
#define SPIx_CLK                      RCC_APB2Periph_SPI1
#define SPIx_CLK_INIT                 RCC_APB2PeriphClockCmd

#define SPIx_SCK_PIN                  GPIO_Pin_5
#define SPIx_SCK_GPIO_PORT            GPIOA
#define SPIx_SCK_GPIO_CLK             RCC_AHB1Periph_GPIOA
#define SPIx_SCK_SOURCE               GPIO_PinSource5
#define SPIx_SCK_AF                   GPIO_AF_SPI1

#define SPIx_MISO_PIN                 GPIO_Pin_6
#define SPIx_MISO_GPIO_PORT           GPIOA
#define SPIx_MISO_GPIO_CLK            RCC_AHB1Periph_GPIOA
#define SPIx_MISO_SOURCE              GPIO_PinSource6
#define SPIx_MISO_AF                  GPIO_AF_SPI1

#define SPIx_MOSI_PIN                 GPIO_Pin_7
#define SPIx_MOSI_GPIO_PORT           GPIOA
#define SPIx_MOSI_GPIO_CLK            RCC_AHB1Periph_GPIOA
#define SPIx_MOSI_SOURCE              GPIO_PinSource7
#define SPIx_MOSI_AF                  GPIO_AF_SPI1

#define SPI_CS_PIN                    GPIO_Pin_4
#define SPI_CS_GPIO_PORT              GPIOA
#define SPI_CS_GPIO_CLK               RCC_AHB1Periph_GPIOA

#define SPIx_DMA                       DMA2
#define SPIx_DMA_CLK                   RCC_AHB1Periph_DMA2

uint8_t data_to_send = 0x55;
uint8_t received_data = 0;

void SPI_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
  SPI_InitTypeDef  SPI_InitStructure;

  /* Enable GPIO clocks */
  RCC_AHB1PeriphClockCmd(SPIx_SCK_GPIO_CLK | SPIx_MISO_GPIO_CLK | SPIx_MOSI_GPIO_CLK, ENABLE);

  /* Enable SPI clock */
  SPIx_CLK_INIT(SPIx_CLK, ENABLE);

  /* Configure SPI pins */
  GPIO_InitStructure.GPIO_Pin = SPIx_SCK_PIN | SPIx_MISO_PIN | SPIx_MOSI_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* Connect SPI pins to AF */
  GPIO_PinAFConfig(SPIx_SCK_GPIO_PORT, SPIx_SCK_SOURCE, SPIx_SCK_AF);
  GPIO_PinAFConfig(SPIx_MISO_GPIO_PORT, SPIx_MISO_SOURCE, SPIx_MISO_AF);
  GPIO_PinAFConfig(SPIx_MOSI_GPIO_PORT, SPIx_MOSI_SOURCE, SPIx_MOSI_AF);

  /* Configure SPI */
  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_Low;
  SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
  SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
  SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
  SPI_InitStructure.SPI_CRCPolynomial = 7;
  SPI_Init(SPIx, &SPI_InitStructure);

  /* Enable SPI */
  SPI_Cmd(SPIx, ENABLE);
}

void SPI_CS_Enable(void)
{
  GPIO_ResetBits(SPI_CS_GPIO_PORT, SPI_CS_PIN);
}

void SPI_CS_Disable(void)
{
  GPIO_SetBits(SPI_CS_GPIO_PORT, SPI_CS_PIN);
}

void SPI_SendData(uint8_t data)
{
  while (SPI_I2S_GetFlagStatus(SPIx, SPI_I2S_FLAG_TXE) == RESET);
  SPI_I2S_SendData(SPIx, data);
}

uint8_t SPI_ReceiveData(void)
{
  while (SPI_I2S_GetFlagStatus(SPIx, SPI_I2S_FLAG_RXNE) == RESET);
  return SPI_I2S_ReceiveData(SPIx);
}

void SPI_SendByte(uint8_t byte)
{
  /* Enable CS */
  SPI_CS_Enable();

  /* Send byte */
  SPI_SendData(byte);

  /* Disable CS */
  SPI_CS_Disable();
}

uint8_t SPI_ReceiveByte(void)
{
  uint8_t byte;

  /* Enable CS */
  SPI_CS_Enable();

  /* Receive byte */
  byte = SPI_ReceiveData();

  /* Disable CS */
  SPI_CS_Disable();

  return byte;
}

int main(void)
{
  /* Initialize SPI */
  SPI_Configuration();

  /* Initialize CS pin */
  GPIO_InitTypeDef GPIO_InitStructure;
  RCC_AHB1PeriphClockCmd(SPI_CS_GPIO_CLK, ENABLE);
  GPIO_InitStructure.GPIO_Pin = SPI_CS_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(SPI_CS_GPIO_PORT, &GPIO_InitStructure);

  /* Send and receive data */
  received_data = SPI_ReceiveByte();
  SPI_SendByte(data_to_send);

  while (1)
  {
  }
}

上述代码中，`SPI_Configuration`函数用于初始化SPI，`SPI_CS_Enable`和`SPI_CS_Disable`函数用于使能和禁用从设备的CS信号，`SPI_SendData`和`SPI_ReceiveData`函数用于发送和接收数据，`SPI_SendByte`和`SPI_ReceiveByte`函数用于发送和接收单个字节。