关于STM32F103的SPI主机的NSS硬件控制问题

歹徒兄弟提问时间：2019-6-13 20:29 /

问答
是否解决:

#ifdef SPI3_NSS_HARD
#define SPI3_CS_ENABLE          SPI_Cmd(SPI3, ENABLE)
#define SPI3_CS_DISABLE          SPI_Cmd(SPI3, DISABLE)
#else
#define SPI3_CS_ENABLE          PAout(15)=0
#define SPI3_CS_DISABLE          PAout(15)=1
#endif

void SPI3_Configuration(void)
{
SPI_InitTypeDef  SPI_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);

GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE);//JTAG Disable SWDP Enable

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3  |  GPIO_Pin_4  | GPIO_Pin_5;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/* SPI: CS推挽输出 */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
#ifdef SPI3_NSS_HARD
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
#else
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
#endif
  GPIO_Init(GPIOA, &GPIO_InitStructure);

/* SPI 初始化定义 */
  SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex; //SPI设置为双线双向全双工
  SPI_InitStructure.SPI_Mode = SPI_Mode_Master;                   //设置为主 SPI
  SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;                //SPI发送接收 8 位帧结构
  SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;                      //时钟悬空高
  SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;                      //数据捕获于第二个时钟沿
  #ifdef SPI3_NSS_HARD
SPI_InitStructure.SPI_NSS = SPI_NSS_Hard;                         //硬件控制 NSS 信号
  #else
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;                         //软件控制 NSS 信号
#endif
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2; //波特率预分频值为2
  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;                //数据传输从 MSB 位开始
  SPI_InitStructure.SPI_CRCPolynomial = 7;                         //定义了用于 CRC值计算的多项式
  SPI_Init(SPI3, &SPI_InitStructure);
#ifdef SPI3_NSS_HARD
SPI_SSOutputCmd(SPI3, ENABLE);
SPI_Cmd(SPI3, DISABLE);
#else
SPI_Cmd(SPI3, ENABLE);
#endif

DMA_Config();
}

如上定义宏SPI3_NSS_HARD配置为硬件控制NSS输出，现烧录两个硬件：一个是采用HSI+PLL时钟64MHz，另一个采用HSE+PLL时钟72MHz。

测试如下代码：

void SFLASH_FastReadNByte(uint8_t* pBuffer, uint32_t ReadAddr, uint16_t nByte)
{
  while (PAin(15)==0);//Wait CS Disable
SFLASH_WaitForNoBusy();
SPI3_CS_ENABLE;                               //使能器件
  SPI3_WriteByte(SFLASH_FAST_READ);             //《快读数据》指令
  SPI3_WriteByte((uint8_t)((ReadAddr)>>16));    //发送24bit地址
  SPI3_WriteByte((uint8_t)((ReadAddr)>>8));
  SPI3_WriteByte((uint8_t)ReadAddr);
  SPI3_WriteByte(0xFF);                         //等待8个时钟

  while(nByte--)                               //循环读数
  {
*pBuffer = SPI3_ReadByte();
pBuffer++;
  }

  SPI3_CS_DISABLE;                               //失能器件
}

uint8_t SPI3_WriteByte(uint8_t TxData)
{
  while((SPI3->SR & SPI_I2S_FLAG_TXE) == (uint16_t)RESET);
  SPI3->DR = TxData;

  while((SPI3->SR & SPI_I2S_FLAG_RXNE) == (uint16_t)RESET);//发现程序会卡在此处
  return SPI3->DR;
}

发现64MHz硬件运行正常，但72MHz时钟硬件程序会卡在“while((SPI3->SR & SPI_I2S_FLAG_RXNE) == (uint16_t)RESET);”导致异常复位，而如果不采用硬件控制NSS信号输出（即不定义宏SPI3_NSS_HARD）则都不会有此问题。到底是我的代码有bug还是在运行SPI_Cmd(SPI3, ENABLE)使能SPI后到SPI正常工作有延迟。请高人指教。