SPI DR寄存器写值，但是发送缓冲区一直非空

只看该作者 · 2018-10-4 10:19

最近想读一下mpu6500的值，但spi一直无法向其发送数据，今天看了看寄存器，发现SR寄存器的发送缓冲区为0，即非空，这说明数据卡在了这，但是不应该是硬件自动从发送缓冲区到移位寄存器然后发送的吗，求助。。。

/* SPI5 init function */
void MX_SPI5_Init(void)
{
/* Peripheral clock enable */
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_GPIOF);
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_SPI5);

  LL_GPIO_InitTypeDef GPIO_InitStruct;
  LL_SPI_InitTypeDef SPI_InitStruct;

  /**SPI5 GPIO Configuration
  PF6 ------> SPI5_CS
  PF7 ------> SPI5_SCK
  PF9 ------> SPI5_MOSI
  PF8 ------> SPI5_MISO
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_7 | LL_GPIO_PIN_9 | LL_GPIO_PIN_8;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_5;
  LL_GPIO_Init(GPIOF, &GPIO_InitStruct);

  SPI_InitStruct.TransferDirection = LL_SPI_FULL_DUPLEX;
  SPI_InitStruct.Mode = LL_SPI_MODE_MASTER;
  SPI_InitStruct.DataWidth = LL_SPI_DATAWIDTH_8BIT;
  SPI_InitStruct.ClockPolarity = LL_SPI_POLARITY_LOW;
  SPI_InitStruct.ClockPhase = LL_SPI_PHASE_1EDGE;
  SPI_InitStruct.NSS = LL_SPI_NSS_SOFT;
  SPI_InitStruct.BaudRate = LL_SPI_BAUDRATEPRESCALER_DIV128;
  SPI_InitStruct.BitOrder = LL_SPI_MSB_FIRST;
  SPI_InitStruct.CRCCalculation = LL_SPI_CRCCALCULATION_DISABLE;
  SPI_InitStruct.CRCPoly = 10;
  LL_SPI_Init(SPI5, &SPI_InitStruct);

  LL_SPI_SetStandard(SPI5, LL_SPI_PROTOCOL_MOTOROLA);

}

//Read a register from MPU6500
uint8_t MPU6500_Read_Reg(uint8_t const reg)
{
  static uint8_t MPU_Rx, MPU_Tx;

  MPU6500_NSS_Low();

  MPU_Tx = reg | 0x80;    //首字节第一位为读写位， 0为写， 1为读
                           //MPU每次读写操作传送两个字节，第一个字节是寄存器地址，第二个是数据
// LL_SPI_TransmitData8(SPI5, MPU_Tx);
  SPI5->DR = MPU_Tx;
  delay_ms(1);
//  MPU_Rx = LL_SPI_ReceiveData8(SPI5);
  while((SPI5->SR & 0x01)==0x01)       //判断接收区是否为空，即判断是否接收到数据
  {
MPU_Rx = SPI5->DR;
  }
  delay_ms(1);
  MPU6500_NSS_High();
  return MPU_Rx;
}