stm32f4的SPI的单向只接收模式配置

stm32f4的SPI的单向只接收模式配置，

 SPI_InitStructure.SPI_Direction = SPI_Direction_1Line_Rx; //单线接收模式
  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_2Edge;
  SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
  SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2; //  45/2=22.5MHZ
  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
  SPI_InitStructure.SPI_CRCPolynomial = 7;
  SPI_Init(SPI2 &SPI_InitStructure);

是这样配置吗

为什么读取的数据都是0啊​