ADIS164888使用SPI读取数据时好时坏

void SPI_FLASH_Init(void){  SPI_InitTypeDef  SPI_InitStructure;  GPIO_InitTypeDef GPIO_InitStructure;  /* Enable SPI1 and GPIO clocks */  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);  /*!< SPI_FLASH_SPI Periph clock enable */  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);  /*!< Configure SPI_FLASH_SPI pins: SCK MISO MOSI*/  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 |GPIO_Pin_7;  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  GPIO_Init(GPIOA, &GPIO_InitStructure);  /*!< Configure SPI_FLASH_SPI_CS_PIN pin: SPI_FLASH Card CS pin */  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;  GPIO_Init(GPIOA, &GPIO_InitStructure);  /* Deselect the FLASH: Chip Select high */  SPI_FLASH_CS_HIGH();  /* SPI1 configuration */  // W25X16: data input on the DIO pin is sampled on the rising edge of the CLK.  // Data on the DO and DIO pins are clocked out on the falling edge of CLK.  SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;  SPI_InitStructure.SPI_Mode = SPI_Mode_Master;  SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;  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_8;  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;  SPI_InitStructure.SPI_CRCPolynomial = 7;  SPI_Init(SPI1, &SPI_InitStructure);  /* Enable SPI1  */  SPI_Cmd(SPI1, ENABLE);}

uint16_t SPI_FLASH_ReadDeviceID(void){  u16 Temp = 0;  /* Select the FLASH: Chip Select low */  SPI_FLASH_CS_LOW();  /* Send "PROD_ID " instruction */  SPI_FLASH_SendTwoByte(0X7E00);  /* Read two bytes from the FLASH */  Temp = SPI_FLASH_SendTwoByte(0xFFFF);  /* Deselect the FLASH: Chip Select high */  SPI_FLASH_CS_HIGH();  return Temp;}

USART1_Config();/* ADIS spi初始化 */SPI_FLASH_Init();/* Get SPI Flash Device ID */PROD_ID = SPI_FLASH_ReadDeviceID();if (PROD_ID != 0x4068)   {    printf("rn     PROD_ID = 0x%X ", PROD_ID);    printf("rn     ADIS16488初始化失败");    while(PROD_ID != 0x4068)         {          PROD_ID = SPI_FLASH_ReadDeviceID();          printf("rn     PROD_ID = 0x%X ", PROD_ID);          }     }printf("rn     PROD_ID = 0x%X ", PROD_ID);printf("rn     ADIS16488初始化成功");