stm32f2 spi和外部芯片通信的问题。

#include <spi.h>



void Spi2_4438_Init(void)

{

  GPIO_InitTypeDef GPIO_InitStructure;

  SPI_InitTypeDef SPI_InitStructure;

  /* 使能gpio时钟和SPI2 */

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

  /*  Enable SCK, MOSI, MISO and NSS GPIO clocks using RCC_AHB1PeriphClockCmd()*/

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);    //?

  /* Connect PB12 to SPI2_SCK */

  GPIO_PinAFConfig(GPIOB, GPIO_PinSource12, GPIO_AF_SPI2);                            

  /* Connect PB14 to SPI2_MISO */

   GPIO_PinAFConfig(GPIOB, GPIO_PinSource14, GPIO_AF_SPI2);

  /* Connect PB15 to SPI2_MOSI */

  GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_SPI2);

  

  

  /* Configure SPI2 pins as alternate function (No need to

  configure PB13 since NSS will be managed by software) */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12|GPIO_Pin_14|GPIO_Pin_15;

  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(GPIOB, &GPIO_InitStructure);



  

  /*spi CONFIGURATION*/

  SPI_Cmd(SPI2, DISABLE);      //使能SPI2

  SPI_InitStructure.SPI_Direction =SPI_Direction_2Lines_FullDuplex; //双线输入输出全双工模式

  SPI_InitStructure.SPI_Mode = SPI_Mode_Master; //设置为SPI的主机模式

  SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b; //SPI数据大小：发送8位帧数据结构

  SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;   //设备空闲状态时同步时钟SCK的状态，High表示高电平，Low表示低电平

  SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;  //时钟相位，1表示在同步时钟SCK的奇数沿边采样，2表示偶数沿边采样

  SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;     //NSS由软件控件片选

  SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;//时钟的预分频值

  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;  //MSB高位在前

  SPI_InitStructure.SPI_CRCPolynomial = 7;     //CRC较验和的多项式

  SPI_Init(SPI2, &SPI_InitStructure);   //初始化SPI2的配置项

  SPI_Cmd(SPI2, ENABLE);      //使能SPI2

}



void main(void)

{ 

 // init_gpled();   //亮灯

   

 //  初始化spi

    uint16_t tmp;

    tmp=5;

    Spi2_4438_Init();

    

    while(SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET)

    {

    }

    SPI_I2S_SendData(SPI2,0);

    while(SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET)

    {

    }

    SPI_I2S_ReceiveData(SPI2);

    while(SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET)

    {

    }

    SPI_I2S_SendData(SPI2,0x0c);

    while(SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET)

    {

    }

    tmp=SPI_I2S_ReceiveData(SPI2);

    if(tmp!=0)

    {

        init_gpled();

    }

}