SPI 的MiSO什么都不连，持续收到0Xff

xtong533 · 发表于 2016-8-10 09:18:02

继续做SPI的实验，Stm32F107VCT6的SPI1做主机，MISO放在那里，不接从机。结果接收数组里一直是0xff,这是为什么？
代码如下
#include "SPI1.h"

/* Private macro -------------------------------------------------------------*/
//#define SPI3_CS_LOW()       GPIO_ResetBits(GPIOA, GPIO_Pin_15) //片选引脚/CS拉低
//#define SPI3_CS_HIGH()       GPIO_SetBits(GPIOA, GPIO_Pin_15)  //片选引脚/CS拉高

#define BufferSize  8
#define ReSize       50
char SPI1_Buffer_Tx[BufferSize] = {0x01,0x02,0x04,0x08,0x10,0x11,0x20,0x40};
char SPI1_Buffer_Rx[ReSize] = {0x00};
/**-----------------------------------------------------------------
  * @函数名
  * @功能
  *
  * @参数无
  * @返回值无
***----------------------------------------------------------------*/

void SPI1_Init(void)
{

SPI_InitTypeDef  SPI_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

/* 使能SPI1和GPIOA的RCC时钟*/
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB, ENABLE);

/* Configure SPI1 pins: SCK, MISO and MOSI --------------------------------*/
/*Pin5:SCK; Pin7:MOSI-------------------------------------------*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);

/* SPI1初始化配置*/
SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;  //主模式
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b; //SPI通信数据的大小
SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;       //时钟极性
SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge; //时钟相位
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;    //片选信号，软件模式
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_64; //SPI分频值，分频后的值为SCK的时钟频率
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB; //选择SPI通信时，是高位数据在前还是低位数据在前
SPI_InitStructure.SPI_CRCPolynomial = 7; //与CRC校验有关
SPI_Init(SPI1, &SPI_InitStructure);

/*使能SPI1 */
SPI_Cmd(SPI1, ENABLE);
}

//void SPI3_WriteData(char da);
//uint16_t SPI3_ReadData(void);

void SPI1_Test(void)
{
char Tx_Idx = 0, Rx_Idx = 0;
while(Tx_Idx < BufferSize)
{
      while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET);
      SPI_I2S_SendData(SPI1,SPI1_Buffer_Tx[Tx_Idx]);

      while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE)==RESET);
      SPI1_Buffer_Rx[Rx_Idx] = SPI_I2S_ReceiveData(SPI1);

      Tx_Idx++;
      Rx_Idx++;
}
/*拉高片选信号*/
//SPI3_CS_HIGH();
}

void SPI1_SendData(void)
{
char Tx_Idx = 0;
while(Tx_Idx < BufferSize)
{
      while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET);
      SPI_I2S_SendData(SPI1,SPI1_Buffer_Tx[Tx_Idx]);

//       while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE)==RESET);
//       SPI1_Buffer_Rx[Rx_Idx] = SPI_I2S_ReceiveData(SPI1);
      Tx_Idx++;
}
}

void SPI1_ReceiveData(void)
{
char Rx_Idx = 0;
// while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET);
// SPI_I2S_SendData(SPI1,0x11);
while(Rx_Idx < ReSize)
{
      while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET);
      SPI_I2S_SendData(SPI1,0x11);

      while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE)==RESET);
      SPI1_Buffer_Rx[Rx_Idx] = SPI_I2S_ReceiveData(SPI1);

         Rx_Idx++;
}

}

我在main函数里运行，SPI1_init ，和 SPI1_ReceiveData 函数。用keil仿真，看到SPI1_Buffer_Rx中全是0xff
哪位高手，能解释下原理。大家一起探讨探讨