STM32 SPI发送数据示波器信号的问题

kingchunhai

   我使用STM32 的SPI发送数据使用示波器测量MOSI 有数据波形，但是MISO脚竟然也有同频率的波形，什么回事？程序如下：
    void  SPI2_Init(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

  SPI_InitTypeDef  SPI_InitStructure;

RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA, ENABLE ); 

RCC_APB2PeriphClockCmd( RCC_APB2Periph_SPI1,  ENABLE );

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;            //???????ì????

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_SetBits(GPIOA,GPIO_Pin_5|GPIO_Pin_6|GPIO_Pin_7);  

SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex; //???????ò?????¤

SPI_InitStructure.SPI_Mode = SPI_Mode_Master; //SPI   mode  master

SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b; //8  bit  dataframe

SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;

SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge; //?±???à?????ù?±??

SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

//SPI1->CR1&=0xfcff;

    //SPI1->CR1|=(1<<9);

//SPI1->CR1|=(1<<8);

SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_256; //baund  prescaler  256

SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB; //data transfer start of MSB

SPI_InitStructure.SPI_CRCPolynomial = 7; //CRC?à????

SPI_Init(SPI1, &SPI_InitStructure);  

SPI_Cmd(SPI1, ENABLE); 

//SPI2_ReadWriteByte(0xff);   //start transmission    

}

u8 SPI2_ReadWriteByte(u8 TxData)

{

u8 retry=0;

while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET) //send  buffer empty

{

retry++;

if(retry>200)return 0;

}  

   SPI_I2S_SendData(SPI1, TxData); //?¨?????è·???????????

retry=0;

   

}

int main(void)

{

  delay_init();

  NVIC_Configuration();

  SPI2_Init();

  while(1)

  {

 

  SPI2_ReadWriteByte(0x55);  

    }

}

兄弟们指点一下啊

正点原子

外设接的什么？

kingchunhai

SPI协议的片子MFRC522

kingchunhai

请问一下，SPI的SCK 、MOSI、MISO应该设成推挽输出还是加上上拉电阻设成开漏输出啊？