SPI Sends Dummy bytes

[pranathi1091]

Posted on March 05, 2013 at 14:32

Hello All,

I am using STM32F207VC. I have problem while sending data to slaves. I send a packet of data for example 0x01,0x02,0x03,0x04,0x05,0x06. While sending these packets SPI sends 0x00 in between anyof these data and my actual data is skipped.So My Slave doesnt understand what I am sending and its not responding. Could any one pls let me know what could be the problem. I am stuck with this since last 2 days. Here is my code

uint8_t SPIWrite(uint8_t *pBufferPtr, uint8_t ucSPIPacketLength)

{

 uint8_t ucCount;

    uint8_t ucDummyRead;      /*Assert the CS Pin to Low for SPI Slave*/     CS_LOW(GPIOB,GPIO_Pin_12);            Delayus(100);        for (ucCount=0; ucCount < ucSPIPacketLength; ucCount++)    {   while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) != SET);      SPI_I2S_SendData(SPI2,*pBufferPtr );   if(SPI2->DR != *pBufferPtr)   {    SPI_I2S_SendData(SPI2,*pBufferPtr );   } ucDummyRead =SPI_I2S_ReceiveData(SPI2);   /*wait for transmission to complete */               while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) != SET);   Delayus(100);   /*read the response from the spi rx buffer to dummy variable*/   ucDummyRead =SPI_I2S_ReceiveData(SPI2);  while(SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET) ;     pBufferPtr++;              }       CS_HIGH(GPIOB,GPIO_Pin_12);

    return SUCCESS;

    } #st

[Tesla DeLorean]

Posted on March 05, 2013 at 14:40

Don't do this

 if(SPI2->DR != *pBufferPtr)   {    SPI_I2S_SendData(SPI2,*pBufferPtr );   } Reading DR relects data in the RECEIVE buffer not the SEND buffer, stop doing this.