Reading worng first byte from serial flash

[moran]

Posted on May 18, 2015 at 09:43

Hi everyone,

I'm working on custom board connecting STM32L152 to MX25L8006E (serial flash) using SPI driver. The SS is handle by me (software). I'm writing 24 bytes to some address and when i read from same address the first byte is always 0xFF. It is not issue with serial flash because on the scope i can see that MISO signal is currect. Waht can be the issue ???? below you can find my Read/Write functions :

//Send

void SendDataSpiControl(BYTE a_data) {     //< Wait until the transmit buffer is empty   //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   while(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET)   {   }     //!< Send the byte  //~~~~~~~~~~~~~~~~~~~~~~~~~   SPI_I2S_SendData(SPI1, a_data);     //!< Wait to receive a byte  //~~~~~~~~~~~~~~~~~~~~~~~~~   while(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET){}         //!< Return the byte read from the SPI bus  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   //return SPI_I2S_ReceiveData(ETH_SPI);   }   //Receive uint8_t ReciveDataSpiControl(void) {   uint8_t Data = 0;      //!< Wait until the transmit buffer is empty  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET){}       //!< Send the byte  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   SPI_I2S_SendData(SPI1, SD_DUMMY_BYTE);         //!< Wait until a data is received  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET){}       //!< Get the received data  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   g_opSpiControl->m_receiveByte = SPI_I2S_ReceiveData(SPI1);     // !< Return the shifted data  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   return g_opSpiControl->m_receiveByte; } Thanks in advance, Moran

[Tesla DeLorean]

Posted on May 18, 2015 at 15:14

Consider the setting of RXNE, and if it reflects old stale data. ie try clearing it before sending.

[moran]

Posted on May 18, 2015 at 16:58

Thanks Clive it work.

I've add to receive function one read before sending the dummy byte . my SPI read code :

//Receive

uint8_t ReciveDataSpiControl(void) {   uint8_t Data = 0;      //!< Wait until the transmit buffer is empty  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET){}  

  // this read is only to clean the garbage from data register

  SPI_I2S_ReceiveData(SPI1);     //!< Send the byte  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   SPI_I2S_SendData(SPI1, SD_DUMMY_BYTE);         //!< Wait until a data is received  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET){}       //!< Get the received data  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   g_opSpiControl->m_receiveByte = SPI_I2S_ReceiveData(SPI1);     // !< Return the shifted data  //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   return g_opSpiControl->m_receiveByte; }