STM32F4 : EEPROM 25LC256 management through SPI

Question

I am trying to drive a EEPROM Chip 25LC256 with a STM32F469I-DISCO but can't achieve it. I have tried to make my own function with HAL API bases but apparently something is wrong : I don't know if I write datas on the chip since I can't read it. Let me explain more.

So my chip is a DIP 25LC256 (DS is above is you wish). PINs HOLD and WP of EEPROM are tied to VCC (3.3V). PIN CS is connected to PH6 (ARD_D10 on board) and is managed by the software. PIN SI and PIN SO are respectively connected to PB15 (ARD_D11) and PB14 (ARD_D12) with the right alternate function (GPIO_AF5_SPI2). PIN SCK is also connected to PD3 (ADR_D13).

Here is my SPI configuration code :

EEPROM_StatusTypeDef ConfigurationSPI2(SPI_HandleTypeDef *spi2Handle){

  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOH_CLK_ENABLE();

  GPIO_InitTypeDef  gpioInit;

  ////  SCK [PD3]
  gpioInit.Pin =    GPIO_PIN_3;
  gpioInit.Mode =   GPIO_MODE_AF_PP;
  gpioInit.Pull =   GPIO_PULLDOWN;
  gpioInit.Speed =  GPIO_SPEED_FREQ_HIGH;
  gpioInit.Alternate = GPIO_AF5_SPI2;

  HAL_GPIO_Init(GPIOD, &gpioInit);

  //// MOSI [PB15]
  gpioInit.Pin =    GPIO_PIN_15;
  gpioInit.Pull =   GPIO_PULLUP;
  HAL_GPIO_Init(GPIOB, &gpioInit);

  //// MISO [PB14]
  gpioInit.Pin =    GPIO_PIN_14;
  gpioInit.Pull =   GPIO_NOPULL;
  HAL_GPIO_Init(GPIOB, &gpioInit);

  //// CS [PH6]
  gpioInit.Pin =    GPIO_PIN_6;
  gpioInit.Mode =   GPIO_MODE_OUTPUT_PP;
  gpioInit.Speed =  GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(GPIOH, &gpioInit);
  HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, GPIO_PIN_SET);

  //// SPI2

  __HAL_RCC_SPI2_CLK_ENABLE();

  spi2Handle->Instance = SPI2;

  spi2Handle->Init.Mode =               SPI_MODE_MASTER;
  spi2Handle->Init.Direction =          SPI_DIRECTION_2LINES;
  spi2Handle->Init.DataSize =           SPI_DATASIZE_8BIT;
  spi2Handle->Init.CLKPolarity =        SPI_POLARITY_LOW;
  spi2Handle->Init.CLKPhase =           SPI_PHASE_1EDGE;
  spi2Handle->Init.NSS =                SPI_NSS_SOFT;
  spi2Handle->Init.BaudRatePrescaler =  SPI_BAUDRATEPRESCALER_16;
  spi2Handle->Init.FirstBit =           SPI_FIRSTBIT_MSB;
  spi2Handle->Init.TIMode =             SPI_TIMODE_DISABLE;
  spi2Handle->Init.CRCCalculation =     SPI_CRCCALCULATION_DISABLE ;
  spi2Handle->Init.CRCPolynomial =      7;

  if(HAL_SPI_Init(spi2Handle) != HAL_OK){
      return EEPROM_ERROR;
  }

  return EEPROM_OK;
}

And two functions allowing respectively (and theorically) to WRITE and READ into the the chip :

Write Function :

EEPROM_StatusTypeDef WriteEEPROM(SPI_HandleTypeDef *spi2Handle, uint8_t *txBuffer, uint16_t size, uint16_t addr){

    uint8_t addrLow = addr & 0xFF;
    uint8_t addrHigh = (addr >> 8);

    uint8_t wrenInstruction = WREN_EEPROM; // Value : 0x06

    uint8_t buffer[32] = {WRITE_EEPROM, addrHigh, addrLow}; //Value : 0x02

    for(uint i = 0 ; i < size ; i++){
        buffer[3+i] = txBuffer[i];
    }

    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, RESET);
    if(HAL_SPI_Transmit(spi2Handle, &wrenInstruction, 1, TIMEOUT_EEPROM) != HAL_OK){
        return EEPROM_ERROR;;
    }
    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, SET);

    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, RESET);
    if(HAL_SPI_Transmit(spi2Handle, buffer, (size + 3), TIMEOUT_EEPROM) != HAL_OK){
        return EEPROM_ERROR;
    }
    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, SET);

    return EEPROM_OK;
}

Read Function :

EEPROM_StatusTypeDef ReadEEPROM(SPI_HandleTypeDef *spi2Handle, uint8_t *rxBuffer, uint16_t size, uint16_t addr){

    uint8_t addrLow = addr & 0xFF;
    uint8_t addrHigh = (addr >> 8);
    uint8_t txBuffer[3] = {READ_EEPROM, addrHigh, addrLow};

    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, RESET);

    HAL_SPI_Transmit(spi2Handle, txBuffer, 3, TIMEOUT_EEPROM);

    HAL_SPI_Receive(spi2Handle, rxBuffer, size, TIMEOUT_EEPROM);    

    HAL_GPIO_WritePin(GPIOH, GPIO_PIN_6, SET);

    return EEPROM_OK;
}

I know my function are not very "beautiful" but it was a first attempt. In my main, I have tried in the first place to write into the chip the data "0x05" at the 0x01 adress then to read this data back :

uint8_t bufferEEPROM[1] = {5};
uint8_t bufferEEPROM2[1] = {1};

WriteEEPROM(&spi2Handle, bufferEEPROM, 1, 0x01);
ReadEEPROM(&spi2Handle, bufferEEPROM2, 1, 0x01);

I have an oscilloscope so since it didn't work (monitoring with STM Studio) I visualized the CLK and SI PINs then CLK and SO PINs (can only see two channel at the same time) :

As you can see, with the first picture that shows CLK (yellow) and SI (or MOSI) in blue, I have all the data expected : The WRite ENable instruction then the WRITE instruction. Following the ADDRESS, then the DATA.

After that, the Read Function starts. First the READ instruction and the ADDRESS where I want to fetch the data. The last 8 bits are supposed to be the data stored at the address (0x01 in this case). Something happens on SI PIN but I guess this is because the HAL_SPI_Receive() function actually calls HAL_SPI_TransmitReceive() with my array bufferEEPROM2 as parameter (that's why we can se 0b00000001). And so it is because of my SPI configuration parameter (Full-duplex).

Anyway, theorically I am supposed to see 0b00000101 on SO PIN but as you can see in the second picture.... nothing.

I have tried to change gpioInit.Pull for SO PIN on PULLUP and PULLDOWN but nothing changed. NOPULL is because that's the last thing I have tried.

The thing is I don't know where to start. My transmission seems to work (but is it actually ?). Is there anything wrong with my initialization ? Acutally my main question would be : why I don't receive any data from my EEPROM ?

Many thanks !

Answer 1

Write operations need some time to complete (your datasheet says 5 ms on page 4), during that time no operation other than read status is possible. Try polling the status register with the RDSR (0x05) opcode to find out when it becomes ready (bit 0). You could also check the status (bit 1) before and after issuing WREN to see if it was successful.

Answer 2

So the problem is now solved. Here are the improvements :

There was actually two issues. The first one and certainly the most important is, as berendi stated, a timing issue. In my WRITE function I didn't let the time for the EEPROM to complete its write cycle (5 ms on datasheet). I added the following code line at the end of all my WRITE functions :

HAL_Delay(10); //10 ms wait for the EEPROM to complete the write cycle

The delay value could be less I think if time is preicous (theorically 5ms). I didn't test below 10 ms though. An other thing. With the oscilloscope I also saw that my Chip Select used to went HIGH in the middle of my last clock edge. I could not say if this could also imply some issues since that's a thing I solved in the first place by adding a code line before HAl_Delay(10). All my SPI transmission functions finishes this way now :

while(HAL_GPIO_ReadPin(CLK_PORT, CLK_PIN) == GPIO_PIN_SET){
}
HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);
HAL_Delay(10);

This way I have the proper pattern and I can write in the EEPROM and read back what I wrote.

NB : A last thing that made me goes deeper into my misunderstanding of the events : since my write functions didn't work, I focused on STATUS REGISTER write and read function (in order to solve this step by step). The write function didn't work either and in fact it was because the WRENbit wasn't set. I though (wrong one) that the fact to write into the STATUS REGISTER didn't ask also to set WREN like the WRITE functions into the memory ask to. Actually, it is also necessary.

Thanks for the help !