Cannot get SPI communication with SD Card to work (but works on arduino)

[estedebain]

Hi everyone,

I'm trying to interface an SD card over SPI with an STM32F411. However, I cannot even initialize it. My current sequence is:

1. Wait 20 ms after power-on.

2. Send 10 clock cycles with CS high.

3. Pull CS low and send CMD0 and wait for a reponse.

Instead, I only ever receive 0xFF instead of 0x01.

My SPI configuration looks like this:

Here is the relevant code:

    MY_DEBUG_PRINTLN("Hello World");

    uint8_t txBuf[6];
    uint8_t resp = 0x00;
    uint8_t dummy = 0xFF;

    HAL_Delay(20);

    MY_DEBUG_PRINT("Raw SD SPI test:\n");

    // send 80 clocks with CS high
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET);
    for (int i = 0; i < 10; i++) {
        HAL_SPI_Transmit(&hspi2, &dummy, 1, HAL_MAX_DELAY);
    }
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET);

    // CMD0 frame
    txBuf[0] = 0x40;
    txBuf[1] = 0x00;
    txBuf[2] = 0x00;
    txBuf[3] = 0x00;
    txBuf[4] = 0x00;
    txBuf[5] = 0x95;

    // send command
    HAL_SPI_Transmit(&hspi2, txBuf, 6, HAL_MAX_DELAY);

    // wait for response
    for (int i = 0; i < 30; i++) {
        HAL_SPI_TransmitReceive(&hspi2, &dummy, &resp, 1, HAL_MAX_DELAY);
        MY_DEBUG_PRINTF("resp = 0x%02X\r\n", resp);
        if ((resp & 0x80) == 0) break;
    }

    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET);

    MY_DEBUG_PRINTF("CMD0 resp = 0x%02X\r\n", resp);

Output:
Hello World
Raw SD SPI test:
resp = 0xFF

... (30 times)

resp = 0xFF

CMD0 resp = 0xFF

On arduino if I execute the "same" code it works:

  Serial.begin(115200);
  while (!Serial) {}

  Serial.println("Hello World");

  uint8_t txBuf[6];
  uint8_t resp = 0x00;
  uint8_t dummy = 0xFF;

  // SPI init
  SPI.begin();
  SPI.beginTransaction(SPISettings(100000, MSBFIRST, SPI_MODE0));

  pinMode(SD_CS_PIN, OUTPUT);
  digitalWrite(SD_CS_PIN, HIGH);

  delay(20);

  Serial.println("Raw SD SPI test:");

  // send 80 clocks with CS high
  for (int i = 0; i < 10; i++) {
    SPI.transfer(dummy);
  }

  digitalWrite(SD_CS_PIN, LOW);

  // CMD0 frame
  txBuf[0] = 0x40; 
  txBuf[1] = 0x00;
  txBuf[2] = 0x00;
  txBuf[3] = 0x00;
  txBuf[4] = 0x00;
  txBuf[5] = 0x95;

  // send the command frame
  for (int i = 0; i < 6; i++) {
    SPI.transfer(txBuf[i]);
  }

  // wait for response (max 30 tries)
  for (int i = 0; i < 30; i++) {
    resp = SPI.transfer(dummy);
    Serial.print("resp = 0x");
    Serial.println(resp, HEX);
    if ((resp & 0x80) == 0) break;
  }

  digitalWrite(SD_CS_PIN, HIGH); 
  SPI.transfer(dummy);           

  Serial.print("CMD0 resp = 0x");
  Serial.println(resp, HEX);

  SPI.endTransaction();

Output is:

Hello World
Raw SD SPI test:
resp = 0xFF
resp = 0x1
CMD0 resp = 0x1

I am running out of Ideas :(.

[Saket_Om]

Hello @estedebain 

Did you try to check what happening on the bus using logic analyser? Is the SPI sending the CMD?

[estedebain · Accepted solution]

Hello Saket_om,

So in the end it randomly started working, after connecting it to an oscilloscope, the signals look similar. Maybe some jumper cable was broken? 

Thank you!