SD_MMC sdcard driver for datalogger iot

Development Boards Arduino
1

The Sparkfun esp32 datalogger iot board is has exactly the hardware I want for my next project, including the 4-bit SDCard interface. I am developing the software in Platformio in an Arduino framework. Unfortunately, there is no board definition for the “sparkfun_esp32_datalogger_iot” so I am using the “sparkfun_esp32_iot_redboard” which is similar except for the spi sdcard interface. All the previously developed datalogging code from the redboard came over and is working as expected. However, when I include the SD_MMC driver the code hangs in the SD_MMC.begin() function and never returns. The code to that point is:

void setup() {
  int clk = 14;
  int cmd = 15;
  int d0 = 2;
  int d1 = 4;
  int d2 = 12;
  int d3 = 13;

  Serial.begin(115200);
  SD_MMC.setPins(clk, cmd, d0, d1, d2, d3);
  if (!SD_MMC.begin()) {
    Serial.println("Card Mount Failed");
    return;
  }

I have looked through the SD_MMC code but cannot see what the problem could be. I have tried the sd_card_example_main.c code from platforms\espressif\examples\espidf-storage-sdcard\src and while it assumes an espidf environment, I compiled it anyway and it fails with the messages:

Initializing SD card
Using SDMMC peripheral
Mounting filesystem
E (53) sdmmc_common: sdmmc_init_ocr: send_op_cond (1) returned 0x107
E (54) vfs_fat_sdmmc: sdmmc_card_init failed (0x107).

I am at a loss for what to try next. Sparkfun normally provide excellent get-you-going doco for their boards but for this one it is sadly missing.

Any help would be greatly appreciated.

Ron

2

For the SparkFun DataLogger IoT board, the SD card pins are:

CLK: GPIO14
CMD: GPIO15
D0: GPIO2
D1: GPIO4
D2: GPIO12
D3: GPIO13

These pin assignments match exactly with what you’ve already put in your code, which is correct/good.

There are a couple of important differences between the two boards that might be causing issues:

The DataLogger IoT uses a 4-bit SDIO interface, while the IoT RedBoard ESP32 uses a standard SPI interface for the SD card.
The DataLogger IoT includes additional components for the SD card interface:
There’s a 74HC4050D level shifter (U4) between the ESP32 and the SD card slot.
Each SD card line has a 10k pull-up resistor.

Given that your pin assignments are correct, the issue likely stems from the board definition or the SD card driver configuration.

Here are some suggestions:

Ensure you’re using the latest version of the ESP32 core and SD_MMC library in PlatformIO.

Try initializing the SD card without specifying pins:

if (!SD_MMC.begin("/sdcard", true)) {  // true for 1-bit mode, false for 4-bit mode
    Serial.println("Card Mount Failed");
    return;
}

If that doesn’t work, try explicitly setting the pins and specifying 4-bit mode:

SD_MMC.setPins(14, 15, 2, 4, 12, 13);
if (!SD_MMC.begin("/sdcard", false)) {  // false for 4-bit mode
    Serial.println("Card Mount Failed");
    return;
}

Make sure you’re using a compatible SD card (FAT32 formatted, 32GB or less). If these suggestions don’t resolve the issue, you may need to dig deeper into the SD_MMC library

For the IDF error: The error you’re seeing (0x107) typically indicates a timeout during the SD card initialization process. This could be due to incorrect pin assignments, hardware issues, or incompatible SD card.

3

Your comment about the 74HC4040D level shifter was the fix. I made GPIO32 an output, set it high and all works beautifully. Many thanks., Ron

4

Wahoo!