SD card

The Logic v2 board has an sdcard slot which you can use to store or load data from FAT32-formatted cards.

Info

The 1.x HW revisions do not have SD card slot.

SDMMC is broken

On the 2.0 HW revision, the SDMMC mode is broken. You have to use SDSPI protocol to access the SD card. This will be fixed in a later HW revision.

Pinout

Pin	SD SPI	SD MMC
11	MOSI	CMD
12	SCLK	CLK
13	MISO	D0
3	CS	CD

Example init code

The SD card has some long-ish init code, but after that, you may use standard C or C++ functions to access the filesystem, just like on a desktop.

#include "Logic.hpp"
#include <iostream>

#include "esp_vfs_fat.h"
#include <dirent.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/unistd.h>

#define EXAMPLE_MAX_CHAR_SIZE 64

static const char* TAG = "example";

#define MOUNT_POINT "/sdcard"

void logicMain() {
    esp_err_t ret;

    // SPI BUS init
    spi_bus_config_t bus_cfg = {};
    bus_cfg.mosi_io_num = GPIO_NUM_11;
    bus_cfg.miso_io_num = GPIO_NUM_13;
    bus_cfg.sclk_io_num = GPIO_NUM_12;
    bus_cfg.quadwp_io_num = -1;
    bus_cfg.quadhd_io_num = -1;
    bus_cfg.max_transfer_sz = 4000;

    ret = spi_bus_initialize(SPI2_HOST, &bus_cfg, SPI_DMA_CH_AUTO);
    if (ret != ESP_OK) {
        ESP_LOGE(TAG, "Failed to initialize bus.");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
        return;
    }

    /// FS options
    esp_vfs_fat_mount_config_t mount_config = {};
    mount_config.max_files = 5;
    mount_config.allocation_unit_size = 16 * 1024;

    sdmmc_card_t* card;
    const char mount_point[] = MOUNT_POINT;
    ESP_LOGI(TAG, "Initializing SD card");

    // SDSPI init
    sdmmc_host_t host = SDSPI_HOST_DEFAULT();
    host.slot = SPI2_HOST;

    sdspi_device_config_t dev_cfg = SDSPI_DEVICE_CONFIG_DEFAULT();
    dev_cfg.gpio_cs = GPIO_NUM_3;

    ESP_LOGI(TAG, "Mounting filesystem");
    ret = esp_vfs_fat_sdspi_mount(mount_point, &host, &dev_cfg, &mount_config, &card);

    if (ret != ESP_OK) {
        if (ret == ESP_FAIL) {
            ESP_LOGE(TAG, "Failed to mount filesystem. "
                          "If you want the card to be formatted, set the EXAMPLE_FORMAT_IF_MOUNT_FAILED menuconfig option.");
        } else {
            ESP_LOGE(TAG, "Failed to initialize the card (%s). "
                          "Make sure SD card lines have pull-up resistors in place.",
                esp_err_to_name(ret));
        }
        return;
    }
    ESP_LOGI(TAG, "Filesystem mounted");

    // List root directory
    DIR* dir = opendir(mount_point);
    struct dirent* ent;
    while ((ent = readdir(dir)) != NULL) {
        printf("File %s %d\n", ent->d_name, ent->d_type);
    }
    closedir(dir);

    while (true) {
        delay(100);
    }
}