Thẻ nhớ

../_images/sdcard.jpg

Board mạch ESP32 IoT Uno hỗ trợ thẻ nhớ chế độ 1-bit data, dễ dàng sử dụng với ví dụ của ESP-IDF

Ví dụ bên dưới sẽ khởi động, mount sdcard và sử dụng posix api kết hợp vfs để mở file, ghi, và đóng file

Lưu ý, khi sử dụng với board ESP32 IoT Uno cần sử dụng chế độ 1-bit:

host.flags = SDMMC_HOST_FLAG_1BIT;

Biên dịch dự án mẫu

git clone https://github.com/esp32vn/esp32-idf-sdcard.git
cd esp32-idf-sdcard
make flash monitor

Code

/* SD card and FAT filesystem example.
   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/

#include <stdio.h>
#include <string.h>
#include <sys/unistd.h>
#include <sys/stat.h>
#include "esp_err.h"
#include "esp_log.h"
#include "esp_vfs_fat.h"
#include "driver/sdmmc_host.h"
#include "driver/sdmmc_defs.h"
#include "sdmmc_cmd.h"

static const char* TAG = "example";

void app_main(void)
{
    ESP_LOGI(TAG, "Initializing SD card");

    sdmmc_host_t host = SDMMC_HOST_DEFAULT();

    // To use 1-line SD mode, uncomment the following line:
    host.flags = SDMMC_HOST_FLAG_1BIT;

    // This initializes the slot without card detect (CD) and write protect (WP) signals.
    // Modify slot_config.gpio_cd and slot_config.gpio_wp if your board has these signals.
    sdmmc_slot_config_t slot_config = SDMMC_SLOT_CONFIG_DEFAULT();

    // Options for mounting the filesystem.
    // If format_if_mount_failed is set to true, SD card will be partitioned and formatted
    // in case when mounting fails.
    esp_vfs_fat_sdmmc_mount_config_t mount_config = {
        .format_if_mount_failed = false,
        .max_files = 5
    };

    // Use settings defined above to initialize SD card and mount FAT filesystem.
    // Note: esp_vfs_fat_sdmmc_mount is an all-in-one convenience function.
    // Please check its source code and implement error recovery when developing
    // production applications.
    sdmmc_card_t* card;
    esp_err_t ret = esp_vfs_fat_sdmmc_mount("/sdcard", &host, &slot_config, &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 format_if_mount_failed = true.");
        } else {
            ESP_LOGE(TAG, "Failed to initialize the card (%d). Make sure SD card lines have pull-up resistors in place.", ret);
        }
        return;
    }

    // Card has been initialized, print its properties
    sdmmc_card_print_info(stdout, card);

    // Use POSIX and C standard library functions to work with files.
    // First create a file.
    ESP_LOGI(TAG, "Opening file");
    FILE* f = fopen("/sdcard/hello.txt", "w");
    if (f == NULL) {
        ESP_LOGE(TAG, "Failed to open file for writing");
        return;
    }
    fprintf(f, "Hello %s!\n", card->cid.name);
    fclose(f);
    ESP_LOGI(TAG, "File written");

    // Check if destination file exists before renaming
    struct stat st;
    if (stat("/sdcard/foo.txt", &st) == 0) {
        // Delete it if it exists
        unlink("/sdcard/foo.txt");
    }

    // Rename original file
    ESP_LOGI(TAG, "Renaming file");
    if (rename("/sdcard/hello.txt", "/sdcard/foo.txt") != 0) {
        ESP_LOGE(TAG, "Rename failed");
        return;
    }

    // Open renamed file for reading
    ESP_LOGI(TAG, "Reading file");
    f = fopen("/sdcard/foo.txt", "r");
    if (f == NULL) {
        ESP_LOGE(TAG, "Failed to open file for reading");
        return;
    }
    char line[64];
    fgets(line, sizeof(line), f);
    fclose(f);
    // strip newline
    char* pos = strchr(line, '\n');
    if (pos) {
        *pos = '\0';
    }
    ESP_LOGI(TAG, "Read from file: '%s'", line);

    // All done, unmount partition and disable SDMMC host peripheral
    esp_vfs_fat_sdmmc_unmount();
    ESP_LOGI(TAG, "Card unmounted");
}