feat(storage/fatfs): add minimal FatFS example

examples/storage/fatfs_basic/main/fat_example_main.c

@@ -0,0 +1,87 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "esp_vfs.h"
+#include "esp_vfs_fat.h"
+#include "sdkconfig.h"
+
+static const char *TAG = "example";
+
+// Mount path for the partition
+const char *base_path = "/spiflash";
+
+// Handle of the wear levelling library instance
+static wl_handle_t s_wl_handle = WL_INVALID_HANDLE;
+
+void app_main(void)
+{
+    ESP_LOGI(TAG, "Mounting FAT filesystem");
+    // To mount device we need name of device partition, define base_path
+    // and allow format partition in case if it is new one and was not formatted before
+    const esp_vfs_fat_mount_config_t mount_config = {
+            .max_files = 4, // Number of files that can be open at a time
+            .format_if_mount_failed = true, // If true, try to format the partition if mount fails
+            .allocation_unit_size = CONFIG_WL_SECTOR_SIZE, // Size of allocation unit, cluster size.
+            .use_one_fat = false, // Use only one FAT table (reduce memory usage), but decrease reliability of file system in case of power failure.
+    };
+
+    esp_err_t err = esp_vfs_fat_spiflash_mount_rw_wl(base_path, "storage", &mount_config, &s_wl_handle);
+
+    if (err != ESP_OK) {
+        ESP_LOGE(TAG, "Failed to mount FATFS (%s)", esp_err_to_name(err));
+        return;
+    }
+
+    ESP_LOGI(TAG, "Filesystem mounted");
+
+    ESP_LOGI(TAG, "Opening file");
+
+    const char *filename = "/spiflash/example.txt";
+
+    FILE *f = fopen(filename, "wb");
+    if (f == NULL) {
+        perror("fopen");
+        ESP_LOGE(TAG, "Failed to open file for writing");
+        return;
+    }
+
+    fprintf(f, "This is written by the device");
+    fclose(f);
+
+    ESP_LOGI(TAG, "File written");
+
+    // Open file for reading
+    ESP_LOGI(TAG, "Reading file");
+
+    f = fopen(filename, "r");
+    if (f == NULL) {
+        ESP_LOGE(TAG, "Failed to open file for reading");
+        return;
+    }
+
+    char line[128];
+
+    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);
+
+    // Unmount FATFS
+    ESP_LOGI(TAG, "Unmounting FAT filesystem");
+
+    ESP_ERROR_CHECK(esp_vfs_fat_spiflash_unmount_rw_wl(base_path, s_wl_handle));
+
+    ESP_LOGI(TAG, "Done");
+}