【BW20-12F Dev Board Evaluation】4. Virtual File System (VFS)

For related documentation, please refer to:https://aiot.realmcu.com/cn/latest/rst_rtos/rst_sdk/0_file_system/index.html#common-file-operation

The underlying implementation of the Virtual File System (VFS) includes FatFS and LittleFS.VFS provides common file operation interfaces such as fopen, fclose, fwrite, and fread.The Key-Value (KV) interface is implemented based on these common file operations.

The following example demonstrates how to implement VFS using LittleFS.

1. Create a file system BIN file using vfs.py

Package vgs_test.txt from the test directory into a BIN file.

Content of vgs_test.txt:

this is a vfs test. 2025.11.18

Command: vfs.py -t LITTLEFS -s 4096 -c 32 -dir test -out littlefs.bin

Actual command used:

~/mcu/Ameba-rtos/ameba-rtos/tools/image_scripts/vfs.py -t LITTLEFS -s 4096 -c 32 -dir test -out littlefs.bin

Output:

littlefs.bin has been successfully generated.args:├─ type: LITTLEFS├─ block_size: 4096├─ block_count: 32├─ image_size: 131072├─ source_directory: test└─ output_image: littlefs.bin

2. menuconfig Configuration

Enable the option:Enable VGS LITTLEFS

3. Application Code

Reference example:

/ameba-rtos/component/example/storage/vfs

1）fats.conf

# This file is generated automatically by:
# python menuconfig.py -s ../component/example/storage/vfs/fatfs.conf

CONFIG_VFS_LITTLEFS_INCLUDED=y // Use LITTLEFS

CONFIG_VFS_FATFS_INCLUDED=n

2）example_vfs.c

#include "ameba_soc.h"
#include "os_wrapper.h"
#include "vfs.h"
#include "example_vfs.h"
void example_vfs_thread(void *param)
{
rtos_time_delay_ms(3000);
char filename[] = "vfs_test.txt";
char path[128] = {0};
char buffer[32] = {0};
char *prefix;
FILE *finfo;
int res = 0;
(void)param;
RTK_LOGS(NOTAG, RTK_LOG_INFO, "\r\n====================Example: VFS====================\r\n");
prefix = find_vfs_tag(VFS_REGION_1);
DiagSnPrintf(path, sizeof(path), "%s:%s", prefix, filename);
finfo = fopen(path, "r");
if (finfo == NULL) {
RTK_LOGS(NOTAG, RTK_LOG_ERROR, "[%s] fopen() failed\r\n", __FUNCTION__);
goto exit;
}
res = fread(buffer, 128, 1, finfo);
if (res < 0) {
RTK_LOGS(NOTAG, RTK_LOG_ERROR, "[%s] fread() failed, err is %d\r\n", __FUNCTION__, res);
} else {
RTK_LOGS(NOTAG, RTK_LOG_ERROR, "[%s] fread() content, read buffer is %s\r\n", __FUNCTION__, buffer);
}
fclose(finfo);
exit:
rtos_task_delete(NULL);
}
void example_vfs(void)
{
if (rtos_task_create(NULL, ((const char *)"example_vfs_thread"), example_vfs_thread, NULL, 4096 * 4, 1) != RTK_SUCCESS) {
RTK_LOGS(NOTAG, RTK_LOG_ERROR, "\n\r%s rtos_task_create(example_vfs_thread) failed", __FUNCTION__);
}
}​

prefix = find_vfs_tag(VFS_REGION_1); // Get the VFS1 tag

DiagSnPrintf(path, sizeof(path), "%s:%s", prefix, filename); // Build file path

finfo = fopen(path, "r"); // Open file

res = fread(buffer, 128, 1, finfo); // Read file

4. Flash Programming

For the VFS Flash region, the StartAddr and EndAddr configuration should follow:Actual end address = EndAddr + 1

5. Execution Result

UART output

The output shows that the system successfully reads the content of vfs_test.txt from the file system flashed from littlefs.bin, and prints it via the serial port.