nrf52840 DK, nRF Connect SDK 2.3.0 using vsCode, FAT Filesystem Sample Application
Working with the FAT_FS sample code, I am able to communicate with the SD card perfectly fine, as far as I can tell. The call to lsdir() functions as expected. However, when calling fs_open() to open a file to write to on an external SD card, it is returning error code -2 IF the filepath (mount point + filename) is longer than 14 characters. If the filepath is less than 14 characters then it will successfully write data. I thought it might be resolved by enabling CONFIG_FS_FATFS_LFN, however it did not work. See the code below for my example.
What does error code -2 mean? I wasn't able to find a clear answer anywhere. Is it the same as ENOENT, found in /zephyr/lib/libc/minimal/include/errno.h?
If I get a little deeper with the error, it fails in fs.c at line 163, in fs_open.
fs.c (in the code snippet below the failure is at line 33)
/* File operations */
int fs_open(struct fs_file_t *zfp, const char *file_name, fs_mode_t flags)
{
struct fs_mount_t *mp;
int rc = -EINVAL;
if ((file_name == NULL) ||
(strlen(file_name) <= 1) || (file_name[0] != '/')) {
LOG_ERR("invalid file name!!");
return -EINVAL;
}
if (zfp->mp != NULL) {
return -EBUSY;
}
rc = fs_get_mnt_point(&mp, file_name, NULL);
if (rc < 0) {
LOG_ERR("mount point not found!!");
return rc;
}
if (((mp->flags & FS_MOUNT_FLAG_READ_ONLY) != 0) &&
(flags & FS_O_CREATE || flags & FS_O_WRITE)) {
return -EROFS;
}
CHECKIF(mp->fs->open == NULL) {
return -ENOTSUP;
}
zfp->mp = mp;
rc = mp->fs->open(zfp, file_name, flags);
if (rc < 0) {
LOG_ERR("file open error (%d)", rc);
zfp->mp = NULL;
return rc;
}
/* Copy flags to zfp for use with other fs_ API calls */
zfp->flags = flags;
return rc;
}
main.c
#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/storage/disk_access.h>
#include <zephyr/logging/log.h>
#include <zephyr/fs/fs.h>
#include <ff.h>
static FATFS fat_fs;
/* mounting info */
static struct fs_mount_t mp = {
.type = FS_FATFS,
.fs_data = &fat_fs,
};
static const char *disk_mount_pt = "/SD:";
void main(void)
{
mp.mnt_point = disk_mount_pt;
int res = fs_mount(&mp);
if (res == FR_OK) {
printk("Disk mounted.\n");
lsdir(disk_mount_pt);
} else {
printk("Error mounting disk.\n");
}
char datatest[] = "1,2,3,4,5,6\n";
size_t datatest_size = strlen(datatest);
struct fs_file_t dfile;
size_t written_size = 0;
fs_file_t_init(&dfile);
// This is where the code fails.
res = fs_open(&dfile, "/SD:/DKlog.txt", FS_O_RDWR | FS_O_APPEND);
if(res < 0)
return false;
written_size = fs_write(&dfile, datatest, datatest_size);
res = fs_close(&dfile);
while (1) {
ret = toggle_leds();
k_msleep(SLEEP_TIME_MS);
}
}
Relevant prj.conf settings
CONFIG_DISK_ACCESS=y CONFIG_FILE_SYSTEM=y CONFIG_FAT_FILESYSTEM_ELM=y CONFIG_DISK_DRIVER_SDMMC=y CONFIG_FS_FATFS_LFN=y CONFIG_MAIN_STACK_SIZE=4096 CONFIG_SPI=y
