Unable to Mount LittleFS File System On External Flash On NRF54L15-DK

[Khalil Tawosli]

Hi everyone,

I'm new to both nRF Connect SDK and Zephyr RTOS, and I’m trying to modify the official LittleFS FileSystem Sample to mount an external SPI flash as the storage backend.

So far, I haven't been successful in getting it to work.

I've attached the relevant files:

• .overlay file with external flash node

• prj.conf with the necessary config options

• boards/<board_name>.yaml if needed

I'd really appreciate any advice, corrections, or working examples from anyone who has managed to get LittleFS working on external flash (especially using nordic,pm-ext-flash or similar).

Thanks in advance for your help!

Best regards,
Khalil

pm_static.yaml

nrf54l15dk_nrf54l15_cpuapp.conf2860.nrf54l15dk_nrf54l15_cpuapp.overlay

[Hieu]

Hello Khalil,

Could you please follow these steps:

1. Remove your pm_static.yml from the project
2. Build pristine once
3. Verify that features in this build work. Stop here if this step failed.
4. Copy the partitions.yml from that build directory as a new pm_static.yml
5. Reconfigure the littlefs partition to external flash, remember to add some properties under the partitions as followed:
   affiliation:
     -disk
   extra_params: {
       disk_name: "littlefs",
       disk_cache_size: 4096,
       disk_sector_size: 512,
       disk_read_only: 0
     }
   
   Here is an example:
   littlefs_storage:
     address: 0xe7600
     end_address: 0x800000
     region: external_flash
     device: mx25r6435f
     size: 0x718000
     affiliation:
       -disk
     extra_params: {
         disk_name: "littlefs",
         disk_cache_size: 4096,
         disk_sector_size: 512,
         disk_read_only: 0
       }

Hieu

[Khalil Tawosli]

Thank you, Hieu, for your prompt response.

I tried implementing your suggestion, but unfortunately, the modified LittleFS sample still throws the following runtime error:

Sample program to r/w files on littlefs
E: FAIL: unable to find flash area 1: -2

I: littlefs partition at /lfs1
I: LittleFS version 2.9, disk version 2.1
E: can't open flash area 1
E: fs mount error (-19)
E: Automount /lfs1 failed: -19

Below is the compiled partitions.yaml output after applying your changes:

app:
address: 0x0
end_address: 0x165000
region: flash_primary
size: 0x165000
bootconf:
address: 0xffd080
end_address: 0xffd084
region: bootconf
size: 0x4
external_flash:
address: 0x6000
end_address: 0x800000
region: external_flash
size: 0x7fa000
littlefs_storage:
address: 0x0
device: DT_CHOSEN(nordic_pm_ext_flash)
end_address: 0x6000
placement:
before:
- tfm_storage
- end
region: external_flash
size: 0x6000
otp:
address: 0xffd500
end_address: 0xffd9fc
region: otp
size: 0x4fc
sram_primary:
address: 0x20000000
end_address: 0x2002f000
region: sram_primary
size: 0x2f000

And here's the pm_static.yaml content I'm using:

littlefs_storage:
address: 0xe7600
end_address: 0x800000
region: external_flash
device: mx25r6435f
size: 0x718000
affiliation:
-disk
extra_params: {
disk_name: "littlefs",
disk_cache_size: 4096,
disk_sector_size: 512,
disk_read_only: 0
}

It’s worth noting that the generated partitions.yaml looks exactly the same even when I used a simplified pm_static.yaml like this:

littlefs_ext_storage:
address: 0x00000000
size: 0x00800000
region: external_flash
placement:
before: end

I’m still stuck and wondering if you or anyone else could share a working sample project targeting the nRF54L15-DK that successfully mounts LittleFS on external SPI flash. That would be incredibly helpful for learning and troubleshooting.

Thanks again for your support!

Best regards,
Khalil