Logging on nRF54L15 to internal flash

Products & Technology XIAO
1

Does anyone have an example of writing logging to internal flash for nRF54L15?

I tried finding how to create the partition in the overlay file but no luck.

The prj.conf for littlefs and then usb to pull out the data later were:

# Flash and File System
CONFIG_FLASH=y
# Using NRF_QSPI_NOR is for external flash, for internal we use:
CONFIG_FLASH_MAP=y
CONFIG_FLASH_HAS_DRIVER_ENABLED=y
CONFIG_NRF_RRAM_WRITE_BUFFER_SIZE=16
CONFIG_FILE_SYSTEM=y
CONFIG_FILE_SYSTEM_LITTLEFS=y

# USB Support for downloading
CONFIG_USB_DEVICE_STACK=y
CONFIG_USB_DEVICE_PRODUCT="Xiao_nRF54_Logger"
CONFIG_UART_LINE_CTRL=y 
CONFIG_SERIAL=y
CONFIG_UART_INTERRUPT_DRIVEN=y
2

Hi there,

So, If this is for nRF54L15 internal nonvolatile logging, I would actually suggest ZMS first instead of LittleFS.

The reason is that Zephyr’s ZMS is intended for storage technologies including RRAM/MRAM-style memory that does not require erase-before-write, and Nordic has nRF54L-specific documentation for enabling ZMS in applications. That makes it a better fit for structured internal logging on nRF54L devices than starting with a full file system.

If you only need to store log records or key/value data, ZMS or NVS is usually simpler than LittleFS. LittleFS is still possible, but then you need to define a flash partition in devicetree and mount the file system from that partition using Zephyr’s flash map / filesystem configuration.

For LittleFS, the missing piece is typically a fixed-partitions entry in the overlay, something like a storage_partition under &flash0, plus the usual:

CONFIG_FLASH=y
CONFIG_FLASH_MAP=y
CONFIG_FILE_SYSTEM=y
CONFIG_FILE_SYSTEM_LITTLEFS=y

Zephyr’s flash map docs and LittleFS sample show that pattern.

Also, if you already have J-Link + RTT, I would use that first for development instead of adding USB right away. It is much easier to validate the logging pipeline with RTT before worrying about exporting files over USB.

So my suggestion would be:

  1. Use RTT for live debug output
  2. Use ZMS for internal persistent logs
  3. Add USB later only if you really need bulk extraction

Not aLittleFS example specifically, but Here is the exact overlay and prj.conf layout for a storage_partition on internal flash.
the missing piece is usually a storage partition in the overlay.
This is the general pattern you are looking for:

/ {
    chosen {
        zephyr,flash = &flash0;
    };
};

&flash0 {
    partitions {
        compatible = "fixed-partitions";
        #address-cells = <1>;
        #size-cells = <1>;

        storage_partition: partition@70000 {
            label = "storage";
            reg = <0x00070000 0x00010000>;
        };
    };
};

Important warning

Those addresses are example values only.

You must pick a region that does not overlap:

  • application image
  • MCUboot slots
  • settings storage
  • any existing board-defined partitions

That part matters. On Zephyr, the flash map comes directly from those DTS partitions.

Minimal prj.conf for LittleFS

The config can be trimmed to something like this to start:

CONFIG_FLASH=y
CONFIG_FLASH_MAP=y
CONFIG_FILE_SYSTEM=y
CONFIG_FILE_SYSTEM_LITTLEFS=y

Then build up from there. :+1:
If this is for internal persistent logging on nRF54L15, I would actually suggest ZMS first, not LittleFS.
Nordic has an nRF54L-specific ZMS guide, and Zephyr now recommends NVS and ZMS as the preferred non-filesystem backends for persistent storage. That makes ZMS a better fit if your goal is to store log/event records in internal memory and read them back later.

HTH
GL :slight_smile: PJ :v: