I got the Zephyr littlefs sample on the nRF5340 DK to build, but never gets to main().

[mperry_at_scram]

I attempted to port the littlefs sample to the nRF5340 Developer Kit. I've gotten it to build but when I flash it there is no log output. When I try to debug it the startup process looks normal but I never hit a breakpoint I set in main().

After searching, I found this post ( littlefs sample on nrf5340dk not running) and tried building and running the modified example "littlefs2" from that thread. Same result: it never seems to get to main().

I succeeded in getting the flash_jesd216 built and running correctly on the nRF5340 DK, as well as my own app to write to the external flash and do a read back to verify. So I know the hardware and my development environment are basically good.

I'm using nRF Connect SDK v2.1.0 installed from the Toolchain Manager (v1.2.0). I'm running Ubuntu 20.04.5 LTS. I have nRF5340 DK hardware rev 2.0.0. I've attached zip archives of both of my attempts at getting this working.

7142.littlefs2.zip1581.littlefs.zip

[David Boden]

Just to declare up-front I'm new to embedded software, but not to programming in general; sorry if I've misunderstood anything. I'm using NRF Connect v2.2.0.

I have the same objective as the original poster, @mperry_at_scram, getting the littlefs filesystem up on the *external* flash.

It's important that we build with `prj_blk.conf`, because this is the config which communicates the intention of using the external 64MB flash for the filesystem rather than the SOC's internal flash.

This littlefs sample is really two samples in one, which is definitely a source of confusion.

@Naeem Maroof , when I run your example when building against board `nrf5340dk_nrf5340_cpuapp` (notice no `_ns` suffix) then I get this, which works. However, it's using the *internal* flash (notice `FS at flash-controller`...):

```

*** Booting Zephyr OS build v3.2.99-ncs1 ***

Sample program to r/w files on littlefs

Area 6 at 0xfa000 on flash-controller@39000 for 24576 bytes

I: LittleFS version 2.5, disk version 2.0

I: FS at flash-controller@39000:0xfa000 is 6 0x1000-byte blocks with 512 cycle

I: sizes: rd 16 ; pr 16 ; ca 64 ; la 32

I: /lfs mounted

/lfs mount: 0

/lfs: bsize = 16 ; frsize = 4096 ; blocks = 6 ; bfree = 3

... logs indicating successful execution...

```

In your zip file you've included the file `nrf5340dk_nrf5340_cpuapp_ns.overlay` (with `_ns` suffix), which I don't think was what you intended? (again, sorry if I've misunderstood)

If I copy this to `nrf5340dk_nrf5340_cpuapp.overlay` (without `_ns` suffix) and build / flash then I get:

```

I: littlefs partition at /lfs1

I: LittleFS version 2.5, disk version 2.0

I: FS at mx25r6435f@0:0x0 is 16 0x1000-byte blocks with 512 cycle

I: sizes: rd 16 ; pr 16 ; ca 64 ; la 32

E: WEST_TOPDIR/modules/fs/littlefs/lfs.c:4196: Invalid block count (32 != 16)

W: can't mount (LFS -22); formatting

E: ***** USAGE FAULT *****

E: Stack overflow (context area not valid)

E: r0/a1: 0x00000000 r1/a2: 0x00000667 r2/a3: 0x00000000

E: r3/a4: 0x00000000 r12/ip: 0x00000020 r14/lr: 0x00004525

E: xpsr: 0x00000000

E: Faulting instruction address (r15/pc): 0x00004235

E: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0

E: Current thread: 0x20000418 (unknown)

E: Halting system

```

Hooray, this is trying to use the external flash, `FS at mx25r6435f@0:0x0`... but is failing due to "Invalid block count". I'd be grateful if you could confirm that you see the same thing, and I'd appreciate any pointers towards fixing it that might spring to mind.

As a side-issue, which I'm not concerned about myself, if I build for board `nrf5340dk_nrf5340_cpuapp_ns` with `prj_blk.conf` then it tries to use the internal SOC flash and this prompts a different error, which I've seen elsewhere on the forums.

```

I: littlefs partition at /lfs1

I: LittleFS version 2.5, disk version 2.0

I: FS at flash-controller@39000:0xf8000 is 6 0x1000-byte blocks with 512 cycle

I: sizes: rd 16 ; pr 16 ; ca 64 ; la 32

E: WEST_TOPDIR/modules/fs/littlefs/lfs.c:1234: Corrupted dir pair at {0x0, 0x1}

W: can't mount (LFS -84); formatting

```

It would be really useful to get the Zephyr sample updated with the nrf5340 configurations just so that anyone who is trying to do the same thing doesn't need to see all of this :) github.com/.../boards

[Naeem Maroof]

Hello David,

Apologies for delayed response.

You are very much right for all the items you have mentioned.

We can see that "prj_blk.conf" has configurations related to disk access; so yes, we need to use these configurations if we are using off-chip storage.

Regarding the overlay file, we need to include the file with correct name as of the target.

Nonetheless, when building for _ns target, TFM is included. So you need to see what do you want.

I do not have a SDCard with me, but looks like the formatting problem of the card. 

(Formatting of SD card)

Good to know that it is working for you and thank you for your input.

Regards,

Naeem

[David Boden]

It works when I run the sample in littlefs2.zip provided by Sigurd Hellesvik attached to this thread:  littlefs sample on nrf5340dk not running 

This sample only has a prj.conf and is significantly different than the latest version of the littlefs sample. The sample looks to have changed significantly, the latest being https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/subsys/fs/littlefs

I suspect there's a problem with the sample distributed with the latest nRF Connect SDK when trying to run prj_bulk.conf with an NRF5340 DK board, after copying the overlay configuration files over from the NRF52 examples.