Update installed code by downloading .bin file from web server via Ethernet connection on Nano RP2040 Connect with mbed ?

[CantStopMyBrain]

By cobbling together bits from the examples for this library I thought I was going to pull this off: downloading an update .bin file from a web server to update a Nano RP2040 Connect running mbed and using an SPI-connected W5500 Ethernet shield for network connection. Should this be possible to do? Or are there obstacles/conflicts that make this particular combination -- NanoRP2040/mbed/SPI/ethernet/etc -- a non-starter?

I combined the download part of a download example with the "custom storage" example for the Nano RP2040 to get a file from a web server and save it to the on-board flash storage. Almost everything appears to be working: I get the .bin file and write it to flash without any errors, and then successfully restart/reboot the system, but it continues to run the existing sketch, not the new one it downloaded.

The download examples (and the ArduinoIoTCloud library which the CustomStorage example mentions) all perform some kind of .apply() and/or reset/reboot after downloading and saving the file. I've tried calling mbed_watchdog_trigger_reset(), NVIC_SystemReset(), and a reset method given here: https://gershnik.github.io/2024/02/12/rp2040-prog-reset.html -- all of these successfully reset/restart/reboot the system, but when it comes up it runs the same code it was already running, not the downloaded update.

I looked at the SFU library but its apply() method is empty (only a return statement), and the .begin() method looks like it clears/reformats the area where the download goes; I tried calling each of those (in separate trials and together) but got the same result -- the existing sketch restarted.

I feel like the part I'm missing is, having downloaded the new .bin file to flash, somehow causing it to be loaded into the working-program area where it will be executed on restart. Or perhaps I need to reconfigure things before restarting, like turning off the ethernet SPI or something? Or perhaps I'm not downloading the correct file? When I "Export Compiled Binary" I wind up with several files: .bin, .elf, .uf2, .elf.uf2, .hex, .map... I've been using the .bin version because the FileSystemStorage.h file in the CustomStorage example writes to "/ota/UPDATE.BIN", and the ArduinoIoTCloud library writes a compressed version of the .bin file. Is that the correct file to download for an update?

If it's not obvious already, all of this is pretty new terrain for me, so apologies if I'm expressing things unclearly or overlooking some obvious obstacle or solution. Thanks in advance for any assistance or clarification.

[CantStopMyBrain]

PS -- I did do this step mentioned in the README: "platform.local.txt from extras folder has to be copied into boards package installation folder. On my Ubuntu system, that meant copying from here:
~/Arduino/libraries/ArduinoOTA/extras/rp2040/platform.local.txt
to here:
~/.arduino15/packages/arduino/hardware/mbed_nano/4.1.1/
I was not 100% sure that was the correct destination folder, but there were similar files in that folder already, such as platform.txt

I also noted the instruction "For RP2040 the bundled ArduinoOTA library must be deleted" but I did not find any ArduinoOTA other than the one installed when I asked for it in the IDE.

[JAndrassy]

This ArduinoOTA library only works with the Pico Core (and the ArduinoOTA in Pico Core must be deleted).

The CustomStorage example is for the Mbed Core, which has the SFU library to boot load from file system in flash memory.
The CustomStorage example while in this library, doesn't actually use it.

[CantStopMyBrain]

Thanks for the prompt reply. Indeed the sketch I'm working on does NOT use ArduinoOTA, but it does use code from two of your examples: the download code from OTASketchDownload, and FileSystemStorage.h from CustomStorageNanoConnect. So I was hoping you had enough familiarity and knowledge that you could provide the "missing link" I seem to have: Do you know what step(s) is(are) needed to actually load the file I've saved to flash so that it replaces the current sketch and runs after restart? It would appear possible, judging from the ArduinoIoTCloud library but I seem to be missing some detail... As you say, I thought the SFU library would bootload the code from flash, but that's not happening... am I missing a call somewhere?

[JAndrassy]

does the CustomStorageNanoConnect example work for you?
do both sketches, the running and the update have the SFU?

[CantStopMyBrain]

do both sketches, the running and the update have the SFU?

BINGO!
The original update .bin I was using was just a simple blink sketch that would be easy to recognize... no SFU and no joy.
When I changed the update .bin to be a variation on the download-and-install sketch, which includes SFU, it worked!
In hindsight I can see why this matters, but it simply never occurred to me that some of the important action was going to happen after the restart. Thank you sooo much for your help! I'm going to look for your tip jar now ... ;)

[JAndrassy]

SFU checks if the sketch is larger than the SFU bin itself. a Blink sketch is smaller so it ignored it.

[CantStopMyBrain]

Oh, that's important to know... and a little surprising. So if an update results in a smaller .bin file than its predecessor, it won't be installed? It doesn't seem obvious to me that every time one updates code it's guaranteed to get larger. I wonder why it doesn't check for "is different size" rather than "is larger"?
Do you have a link to the SFU source? I'd be curious to compare with what I find in my installed SFU library. SFU.h/.cpp are mystifyingly brief -- they define empty apply() and download() methods, and a begin() method which just mounts and possibly reformats the flash block device. There's a folder of extras that look at a glance to be for a stand-alone app and don't seem to apply the size-comparison logic you describe.
I'm mostly happy to have a functioning solution, but I don't want to overlook potential pitfalls down the road so I'd like to gain a better understanding of SFU.
Thanks again!

[CantStopMyBrain]

Wait... can you clarify: is the presence of SFU in the update .bin essential or irrelevant? Was it just the increase in size which caused it to work, or the presence of SFU in the update, or both?