Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

ggabe — Tue, 12 Sep 2023 19:58:04 GMT

I wonder how much is the reasonable wear-preventing write frequency. I’m about to either add an FRAM, or use the internal flash, for an every 3 second update. (It is to store auto zero values, so that the instrument can wake up immediately, instead of running through a 1 minute warmup cycle)

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

Jan Cumps — Fri, 01 Sep 2023 07:40:34 GMT

the size of the block can be defined as a constant:

(the syntax highlighting in the script is done by a VSCode extension: LinkerScript)

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

DAB — Thu, 31 Aug 2023 19:26:18 GMT

Great idea Jan.

I hope to get my Pico set up with Labview this weekend.

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

dougw — Thu, 31 Aug 2023 17:04:42 GMT

Great blog. The idea should be useful for lots of modern MCUs, especially devices that have large FLASH onboard.

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

scottiebabe — Thu, 31 Aug 2023 12:10:52 GMT

Excellent work Jan.

Flash isn't directly CPU writeable, so perhaps you don't need the 'w' flag in you linker script. There may be a way to ensure gcc never uses that flash space so when you update your application code you don't ever over write your calibration flash page. You would initialize the calibration constants in your initialization code if the cal page isn't valid. Because flash isn't byte erasable, you could reserve 2 flash pages. Then you erase one page and scratch away until a full update a write has completed at which point you mark the page as valid or complete. So, if the application code crashes or power goes out during a cal parameter write you still have the last cal page.

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

Fred27 — Thu, 31 Aug 2023 09:56:02 GMT

A really useful write-up. Thanks.

RE: Raspberry Pico C SDK: reserve a Flash memory block for persistent storage

BigG — Wed, 30 Aug 2023 21:42:06 GMT

I haven't explored the Pico C SDK in detail, but I believe it should be possible, which is to get the Pico to emulate a USB flash memory stick. This allows you to copy a file into that flash memory location when you connect the USB cable to a computer and then use this file as part of your application.

I believe there are some Pico C USB examples available, which could be extended for this purpose - maybe this is your next challenge.

I took the other route which is to use the Arduino MbedOS core for the Pico to do similar, as shown here: [mention:a65f23551c6b4908b210adcc7eec2df1:f7d226abd59f475c9d224a79e3f0ec07]

Personally, I really like this functionality but I think it needs more work to make it more robust.