How to reliably save data using pstorage?

RE: How to reliably save data using pstorage?

Stefan Birnir Sverrisson — Mon, 21 Sep 2015 12:06:14 GMT

Thank you Chris. I will report this for improvement in the documentation

RE: How to reliably save data using pstorage?

Chris — Mon, 21 Sep 2015 10:18:01 GMT

developer.nordicsemi.com/.../a00140.html

At the very bottom, first bullet under 'Clear'.

RE: How to reliably save data using pstorage?

Stefan Birnir Sverrisson — Mon, 21 Sep 2015 10:06:19 GMT

@Chris Where do you find this text exactly?

RE: How to reliably save data using pstorage?

Chris — Sat, 19 Sep 2015 22:22:45 GMT

Nevermind, it works as I expected and only clears one page. Makes sense since the swap is only one page. One of the rare cases where you don't take the documentation literally.

RE: How to reliably save data using pstorage?

Chris — Sat, 19 Sep 2015 21:09:32 GMT

If an 'application' requests 16 128-byte blocks, it will get 2 pages. The documentations says, "Clear operation results in clearing all storage blocks allocated to the application." Does that mean that a clear will really erase both pages even if I do pstorage_clear(&base_handle, 1024). I hope that is not the case and that it will only clear page one. And that pstorage_clear(&block8_handle, 1024) would then only clear page two. Is this how it works?

RE: How to reliably save data using pstorage?

Stefan Birnir Sverrisson — Wed, 16 Sep 2015 12:30:21 GMT

Hi Marius

Thank you for your message.

I think you are correct in all your assumptions. The pstorage module is currently not designed to reliably handle sudden power cuts during pstorage operation. We have recommended so far that when i.e. battery is close to empty that you shut down gracefully before the supply voltage drops below 1.8V, so that ongoing flash operations will be completed.

No, you are correct, there is no mechanism available from Nordic that handles the limited erase/write cycles allowed. If you write/erase the same page/pages very often, then you would need to implement a mechanism to spread the write/erase cycles on multiple pages.

I think your thread is a good summary of improvement suggestions for the pstorage module. I will report this as such.