Add persistent storage using part of MCUs flash

[thwr]

nanoFramework area:
General feature for most targets

Is your feature request related to a problem? Please describe.

Yes and no: Currently there is no way to save configuration parameters across restarts.

Describe the solution you'd like

In embedded projects, you often need to store a very small but configurable set of configuration parameters. The configuration can be done via a UI (Display + Keys), via a network interface (REST API, ...) or even by using desired properties of Azure IoT Hub DeviceTwin, for example.

Regardless of how the configuration is done, there should be a way to have it persist between power loss / reboot events.

To achieve this goal, nanoFramework could provide frontend applications with memory backed up by a small portion of the respective MCU's flash memory (in the range of a few kilobytes). This memory does not need to be managed in any way, frontend applications could use (binary) serialization/deserialization to store and retrieve data, for example.

Describe alternatives you've considered

External memory such as I2C/SPI EEPROMs, SD cards, etc. could suffice for this task, but require additional hardware, drivers, and application logic. On the other hand, nanoFramework already uses a system like the one described above to store network configuration parameters and certificates, so it should not be too complicated.

Additional context

This feature should be beneficial for almost all projects that go beyond "hello world". So it would be nice to see this feature becoming reality.

Submit a PR with the implementation

n/a

[networkfusion]

@thwr Is there any reason why SPIFFS is not appropriate?

[gligorov]

Looking at this, would be a nice feature to have no matter how minimal of flash. For example, I am tinkering on the TI CC1352 boards, and would be nice have few bytes even, as I need to store radio address for example which is 1 byte for RX and 1 byte for TX, so having even few bytes to store will be helpful on that target.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[thwr]

SPIFFS

Oh my... missed this one, sorry

Yes, because that requires an external IC that might not be available on off-the-shelve hardware. Already mentioned that in my initial feature request

[alberk8]

SPIFFS

Oh my... missed this one, sorry

Yes, because that requires an external IC that might not be available on off-the-shelve hardware. Already mentioned that in my initial feature request

Yes, there is internal spiff storage in the ESP32 platform. Sample here, the I: drive is the internal storage.

[thwr]

Perfectly possible, but isn't your approach platform specific?

[alberk8]

Not every platform support partitioning of the flash as flexible and with large space as ESP32.

[thwr]

Yeah, I wouldn't like to go down any kind of religious path here: Every MCU has it's own pro and con's. For example, for my needs, anything ESP-like (even the current generation) would be a poor choice.

Anyway, my suggested approach is platform independent. I would rather like to see that supported. Especially because it's already implemented for the networking configuration stuff which should be relatively easy to build upon.