EEPROM.update is missing

[arturo182]

I have some Arduino code that I want to make work on multiple cores, including this one, the code uses EEPROM.update, but this function is not available in this core.

From my understanding EEPROM.put and EEPROM.update differ only in the way that put always writes the value to EEPROM, and update only does it if the previous value doesn't match the new one. Looking at the code for EEPROM.put in this core, that's what put it already does anyway. So I would like to propose adding an update function that just calls put, and the issue will be resolved.

I can make a PR for it, just wanted to consult first if this is the way you want it handled, or maybe you had something else in mind.

Thanks!

[earlephilhower]

@arturo182 the call was omitted on purpose. There is no real EEPROM, so it is impossible to write updates to EEPROM on byte-wide basis. Basically, the EEPROM library need to do your edits on a in-RAM copy and then erase and write a changed block to flash on EEPROM.commit().

The reason it was done this way is the flash probably has 1,000-10,000 write cycles before it fails, whereas EEPROM can probably go 100,000-1,000,000 cycles before an issue happens. So it is important to only commit() when you need to. See the examples for the proper EEPROM cycle here.

Another alternative is to drop the fake EEPROM and just use a File. We have a real filesystem with directories and wear-leveling, and you can commit partial writes (will write to a new flash block and mark old one invalid). That's a much better solution if you can put in a little work.

[arturo182]

Ah, I see, I didn't look into the implementation too much. Of course, it makes sense to not clobber the flash all the time :)

But, I'm not sure how the implementation lead to the decision to skip update, from the Arduino docs it does seem put and update perform the same operation in the same way, except for update first checking the existing value, so adding an update as an alias for put shouldn't affect or break anything except making more existing code compatible with this core.

[earlephilhower]

Fair enough. Would you like to make a new method EEPROM.update() which just calls EEPROM.put()? The user would still need to worry about the commit() addition, but there's not much that can be done about it at compile time.

[arturo182]

Yes, the user still has to call begin and commit 👍