ESP8266 Community Forum

- Sat Dec 26, 2015 8:15 am #37153

If your device has 2mb or more of flash you can just use big flash mode and you only need to link one image. Although linking two different images isn't difficult. I don't see anything else in your list of requirements that it doesn't do already.

How does it work then? Espressif isn't exactly very forthcoming with useful details (and yes, I know the OTA Flash document).

All my devices have 4 mbit flash, of which almost half is used for the image (276 kbyte netto left).

- Sat Dec 26, 2015 8:49 am #37155

How does it work then? Espressif isn't exactly very forthcoming with useful details (and yes, I know the OTA Flash document).

I'm starting to suspect you haven't read this thread or anything about rBoot. It's nothing to do with Espressif so their documentation is irrelevant. You might want to start with the rBoot readme: https://github.com/raburton/rboot/blob/ ... readme.txt

All my devices have 4 mbit flash, of which almost half is used for the image (276 kbyte netto left).

You'll struggle then, 4mbit is really too small to be useful (and below the minimum recommended flash size for the espressif sdk). However it is possible if your rom coming in at less than half the flash size (and the overheads that reduce the usable space) but you won't be able to use big flash support (as you have a very small flash) so you'll have to have separately linked roms.

- Sun Dec 27, 2015 4:55 am #37212 I did read some, but not all (yet). I am going to do that if I am sure it's going to do what I want

The "good news" is that I have some flash 32 mbit flash chips lying around (of the supposed "supported" type), which I can solder in to replace the 4 mbit flash chips. I guess this is the time to start trying the first

How long takes flashing OTA actually? I now can flash a 256kbyte image in something like 10 seconds over the UART in 1 mbaud mode. The OTA flashing should be at least as quick of course.

I guess the images for "big" rboot can only be started from rboot and cannot be flashed standalone (for users that don't have rboot installed)?

- Sun Dec 27, 2015 5:03 am #37213 Flashing takes 2 or 3 seconds, depends on the size of the rom of course.

Big flash mode allows roms to be placed beyond the first 1mb of flash, which is something that is not possible without a bootloader and altering the SDKs flash memory mapping. If a user isn't using a bootloader then they can only have one rom, which would be in the first 1mb of flash anyway, they would not need (or be able) to put the rom higher in flash.