SpenceKonde
commented
1 year ago You can do so freely if using Optiboot through the Flash library.
But you're not using optiboot, so no that's not supported. The tricky part is that if you want to rewrite the app section, the code doing the write needs to be in the bootloader section, so you need a "fake" bootloader (this is what we do on DxCore - but over there the code we need to run is trivial SPM Z, RET. On these parts both the writes to the page buffer AND the command to write it must be done in a higher privileged section of mermory If I were to add a menu that changes APPEND (this in and of itself is a pain in the fucking ass, because he APPEND isn't the same in all parts so there has to be a per-chip declaration in boards.txt of what each of them someone coughyoucough would have the task of writing a flashwrite library de novo. You'd have my defines to guide you, ie you could detect how much space and what the address of the start of it was
The IDE could be made to disallow app code to go into appdata by lowering chip flash size.
Unreal-Dan
Hello @spencekonde, first thank you for all your hard work on Megatinycore!
My friend and I have been using your library quite reliably to run a firmware on an atmel attiny3217 1-series, we flash it with a separate Uno with jtag2updi.
Our only issue is we are finding that we need more than the available 255 bytes of eeprom, and we cannot fit any external memory modules onto the circuitboard.
On other devices we have that run the same firmware we just rewrite the flash memory but we seem to have hit a roadblock trying to do that with the attiny3217 and megatinycore.
I have noticed that in the boards.txt you have set the fuses for append and bootend to 0:
If I understand correctly this means the entire section of flash is 'bootloader' code and any attempt to write to a region of flash memory via the NVMCTRL will fail due to the write protections.
I really need to reserve a section of flash memory that is re-writable (at least 1 or 2 kb) and I am willing to get nitty gritty to do it. I am quite experienced and can handle complex instructions and code, in fact I will probably solve the problem eventually by wrapping my own build chain instead of arduino... But it would help greatly if you could give some insight into the issue, and/or point us in the right direction.
Would it be possible to just modify some default settings in the default linker script (is it avr1.x?) for our platform such that a separate region is created that can be written with the nvmctrl?
Thanks in advanced
Dan