Avrdude WARNING on "burn bootloader" with pio standard setting

Hi, just used a more or less blank platformio.ini to re-burn the stock bootloader to my Arduino nano.
This worked fine, also fuse settings look good, BUT when setting the lock fuses, I got the following warning:

Maybe the standard lock fuse setting should be modified to mitigate the warning and possibly future errors. Should I create an issue already or could somebody reproduce?

If you add

board_bootloader.lock_bits = 0xCF

to the platformio.ini the error is gone, yeah?

Then it’s that code that’s wrong

and it should be raised as an issue there.

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Shouldn’t it be 0xFF as no lock bit is used as per here? I’ll try both and let you know once I did it.
Ah, my Original Arduino boards.txt says you’re right :wink:

Well, the answer is - partially. What I found out:

  1. both lock and unlock bits currently are deprecated, so the warning only goes away if I modify both.
  2. Too keep the same behavior as specified in the boards.txt, I have to have a look in the datasheet and boards.txt

Original from boards.txt:

Error message says that unused bytes have to be written to 1.
According to datasheet, unused bits are (the same for lock and unlock bit mask):

So, I add 12 to the first nibble and yield:

board_bootloader.unlock_bits = 0xEF
board_bootloader.lock_bits = 0xCF


Warning gone. All fine. Will raise an issue.

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