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Flash Download Tool Combined BIN file erases stored NVS data

Posted: Tue Jun 16, 2026 8:14 am
by Josy_Rausch
Hello,

I am using the Flash Download Tool to flash binaries to my ESP32-C6-WROOM-1.
I store some important data (a bool and an unsigned integer value) in NVS, and this works correctly because after a power restart I can still read the saved data.

When I make changes to my program and build it, the binary files are generated.
If I flash each binary file separately (bootloader.bin, partition_table.bin, and app.bin) and then perform a power restart, the NVS data is not deleted.

However, when I combine the three binary files into one and flash this single binary file, my saved NVS data gets deleted.

I understand from the documentation that this can happen when using the “combine” option:
Screenshot 2026-06-12 105700.png
Screenshot 2026-06-12 105700.png (69.12 KiB) Viewed 71 times
I would expect, however, that flashing the three binaries separately or flashing a combined binary should behave in the same way.

Am I doing something wrong?
How can I prevent the NVS data from being erased when using the combined binary method?

Re: Flash Download Tool Combined BIN file erases stored NVS data

Posted: Tue Jun 16, 2026 11:47 pm
by Sprite
'Any unused area between firmware files will be filled with FF' - and I bet that the NVS area is somewhere between your bootloader and app. Solution, if you insist on flashing the combined binary, would be to customize your partition table so the NVS partition comes after the app partition.

Re: Flash Download Tool Combined BIN file erases stored NVS data

Posted: Mon Jun 22, 2026 9:40 am
by Josy_Rausch
'Any unused area between firmware files will be filled with FF' - and I bet that the NVS area is somewhere between your bootloader and app. Solution, if you insist on flashing the combined binary, would be to customize your partition table so the NVS partition comes after the app partition.
Alright, Thank you.