Put somewhere it won't be overridden by the customer flashing their own firmware.
Two options:
- Embed with linker script
- Embed with UF2
For both we have to create a build script that builds a different variant of the firmware.
The script accepts the serial number and embeds it in the image.
The regular build script that customers would use builds an image that doesn't include this section with the serial number. And it also must avoid overriding the serial number when flashing.
Linker Script
The serial number could be embedded in the executable via a linker script. QMK let's you easily use your own linker script.
@kiram9 you suggested this. How would we avoid the customer overwriting the serial number when they flash their own binary?
WIP branch: https://github.com/FrameworkComputer/qmk_firmware/commits/lotus-ld
UF2
A UF2 file is just a series of independent 512B blocks that each say which address they should be flashed to and include the data.
I think if we put a block at the end it won't interfere with the firmware. But the script must check that there is enough empty space.
We can reserve one of these blocks for the serial number. The factory build script includes this block in the UF2 file, the regular script doesn't.
This way the serial number is preserved if the customer uses the default build script that we'll upstream to QMK.
They could modify it to overwrite the entire flash.
Put somewhere it won't be overridden by the customer flashing their own firmware.
Two options:
For both we have to create a build script that builds a different variant of the firmware.
The script accepts the serial number and embeds it in the image.
The regular build script that customers would use builds an image that doesn't include this section with the serial number. And it also must avoid overriding the serial number when flashing.
Linker Script
The serial number could be embedded in the executable via a linker script. QMK let's you easily use your own linker script.
@kiram9 you suggested this. How would we avoid the customer overwriting the serial number when they flash their own binary?
WIP branch: https://github.com/FrameworkComputer/qmk_firmware/commits/lotus-ld
UF2
A UF2 file is just a series of independent 512B blocks that each say which address they should be flashed to and include the data.
I think if we put a block at the end it won't interfere with the firmware. But the script must check that there is enough empty space.
We can reserve one of these blocks for the serial number. The factory build script includes this block in the UF2 file, the regular script doesn't.
This way the serial number is preserved if the customer uses the default build script that we'll upstream to QMK.
They could modify it to overwrite the entire flash.