Arduino "Cannot open DFU Error"

[NoSloppy]

@Nuur

I do have that define in my config

Well then that’s why you’re not seeing the edits you made. That define is to make the board use the presets.ini file info and ignore the uploaded config presets. see this:

OS6 & OS7 PSA - Using #define KEEP SAVEFILES WHEN PROGRAMMING

NOTE FOR ALL USERS updating to OS6 or OS7. Be sure to read the wiki page for this define before adding to your config. #define KEEP_SAVEFILES_WHEN_PROGRAMMING Once this define is added to your config, the intended use is to make all future updates to your saber via Edit Mode or ProffieOS Workbench and NOT by uploading changes to your config. This define tells the OS to use the .ini files on your SD for all presets and settings so if you have new styles, changes to fonts, colors, etc. or changes to volume, clash threshold, brightness, blade length or other settings that are editable in Edit Mode or ProffieOS Workbench that you’re trying to make via a change to your config you will not see those changes on your saber if the .ini files have different values. This can be confusing, particularly for new users, as you may have a successful upload but not see the changes on your saber. You also have to be mindful when adding, removing or updating presets in your config once this define is enabled (refer to below wiki article). I recommend only adding this define AFTER you have your saber dialed in to where you want it with all styles and settings for your “baseline” set. Then once you add this define, all future changes should only be made via Edit Mode or ProffieOS Workbench. If you need to add a style or upload other changes via your config, you should remove or comment out this define first and then only add it once you have the saber’s default set.

Understanding how the board dual boots should clarify the mode you’re in vs what you’re seeing.
The board normally boots into ProffieOS and is seen in Arduino on a COM port as “Proffieboard”. This device is a multi serial device and CDC Data is a typical way the PC sees it.
When you upload, Arduino puts the board into bootloader to send programming, then when finished, the board reboots back to ProffieOS.
If you manually force bootloader mode, then it’s already primed for programming, hence why hitting upload regardless of the board not showing on a COM port works as it does.