They say…

8.5.2 OS UPGRADE
Download the Octatrack OS file from the Elektron website.
Connect the Octatrack to a computer using a USB cable, select USB DISK MODE and press [YES] to make the Octatrack’s Compact Flash card appear as an external mass storage device in the computer.
Then place the OS file with the file extension .bin in the root (the top level of the file structure and not inside any folder) of the Compact Flash card.
Unmount the Octatrack from your computer operating system to exit USB DISK mode, select OS UPGRADE and then press [YES]. A prompt will appear asking if you want to continue with the OS upgrade. Press [YES] to upgrade the OS. Press [NO] to cancel the operation.
You can also use the MIDI UPGRADE option in the STARTUP menu to upgrade the Octatrack OS.
The active project will automatically be synced to the Compact Flash card before the OS is upgraded.

…in the manual.

1 Like