Circle based instruments - USB boot supported?

[my03max]

Terribly sorry if this is kind of off topic.

After building a miniDexed/dreamDexed 19-inch rack based on the rPI5 (with LCD, buttons, the rotary push encoder, etc) i had this idea that i could boot it via USB (as it would be easier to just remove the thumb-drive from the front and replace it with another thumb-drive/synth-engine and reboot).

But after a lot of trial and error, altering boot-order via eeprom (and hooking things up to HDMI for verification), it see that even if i have USB as first in line for booting (and a properly setup usb-stick with MB synths on them), it will never try to start the USB at all.

I got some advice that i should put some key files on the SD (e.g "performance" folder with files) in order for the device to "try" and then fail-over to USB, but that did not work either.

Over HDMI, i can clearly see that both SD and USB are detected. Its just that USB is never attempted to boot from by the rPI in this case. However, as soon as i plug in an SD-card, it boots up immediately.

Idk if this is a Circle issue or more a BM engine issue (that bases themselves on Circle) but i would love some guidance/input on this. Would it be possible to prioritize the boot-order defined in the eeprom and use that as-is?

[rsta2]

I tried USB boot on a RPi 5 earlier, and it worked. The necessary configuration of the bootloader is described here. This is not special to Circle and there is no special support for USB boot in it.