HDMI resolution and Enterning in u-boot

[Fra]

Good morning,

I've got a Libre Computer Renegade, with Amrbian Bullseye minimal (on an sd card) . Changing HDMI monitors (of different sizes and resolutions) the board does not adjust automatically the resolution, so, sometimes the display is unreadable because written are too small, and I can't set a resolution to beng able to use it.

Surfing armbian docs, it seems to be an environment problems that could be solved by chanching u-boot parameters.

I tried to enter in u-boot command shell but I can't. Pushing backspace while it is booting make no effect (tried also with serial console but it didn't work).

How can I enter in u-boot environment to set an HDMI monitor resolution?

 

Thanks in advance