How do I boot from a USB drive (even if there is a bootable eMMC)

[radxa4chris]

Trying to replace eMMC OS

Here is the sequence: Connect all as you wish (HDMI,Keyboard,microSD 2GB) Locate the middle SMD push button on the board (positioned between the first near the USB-C connector and directly to the left of the HDMI port where two of those are located). Press and hold(!) maskrom button and connect USB-C to power on to see eventually the OS from SD card (dietPi rel. Trixie in my case) booting up. Then let go. Hardware Context: This forces the RK3399 BootROM to skip loading the bootloader …