I’ve been having trouble getting to the u-boot monitor on the TX2i. I attempted the following 2 methods of key-presses (both upon powering the TX2i off/on again, and upon issuing the reboot command to terminal):
Connecting a physical keyboard to the USB
Connecting a TX2 to serial (J17) and sending bytes via minicom to the TX2i.
Neither of these methods worked. What is more worrying is that I never saw any U-Boot-specific messages when booting up (I am assuming there should be a message that says “press any key to interrupt U-Boot”).