[Jetson TK1] Interrupting and debugging U-Boot

I’ve flashed my Jetson with U-Boot.
In the “Tegra Linux Driver Packag Documents R19.3” it says in “Debugging U-Boot Environment > Interrupting U-Boot” section that to debug U-Boot environment one can interrupt U-Boot by pressing any key at boot time:

However, I haven’t been able to successfully interrupt the boot.
Can anyone help me?

You must use the serial console to do this. The time to interrupt is very fast. If you interrupt immediately, you enter the u-boot command line. About 1 or 2 seconds after this time is gone, it enters the kernel selection menu, and again you have about 1 or 2 seconds to interrupt. Should you just want to continue after hitting the u-boot command line, the command “boot” will continue on.

Were you using the serial console?

No, I were not :)
Thanks for the info!

Just to make sure: this is the serial port that is the DB9 connector and to which all the boot time messages are logged (including from the boot loaders), right? I’ve tried typing like mad right out of power up and haven’t managed to get it to interrupt the boot.

This is indeed the DB9 serial port; however…

The default bootloader is fastboot.bin, not u-boot.bin. So unless you flashed bootloader while specifically specifying to use u-boot, there is no interrupt…fastboot.bin is as fast (and dumb) as possible.

Ah, then I guess it’s good I’m building the TK1 u-boot in another window. Thanks!