Pre-Boot Serial Console Howto ?

How to get the pre-boot serial console output ?

Connect a serial cable to your PC and use a terminal application like Minicom.

No, not what i want to know!

The serial console output is “garbled” prioir to the linux kernel booting!

I want to see the uboot process

Baud Rate: 115200
Data Bit: 8
Stop: 1
Parity: None

You will not see the u-boot due to the presets in the fastboot.bin.
So pretty much you are going to see the kernel loading up.

Thank you falco152, i tried other baud rates but can’t find out what the fastboot presets are ?

I don’t know much either.
It is cooked inside fastboot.bin

There are a few allowable settings you can modify that are handled inside ie base RFS and Kernel start address.

FYI, there is no “boot prompt” that I can tell…wish u-boot had the extensions. I do have some tegra embedded hardware I work with that has an extended u-boot in it, and allows a boot prompt, along with custom boot environment setup (e.g., telling it which boot device to use to boot to an SD card for kernel or kernel+rootfs). That environment is a big plus to development time, but does not yet exist in jetson so far as I know. Any kind of “garbage” prior to boot or during boot would almost have to come from serial port settings being wrong. I use the same settings as falco152 which work great for me with no garbage characters.