agx devkit uart is used by uart1, and 40-pin Expansion Header are pin 6/8/10.
uart only use when system is started, but uart is no log during system boot when power is on.
I already test cases:
1、when flash jp4.6.2, uart only use when system prompt is appeared;
2、when flash jp5.0.2, uart have few log when booting and lost most log until system is started.
what’s your actual use-case, are you going to check bootloader logs?
AGX Xavier is using combined uart, you may setup connections with port J501, a micro-USB connector which provides access to the UART console.