Debug UART (Internal Use Only)

We didn’t enable the debug UART in the mass production version. However, if our partners need to use the debug UART to port a custom OS or special driver, please refer to the following steps and proceed with caution.

The position of Debug UART

The relevant debug UART pins are located at Pin 12 (UART_TX), Pin 13 (UART_RX), and Pin 25 (UART_GND).

A special GPIO to enable Debug UART

The onboard UART/COM ports are controlled by a GPIO to prevent unwanted or dirty characters during the boot-up sequence. By default, E10 (GPIO12/PAC.07) is enabled only after the system boots into the OS. If you want to enable the debug UART immediately after the Jetson is powered on, you will need to configure gpio using the pinmux.

This involves modifying the relevant files and reflashing the Jetson module after applying the pinmux changes. We assume that you have already created an L4T folder with the NRU tarball extracted.

File name: L4T/bootloader/Orin-nru220-gpio-default.dtsi

gpio_main_default: default {

 gpio-output-low = <
     ...
-    TEGRA234_MAIN_GPIO(AC, 7) /* for Debug UART */
     ...
 >;
 
 gpio-output-high = <
     ...
+    TEGRA234_MAIN_GPIO(AC, 7) /* for Debug UART */
     ...
 >;

};