Debug UART Repurposing on Nvidia Jetson Orin Nano 8GB

Issue Overview

Users of the Nvidia Jetson Orin Nano 8GB development board are experiencing difficulties when attempting to use the debug port as a standard UART port. Specifically, one user reported that their custom board, which uses UART2 to control an STM32 microcontroller, is not functioning as expected. This issue arises during the setup and configuration of custom hardware interfacing with the Orin Nano, potentially limiting the board’s versatility for certain applications.

Possible Causes

1. Hardware Limitation: The debug port on the Orin Nano 8GB may be designed specifically for debugging purposes and not intended for use as a standard UART port.

2. Default Configuration: The system’s default settings might prioritize the debug functionality of the port, preventing its use as a general-purpose UART.

3. Device Tree Configuration: The current device tree may not be configured to allow the debug port to function as a standard UART port.

4. Driver Issues: The appropriate drivers for using the debug port as a standard UART may not be loaded or configured correctly.

Troubleshooting Steps, Solutions & Fixes

1. Use UART1 Instead

   • As a primary solution, use UART1 (/dev/ttyTHS0) for communication with the MCU.
   • This port has been confirmed to work correctly for standard UART communication.

2. Repurpose Debug UART
   If you specifically need to use the debug port as a standard UART, follow these steps:

   a. Disable the combined UART functionality
   b. Enable the port as a normal UART

   This process involves modifying the device tree and related files. Here’s a general outline:

   • Locate the device tree file for your Orin Nano board.
   • Find the section related to the debug UART.
   • Modify the configuration to disable the combined UART functionality.
   • Add or modify entries to enable the port as a standard UART.
   • Recompile the device tree and flash it to your board.

   Note: This method has not been officially verified by Nvidia, and they cannot guarantee performance in this use case.

3. Refer to External Resources
   For detailed instructions on repurposing the debug UART, refer to the following thread:
   "Repurpose Debug UART for ‘normal’ comms on Xavier NX – #6 by JerryChang 23"

4. Consult Nvidia Documentation
   Review the official Nvidia Jetson documentation for any updates or specific instructions related to UART configuration on the Orin Nano 8GB.

5. Community Support
   If the issue persists, consider reaching out to the Nvidia Jetson developer community forums for additional assistance or to share your findings if you successfully repurpose the debug UART.

Warning: Modifying the device tree and system configuration can potentially affect system stability. Proceed with caution and ensure you have a backup of your current configuration before making changes.