TX Pin Not Working on Jetson Orin Nano with Flight Controller

Issue Overview

Users are experiencing issues with the TX pin on the Nvidia Jetson Orin Nano when attempting to establish a serial connection with a flight controller (Cube Orange +). While the RX pin is successfully receiving signals (e.g., heartbeat from the flight controller), the TX pin does not appear to send any data back to the flight controller. This issue arises during setup and integration of the Jetson Nano with external hardware.

Specific Symptoms

• The command mavproxy.py --master=/dev/ttyTHS0 runs without errors, but no data is sent from the Jetson to the flight controller.
• Successful reception of signals via RX, indicating that the connection is established.
• Users report that they have completed a UART loopback test successfully, confirming that the TX pin can send data locally.

Context

The problem occurs during the integration of a 5G modem and flight controller with the Jetson Orin Nano. Users are trying to configure serial communication for autonomous vehicle applications, which requires reliable data transmission between devices.

Hardware/Software Specifications

• Hardware: Nvidia Jetson Orin Nano, Cube Orange + flight controller
• Software: JetPack 5.3, MAVProxy

Frequency of Issue

This issue appears to be relatively common among users working with serial communication on the Jetson platform, particularly when integrating with flight controllers or similar devices.

Impact on User Experience

The inability to send data from the Jetson to the flight controller can severely limit functionality and hinder project development, particularly in autonomous systems where communication is critical.

Possible Causes

1. Signal Level Mismatch: The logic levels between the Jetson’s TX pin and the flight controller’s RX pin may not match.

   • Explanation: If one device operates at a different voltage level (e.g., 3.3V vs. 5V), it could prevent successful data transmission.

2. Flow Control Issues: The flight controller may require specific flow control settings that are not configured correctly.

   • Explanation: If RTS/CTS flow control is expected but not set up, it could lead to communication failures.

3. Driver or Configuration Errors: The Jetson’s serial driver may not be configured correctly for the specific UART being used.

   • Explanation: Incorrect settings in the device tree or driver configuration can lead to issues with data transmission.

4. Faulty Connections or Wiring: Physical connections between devices may be faulty or improperly wired.

   • Explanation: Loose connections or incorrect wiring can disrupt communication between devices.

Troubleshooting Steps, Solutions & Fixes

1. Check Logic Levels:

   • Use a multimeter or logic analyzer to verify that both devices operate at compatible voltage levels (e.g., both at 3.3V).

2. Perform a UART Loopback Test:

   • Confirm that the TX pin can send data by connecting it directly to the RX pin and checking if sent characters are received correctly:

     echo "Test" > /dev/ttyTHS0
     cat /dev/ttyTHS0
     

3. Verify Flow Control Settings:

   • Check if your flight controller requires flow control and ensure it is configured correctly in your software settings.

4. Inspect Wiring and Connections:

   • Double-check all connections between the Jetson and flight controller for any loose or incorrectly wired pins.

5. Review Device Tree Configuration:

   • Ensure that your device tree includes proper configurations for UART settings:

     dtc -I fs /sys/firmware/devicetree/base > device_tree.txt
     

6. Check for Driver Availability:

   • Verify that all necessary drivers are loaded and available for the UART interface being used:

     ls /dev/ttyTHS*
     

7. Consult Documentation:

   • Refer to Nvidia’s official documentation regarding serial communication and supported configurations for your specific hardware setup.

8. Engage Community Support:

   • Post detailed queries on forums such as Nvidia Developer Forums or Stack Overflow where other developers may have encountered similar issues.

9. Monitor System Logs:

   • Check system logs for any additional error messages that could provide more context about what is failing during execution:

     dmesg | grep tty
     

10. Unresolved Aspects:

    • Further investigation may be needed regarding specific compatibility issues between different UART configurations and connected devices.
    • Users should continue sharing their experiences in forums to build a collective understanding of these issues.

By following these troubleshooting steps, users should be able to effectively diagnose and resolve issues related to TX pin functionality on their Nvidia Jetson Orin Nano devices when connecting to a flight controller.