Jetson Orin Nano: Issues with Serial Connection and GPIO Configuration

Issue Overview

Users are experiencing difficulties when attempting to establish a serial connection between the Jetson Orin Nano Developer Kit and external devices, such as flight controllers. The primary symptoms include the inability to send or receive data through the serial interface, specifically when using the /dev/ttyTHS0 port. Users report that while they can successfully run loopback tests, the actual communication with external devices fails, leading to confusion about the configuration and compatibility of the Jetson Orin Nano’s serial interface.

Relevant Hardware and Software Specifications

• Device: Jetson Orin Nano Developer Kit (8GB)
• Connection Method: Serial connection via /dev/ttyTHS0
• JetPack Version: 5.3 (as indicated in the discussion)

Symptoms

• The TX pin on the Jetson Orin Nano is not sending any data to the connected flight controller.
• Successful loopback tests indicate that the serial interface is functioning, but no data is transmitted to external devices.
• Users see no output or response from the flight controller when sending commands.

Possible Causes

1. Logic Level Mismatch: The voltage levels between the Jetson’s TX pin and the flight controller’s RX pin may not match, causing communication failures.
2. Flow Control Issues: The UART configuration may require flow control (RTS/CTS) that is not being utilized, leading to dropped signals.
3. Driver or Kernel Configuration Errors: There may be issues with how the device tree is configured for UART communication, which could affect pin assignments or functionality.
4. Hardware Connection Problems: Physical issues with connections or cables may prevent proper communication between the Jetson board and external devices.

Troubleshooting Steps, Solutions & Fixes

Step-by-Step Instructions

1. Check Logic Levels:

   • Verify that both devices (Jetson and flight controller) operate at compatible logic levels (typically 3.3V). Adjust pull-up or pull-down resistors as necessary.

2. Inspect Flow Control Settings:

   • Confirm whether flow control is required by the flight controller. If so, ensure that RTS/CTS lines are correctly wired and configured in your application.

3. Review Device Tree Configuration:

   • Check your device tree settings to ensure that UART settings are correctly defined for /dev/ttyTHS0. You can dump the current device tree with:

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

4. Run Loopback Test:

   • Perform a loopback test by shorting TX and RX pins on the Jetson board and sending data through a terminal program to confirm that data is sent and received correctly.

5. Check dmesg Logs:

   • Use dmesg to check for any errors related to serial communication:

     sudo dmesg | grep tty
     

6. Test with Different USB-UART Adapters:

   • If possible, test with a USB-UART adapter to see if it can communicate successfully with the flight controller.

7. Consult Documentation and Community Resources:

   • Refer to NVIDIA’s official documentation for guidance on configuring UART devices and troubleshooting common issues.

8. Update JetPack Version:

   • Consider upgrading to a newer version of JetPack if available, as updates may include fixes for known issues.

Recommended Fixes

• Users have found success by ensuring proper logic level matching between devices and verifying physical connections.
• Adjusting flow control settings has also resolved similar issues in other setups.

Best Practices for Future Prevention

• Document all configurations and changes made during development for future reference.
• Regularly check NVIDIA forums and documentation for updates regarding known issues with specific JetPack versions.

Unresolved Aspects and Further Investigation

• Users continue to seek clarity on whether specific configurations can be reliably used across different generations of Jetson hardware.
• There may be additional debugging steps required that are not fully documented in existing resources.

By following these troubleshooting steps and solutions, users can effectively address issues related to serial connection failures on their Jetson Orin Nano platform while ensuring compatibility with their hardware setups.