Jetson Orin Nano Serial Port Configuration for Raspberry Pi Build HAT

Issue Overview

Users are experiencing difficulties accessing the /dev/serial0 port on the Nvidia Jetson Orin Nano when attempting to connect and use a Raspberry Pi Build HAT. The specific error encountered is a "FileNotFoundError" indicating that the /dev/serial0 device does not exist. This issue prevents users from utilizing the Build HAT’s functionality, particularly when trying to interface with sensors like the ForceSensor. The problem occurs on a clean system running Jetpack 5.1 with Python 3.8.10.

Possible Causes

1. Missing serial port configuration: The /dev/serial0 port may not be properly configured or enabled in the Jetson Orin Nano’s device tree.

2. Incompatible hardware interface: The Raspberry Pi Build HAT may be expecting a specific serial interface that is not present or configured on the Jetson Orin Nano.

3. Software library incompatibility: The buildhat Python library may be designed specifically for Raspberry Pi hardware and not compatible with the Jetson Orin Nano’s architecture.

4. Incorrect pin mapping: The GPIO pins used for serial communication on the Jetson Orin Nano may differ from those on a Raspberry Pi, causing connection issues.

5. Kernel module issues: Required kernel modules for serial communication may not be loaded or properly configured.

Troubleshooting Steps, Solutions & Fixes

1. Verify Jetpack version:
   Confirm that you are running the latest Jetpack version by checking the contents of /etc/nv_tegra_release:

   cat /etc/nv_tegra_release
   

   If not using the latest version, consider upgrading to Jetpack 5.1.1 (R35.3.1).

2. Identify available serial ports:
   List the available serial ports on your Jetson Orin Nano:

   ls -l /dev/tty*
   

   Look for entries like ttyTHS0, ttyTHS3, or ttyTHS4, which are UART ports on the Jetson Orin Nano.

3. Configure serial port in device tree:
   Edit the device tree to enable the desired serial port. This typically involves modifying files in /etc/nvidia/dtb/.
   Consult the Jetson Orin Nano documentation for specific instructions on enabling UART ports.

4. Disable console on serial port:
   If the serial port is being used for console output, disable it:

   sudo systemctl stop nvgetty
   sudo systemctl disable nvgetty
   

5. Update udev rules:
   Trigger udev to apply any changes:

   sudo udevadm trigger
   

6. Identify correct serial device:
   Instead of using /dev/serial0, try using the actual device name (e.g., /dev/ttyTHS0) in your Python code.

7. Modify buildhat library:
   If possible, modify the buildhat library to use the correct serial port for the Jetson Orin Nano. This may involve changing the default port in the library’s source code.

8. GPIO pin mapping:
   Compare the GPIO pin layout of the Raspberry Pi with the Jetson Orin Nano. You may need to create a custom adapter or modify connections to match the correct pins for serial communication.

9. Check kernel modules:
   Ensure that necessary kernel modules for serial communication are loaded:

   lsmod | grep serial
   

   If required modules are missing, load them using modprobe.

10. Serial port permissions:
    Ensure your user has the correct permissions to access the serial port:

    sudo usermod -a -G dialout $USER
    

    Log out and log back in for the changes to take effect.

11. Custom serial port configuration:
    If the Build HAT requires a specific serial port configuration, you may need to create a custom device tree overlay or modify the existing configuration to match the required settings.

12. Alternative communication method:
    Consider using an alternative communication method supported by both the Jetson Orin Nano and the Build HAT, such as I2C or SPI, if serial communication proves too challenging to implement.

If these steps do not resolve the issue, further investigation into the specific requirements of the Build HAT and its compatibility with non-Raspberry Pi hardware may be necessary. Additionally, reaching out to the Build HAT manufacturer for guidance on using their product with Jetson hardware could provide valuable insights.