Changing pin behavior after boot

Issue Overview

Users have reported difficulties in changing the input/output direction of GPIO pins on the Nvidia Jetson Orin Nano Dev board after booting. The main symptoms include:

• Inability to change the pin direction or output values dynamically using the gpiod library, which was recommended as a replacement for the deprecated /sys/class/gpio method.
• Users have confirmed that while their code runs without errors, the expected changes in pin behavior are not reflected when checking with gpioinfo, which consistently shows the pins as "input."
• The issue appears to occur during experimentation with different pin configurations on custom carrier boards.

The problem’s context includes:

• Users transitioning from the Jetson Nano, where the old GPIO method was functional.
• The Jetpack version in use is 5.1.2, which may introduce specific behaviors or bugs related to GPIO handling.
• Initial troubleshooting steps involved checking system logs using dmesg, but no specific errors were noted.

This issue can significantly impact user experience by limiting the ability to control hardware configurations dynamically, which is critical for many applications relying on GPIO functionality.

Possible Causes

Several potential causes for this issue have been identified:

• Hardware Incompatibilities or Defects: Custom carrier boards may not be fully compatible with the Orin Nano’s GPIO implementation, leading to unexpected behavior.

• Software Bugs or Conflicts: There may be bugs in the Jetpack version (5.1.2) that affect GPIO functionality, particularly with gpiod.

• Configuration Errors: Incorrect configuration of the gpiod library or improper initialization of GPIO pins could lead to failure in changing pin states.

• Driver Issues: The drivers for GPIO handling might not be fully optimized or compatible with certain setups, affecting their performance.

• Environmental Factors: Power supply issues or temperature variations could potentially influence GPIO behavior.

• User Errors or Misconfigurations: Users may not be following the correct procedures for initializing and controlling GPIO pins with gpiod, especially if they are transitioning from older methods.

Troubleshooting Steps, Solutions & Fixes

To address the issue of changing pin behavior after boot on the Nvidia Jetson Orin Nano Dev board, users can follow these troubleshooting steps and solutions:

1. Verify Jetpack Version:

   • Ensure you are using Jetpack 5.1.2 as mentioned in discussions. Consider updating to a newer version if available.

2. Check Pin Configuration:

   • Use gpioinfo to list current pin configurations and ensure you are targeting the correct pins.

3. Reboot and Test gpiod:

   • After making changes to your code or configuration, reboot the device and test again. Users have reported that gpiod works correctly after a reboot.

4. Use gpiod Commands:

   • Utilize command line tools provided by gpiod to set pin directions and values. Example commands include:

     gpiod set <chip> <line>  # Set line value
     gpiod get <chip> <line>  # Get line value
     

5. Check dmesg Logs:

   • Run dmesg to check for any kernel messages related to GPIO that could indicate issues or conflicts during boot.

6. Test with Minimal Code:

   • Create a minimal example using gpiod to isolate any issues in your application code:

     #include <gpiod.h>
     
     int main() {
         struct gpiod_chip *chip;
         struct gpiod_line *line;
         int ret;
     
         chip = gpiod_chip_open_by_number(0); // Open chip
         line = gpiod_chip_get_line(chip, 4); // Get line number 4
     
         gpiod_line_request_output(line, "test", 0); // Request output
         ret = gpiod_line_set_value(line, 1); // Set high
         
         // Clean up
         gpiod_line_release(line);
         gpiod_chip_close(chip);
         return ret;
     }
     

7. Follow Best Practices:

   • Always initialize GPIO pins properly before use and ensure you are releasing resources after usage.
   • Transition fully to using gpiod instead of /sys/class/gpio as it is deprecated and unsupported.

8. Seek Community Support:

   • If issues persist, consider reaching out on forums or communities focused on Nvidia Jetson products for additional insights or shared experiences from other users.

By following these steps and utilizing recommended practices, users should be able to effectively manage GPIO pin behavior on their Nvidia Jetson Orin Nano Dev boards.