RTC Not Saving on Nvidia Jetson Orin Nano with L4T 35.4.1

Issue Overview

Users are experiencing issues with the Real-Time Clock (RTC) on the Nvidia Jetson Orin Nano Dev board running L4T version 35.4.1. The specific symptom is that after executing the command hwclock -w to write the system time to the RTC and subsequently rebooting the device, the RTC fails to retain the correct time, reverting to 1970. This issue occurs during a cold reboot, indicating that the RTC does not save time when power is completely cut off.

The problem has been consistently reported by multiple users, particularly in scenarios involving power loss. Users have confirmed that a dedicated battery is connected to the carrier board, which is essential for maintaining RTC functionality across reboots. The issue affects user experience by preventing accurate timekeeping, which can impact applications relying on time-sensitive operations.

Possible Causes

• Hardware Incompatibility or Defects: There may be issues with the RTC hardware on the Orin Nano or compatibility problems with certain carrier boards.

• Software Bugs or Conflicts: The L4T version 35.4.1 may contain bugs affecting RTC functionality, especially when compared to other versions like L4T 35.3.1.

• Configuration Errors: Incorrect configurations in the device settings or RTC setup could lead to failures in saving time.

• Driver Issues: Outdated or incompatible drivers might cause communication problems between the operating system and the RTC hardware.

• Environmental Factors: Power supply issues or fluctuations may affect the RTC’s ability to maintain time.

• User Errors or Misconfigurations: Users might not be following proper procedures for setting up or testing the RTC functionality.

Troubleshooting Steps, Solutions & Fixes

1. Verify Battery Connection:

   • Ensure that a dedicated battery is properly connected to the carrier board.
   • Check battery voltage using a multimeter; it should be around 3.0V at pin 235 (PMIC_BBAT).

2. Check RTC Functionality:

   • Use the command hwclock -w to write the current system time to the RTC.
   • After power off and cold reboot, check if the time persists using hwclock -r.

3. Test with Different L4T Versions:

   • If using L4T 35.4.1, consider upgrading to a newer version such as L4T 36.2, as suggested by users who reported success with different setups.
   • Alternatively, test with L4T 35.3.1 if available, as it was noted that RTC functionality worked with Orin NX under this version.

4. Compare with Other Modules:

   • Conduct tests using an Orin NX on the same carrier board and battery setup to confirm whether the issue is isolated to Orin Nano.
   • If possible, replicate tests on a DevKit for validation purposes.

5. Consult Documentation and Specifications:

   • Refer to relevant documentation for hardware specifications and RTC setup guidelines.
   • Download and review the Jetson Orin Nano DevKit Carrier Board Specification for insights into potential hardware limitations.

6. Monitor Voltage Levels:

   • After power off, monitor voltage levels at critical pins to ensure proper functionality of components related to RTC.

7. Seek Further Assistance:

   • If issues persist despite following these steps, consider reaching out to Nvidia support or community forums for additional troubleshooting assistance.

By following these troubleshooting steps and solutions, users can better diagnose and potentially resolve issues related to RTC functionality on their Nvidia Jetson Orin Nano Dev boards running L4T 35.4.1.