Changing DP1_AUX_P and DP1_AUX_N to Open-Drain on Nvidia Jetson Orin Nano Dev Board

Issue Overview

Users are attempting to modify the configuration of DP1_AUX_P and DP1_AUX_N pins from Bidirectional to Open-Drain on a custom board using the Nvidia Jetson Orin Nano Dev board. The issue arises when users try to make these changes in the device tree source (dtsi) file, but the modifications do not appear to take effect. This problem occurs during the hardware configuration process for a custom board design that incorporates a level shifter circuit with open-drain characteristics.

Possible Causes

1. Misunderstanding of Default Configuration: The default settings for these pins may already support the desired functionality, making manual changes unnecessary.

2. Incorrect Modification Procedure: Users might be attempting to modify the wrong file or using an incorrect method to change the pin configuration.

3. Device Tree Compilation Issues: There could be problems with the compilation or application of the modified device tree, preventing the changes from being reflected in the final dtsi file.

4. Hardware-Specific Limitations: The Jetson Orin Nano Dev board might have hardware-level restrictions that prevent certain pin configurations from being changed through software.

Troubleshooting Steps, Solutions & Fixes

1. Understand Default Configuration

   • The default setting for DP1_AUX_P and DP1_AUX_N pins already supports I2C mode, which is compatible with open-drain functionality.
   • It is generally recommended to keep the default settings for HDMI design.

2. Verify Necessity of Changes

   • Assess whether changing the pin configuration is truly necessary for your custom board design.
   • Consider consulting with Nvidia support or reviewing the Jetson Orin Nano Dev board documentation to understand the implications of modifying these pins.

3. Review Custom Board Design

   • If your custom board has already been manufactured with an open-drain level shifter circuit, evaluate whether the default I2C mode support is sufficient for your needs.

4. Explore Alternative Solutions

   • If changes are absolutely necessary, consider the following options:
     a. Investigate hardware-level modifications that can be made to your custom board to accommodate the default pin configuration.
     b. Explore software-level workarounds that can achieve the desired functionality without changing the pin configuration.

5. Consult Nvidia Developer Forums

   • If the issue persists, create a detailed post on the Nvidia Developer Forums, including:
     • Specific details about your custom board design
     • The exact steps you’ve taken to modify the dtsi file
     • Any error messages or unexpected behavior you’ve encountered

6. Best Practices

   • Always thoroughly test any modifications on a prototype or development board before finalizing your custom board design.
   • Keep detailed documentation of any changes made to the default configuration for future reference and troubleshooting.

It is worth emphasizing that based on the forum discussion, the consensus seems to be that changing these pins to Open-Drain is unnecessary, as the default configuration already supports the required functionality for most use cases, including I2C mode. If possible, it’s recommended to work with the default settings to ensure compatibility and avoid potential issues.