HDMI_CEC and SLEEP/WAKE* Pin Voltage Discrepancies on Nvidia Jetson Orin Nano Dev Board

Issue Overview

Users have reported confusion regarding the voltage specifications and pull-up resistor configurations for two specific pins on the Nvidia Jetson Orin Nano Developer Board:

1. Pin 177 (HDMI_CEC): Discrepancy between the pin description document and the schematic regarding the pull-up resistor value and voltage.
2. Pin 250 (SLEEP/WAKE*): Inconsistencies in the pin type, pull-up resistor value, and voltage across different documentation sources.

These discrepancies have led to uncertainty about the correct specifications and proper usage of these pins, potentially affecting hardware design and integration efforts.

Possible Causes

1. Documentation Inconsistencies: The discrepancies may be due to outdated or conflicting information in different documentation sources, such as the pin description spreadsheet and the schematic.

2. Design Changes: The specifications might have changed during the development process, and not all documentation was updated to reflect these changes.

3. Context-Dependent Configurations: The pin configurations may vary depending on the specific module or carrier board being used, leading to apparent contradictions in the documentation.

4. Misinterpretation of Technical Specifications: The complexity of the pin configurations, especially for multi-purpose pins, may have led to misunderstandings or incomplete descriptions in the documentation.

Troubleshooting Steps, Solutions & Fixes

To address the confusion and provide clarity on the correct pin specifications, follow these steps:

For Pin 177 (HDMI_CEC):

1. Understand the Correct Configuration:

   • The HDMI_CEC pin is a 1.8V open-drain (OD) pin that is 3.3V tolerant.
   • The pull-up resistor on the module is not mounted.

2. Reconcile Documentation:

   • Update the pin description document to reflect that the 10kΩ pull-up to 1.8V is not actually mounted on the module.
   • Confirm that the schematic (P3768_A04) showing a 162kΩ 1% pull-up to VDD_3V3_HDMI is correct for the carrier board.

3. Design Considerations:

   • When designing hardware that interfaces with this pin, consider that there is no on-module pull-up.
   • If a pull-up is required for your application, implement it externally according to your specific needs.

For Pin 250 (SLEEP/WAKE*):

1. Clarify the Pin Configuration:

   • The SLEEP/WAKE* pin is pulled up to 5V on the carrier board.
   • On the module, it is routed to a SoC pin through a diode and then pulled up to 1.8V.

2. Update Documentation:

   • Revise the pin description document to accurately reflect the dual pull-up configuration:
     • 10kΩ pull-up to VDD_5V_SYS on the carrier board
     • 100kΩ pull-up to 1.8V on the module (after the diode)

3. Explain the CMOS-5V Designation:

   • The pin type "CMOS-5V" likely refers to its compatibility with 5V logic levels on the carrier board side.
   • Clarify in the documentation that while the pin can handle 5V input, it operates at 1.8V internally on the module.

4. Usage Guidelines:

   • When interfacing with this pin, be aware of the voltage level translation occurring between the carrier board (5V) and the module (1.8V).
   • Ensure that any external circuitry connected to this pin is compatible with both voltage levels.

General Recommendations:

1. Consult Official Documentation:

   • Always refer to the most recent official Nvidia documentation for the latest and most accurate information.
   • Check for any errata or updates that may have been released to address documentation discrepancies.

2. Verify with Hardware Testing:

   • If possible, use a multimeter or oscilloscope to measure the actual voltage levels and verify the presence of pull-up resistors on your specific board.

3. Seek Official Clarification:

   • For critical designs or if any doubt remains, contact Nvidia support or use official forums to request clarification directly from the development team.

4. Document Findings:

   • Keep a record of any clarifications or corrections you receive regarding pin specifications for future reference and to share with the community.

By following these steps and recommendations, users can ensure they have the correct information for proper hardware design and integration with the Nvidia Jetson Orin Nano Developer Board.