PCIe Interface Signal Routing Requirements for Nvidia Jetson Orin Nano Dev Board

Issue Overview

The discussion centers around the signal routing requirements for the PCIe interface on the Nvidia Jetson Orin Nano Dev Board, specifically referencing Table 7-10 of the Orin Nano Series Design Guide V1.3. Users are experiencing confusion regarding the necessity of certain constraints when implementing PCIe Gen3 connections.

Symptoms and Context

• Symptoms: Users are uncertain about the requirement to use micro vias or back-drilled vias, as well as the limitation of only four vias, when designing for PCIe Gen3.

• Context: This issue arises during the design phase of hardware integration, particularly when users are attempting to adhere to the guidelines provided in the design documentation.

• Specifications: The discussion references specific design guides, notably the Orin Nano Series Design Guide V1.3 and the Jetson Xavier NX Product Design Guide.

• Frequency: The issue appears to be a common point of confusion among users involved in hardware design.

• Impact: Misinterpretation of these requirements could lead to improper hardware designs that may not function optimally or at all, impacting user experience significantly.

Possible Causes

• Documentation Ambiguity: The guidelines may not clearly differentiate between requirements for PCIe Gen3 and Gen4, leading to confusion.

• Hardware Compatibility: Users may not be aware that certain constraints apply specifically to higher generations of PCIe, which could mislead them during design.

• User Misunderstanding: Lack of familiarity with PCB design practices and standards might result in incorrect assumptions about necessary routing techniques.

Troubleshooting Steps, Solutions & Fixes

Step-by-Step Troubleshooting

1. Review Documentation:

   • Revisit the Orin Nano Series Design Guide V1.3 and compare it with the Jetson Xavier NX Product Design Guide to understand differences in PCIe requirements.

2. Identify PCIe Version:

   • Confirm whether your application requires PCIe Gen3 or Gen4 by checking your project specifications.

3. Consult Additional Resources:

   • Look for community forums or Nvidia’s technical support for clarification on specific routing requirements.

Specific Commands/Procedures

• Use schematic capture software to simulate your design based on the guidelines provided.

Isolating the Issue

• Test your design with different configurations:
  • Create a simplified version of your PCB layout adhering strictly to both sets of guidelines.
  • Validate performance with both Gen3 and Gen4 configurations if possible.

Potential Fixes or Workarounds

• If you are only designing for PCIe Gen3:

  • Ignore certain constraints: It has been indicated that some constraints listed for Gen4 may not apply to Gen3, allowing for more flexibility in design.

• Recommended Approach:

  • Follow up with Nvidia support or community discussions to confirm interpretations of the guidelines before finalizing designs.

Best Practices

• Always cross-reference multiple versions of product design guides when working on hardware integration.

• Maintain open communication with other developers and engineers through forums for shared insights and experiences.

Unresolved Aspects

• The discussion remains open regarding whether all listed constraints are indeed necessary for PCIe Gen3 applications. Further investigation into Nvidia’s official stance may be required for definitive guidance.