MDI Interface Signal Routing Requirements for Nvidia Jetson Orin Nano Dev Board
Issue Overview
The discussion revolves around the signal routing requirements for the MDI (Media Dependent Interface) Ethernet signals on the Nvidia Jetson Orin Nano Dev Board, specifically addressing concerns about inter-pair skew as outlined in the design guide (Version 1.3). Users are experiencing confusion regarding the recommended inter-pair skew of 0.22mm for MDI Ethernet signal routes.
Symptoms and Context:
- Users are uncertain whether the 0.22mm length matching applies strictly between adjacent pairs, such as MDI_0_P/N and MDI_1_P/N.
- There is a reference to propagation delay limits, suggesting that while precise length matching may not be necessary, it could still be important for maintaining signal integrity.
- The issue arises during the design phase when users are preparing their PCB layouts based on the design guide specifications.
Frequency and Impact:
- The issue appears to be common among users designing PCBs for the Orin Nano, indicating a need for clarity in the design guidelines.
- Misinterpretation of these requirements can lead to potential performance issues in Ethernet communication, affecting overall system functionality.
Possible Causes
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Misinterpretation of Design Guidelines: Users may misunderstand the requirements for inter-pair skew, leading to incorrect PCB designs.
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Inadequate Documentation: If the design guide does not clearly explain the implications of inter-pair skew, users may struggle to apply it correctly.
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Hardware Limitations: Some users may not have access to precise measurement tools or techniques needed to achieve the recommended skew.
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Signal Integrity Issues: Failure to adhere to recommended routing practices can result in degraded signal quality and increased error rates in data transmission.
Troubleshooting Steps, Solutions & Fixes
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Review Design Guidelines:
- Thoroughly read through Table 8-2 of the Orin Nano Series Design Guide V1.3 to understand the context of inter-pair skew requirements.
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Clarify Length Matching Requirements:
- Confirm whether the 0.22mm skew applies strictly between adjacent pairs or if it is a general recommendation for all pairs. This can often be clarified by contacting Nvidia support or referring to additional documentation.
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Measure Existing Designs:
- Use precision measuring tools to assess current PCB designs for compliance with skew recommendations.
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Test Signal Integrity:
- Implement test setups to evaluate signal integrity under various configurations. This can include using an oscilloscope to measure propagation delays and ensuring they remain within acceptable limits.
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Adjust PCB Layouts:
- If skew issues are identified, adjust PCB layouts accordingly to meet the 0.22mm requirement where applicable.
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Consult with Peers:
- Engage with other developers or engineers who have successfully implemented designs based on the Orin Nano guidelines for shared insights and experiences.
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Documentation Updates:
- Suggest improvements or clarifications for future versions of the design guide based on user feedback regarding ambiguities in current documentation.
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Firmware and Driver Updates:
- Ensure that all firmware and driver updates related to Ethernet functionality are applied, as these can sometimes mitigate issues related to signal integrity.
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Best Practices:
- Follow best practices in PCB design such as minimizing trace lengths, using proper grounding techniques, and avoiding sharp angles in trace routing to enhance overall signal quality.
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Further Investigation:
- If issues persist after following these steps, consider reaching out to Nvidia’s technical support for advanced troubleshooting related to specific hardware configurations or software environments.
By adhering to these troubleshooting steps and solutions, users can better navigate the complexities of MDI interface signal routing on the Nvidia Jetson Orin Nano Dev Board and ensure optimal performance in their applications.