Orin Nano SPI3 Not Working as Expected

Issue Overview

Users have reported issues with the SPI3 interface on the Nvidia Jetson Orin Nano Developer Kit. The primary symptoms include:

• Incorrect Data Transmission: When running the spidev_test code with loopback for SPI3.0 (/dev/spidev2.0), the transmitted data does not match the expected output.
• Signal Integrity: A logic analyzer shows data on MISO and MOSI lines, and SCK and CS signals toggle correctly, but the received data is incorrect.
• Configuration Concerns: Users noted an unusual configuration in the device tree file (tegra234-p3767-0000-common-hdr40.dtsi), where all SPI3 pins have nvidia,enable-input = <TEGRA_PIN_ENABLE>;, which may not be appropriate.

The issue seems to occur consistently during testing, impacting users’ ability to interface with devices like IMUs (Inertial Measurement Units). The problem persists despite attempts to verify configurations and test different hardware setups.

Possible Causes

Several potential causes for the observed issues have been identified:

• Hardware Incompatibility: The use of longer header cables (20 cm) may affect signal integrity, leading to incorrect data transmission.
• Driver Issues: Potential misconfigurations in driver settings or SPI modes could result in improper signal handling.
• Configuration Errors: Incorrect pin muxing or device tree settings could prevent proper communication over the SPI interface.
• Environmental Factors: Signal degradation over longer cable lengths might require adjustments to drive strength.
• User Errors: Misconnections or incorrect setup procedures may contribute to the malfunction.

Troubleshooting Steps, Solutions & Fixes

Here are detailed troubleshooting steps and potential solutions to resolve the SPI3 issues:

1. Verify Jetpack Version:

   • Ensure you are using a compatible version of Jetpack (e.g., L4T 35.4.1, JetPack 5.1.2).

2. Check Hardware Connections:

   • Use shorter header cables (approximately 10 cm) for better signal integrity.
   • Confirm that MISO, MOSI, SCK, and CS connections are correct.

3. Run Loopback Test:

   • Execute the following command to test SPI communication:

     ./spidev_test -D /dev/spidev0.0 -v -p "Hello World"
     

   • Check if the received data matches the transmitted data.

4. Analyze Signal Waveforms:

   • Use a logic analyzer to capture waveforms for MISO, MOSI, SCK, and CS during both loopback tests and IMU communication attempts.
   • Compare waveforms to identify discrepancies in signal levels.

5. Adjust Drive Strength Settings:

   • If issues persist, consider adjusting signal drive strength settings in your configuration files or through device tree settings.

6. Review Device Tree Configuration:

   • Investigate the tegra234-p3767-0000-common-hdr40.dtsi file for potential misconfigurations related to SPI3 pins.
   • Ensure that necessary settings such as nvidia,enable-input are correctly configured.

7. Test with Different SPI Interfaces:

   • Attempt to use spidev1.0 (/dev/spidev0.0) as an alternative to determine if the issue is isolated to SPI3.

8. Check for Driver Errors:

   • Review system logs using dmesg for any error messages related to SPI or IMU drivers.

9. Documentation and Updates:

   • Refer to Nvidia’s official documentation for any updates related to driver or firmware that might resolve known issues.
   • Keep an eye on community forums for shared solutions or similar experiences from other users.

10. Best Practices for Future Prevention:

    • Always ensure proper cable lengths and connections when setting up hardware interfaces.
    • Regularly check for updates in firmware and software that could affect hardware performance.

By following these steps, users should be able to diagnose and potentially resolve issues with the SPI3 interface on their Nvidia Jetson Orin Nano Developer Kit. If problems persist after trying these solutions, further investigation into specific hardware components or reaching out to Nvidia support may be necessary.