AM69 V1.0 Aquila DisplayPort AUX channel- no traffic

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DisplayPort AUX Channel Issues on Custom Aquila AM69 Carrier Board

Based on your description of the DisplayPort AUX channel not functioning on your custom carrier board while working correctly on the Aquila Development Board, here are several potential causes and debugging approaches:

Hardware Version Considerations

First, verify which version of the Aquila AM69 module you’re using(1). The V1.1A revision includes several important fixes that could affect DisplayPort functionality(1). Key hardware upgrades in V1.1A include:

  • Errata #1: Added a dedicated 25MHz crystal for the Ethernet PHY to solve clock jitter issues(1)
  • Errata #3: Series capacitors added on USB_2_SS_TX lines(1)
  • Errata #4: VBUS input voltage divider added for 5V tolerance(1)
  • Errata #5: CTRL_RESET_MICO# signal compliance fix(1)

DisplayPort Signal Requirements

According to the Aquila Carrier Board Design Guide, DisplayPort interfaces require specific signal handling(2). The MIPI DSI signals are documented with specific pin assignments(2):

MIPI DSI Signal Pins(2):

  • DSI_1_CLK_P/N (A38/A37)
  • DSI_1_D0_P/N through DSI_1_D3_P/N (A44/A43 through A32/A31)
  • Associated I2C and GPIO signals for control

Debugging Approaches

  1. Signal Integrity Verification

    • Verify that your AUX P/N differential pair routing maintains proper impedance matching
    • Check for any series capacitors or termination resistors that might be missing or incorrect
    • Ensure the AUX channel routing length matches the reference design

  2. Power Domain Analysis

    • Confirm all power domains are properly sequenced and stable
    • Verify that the DisplayPort power rails are within specification

  3. Module Version Compatibility

    • If using V1.0A modules, consider the potential impact of the hardware errata mentioned above(1)
    • The V1.1A revision addresses several signal integrity issues that could indirectly affect DisplayPort operation(1)

  4. Reference Design Comparison

    • Compare your custom carrier board schematic against the Aquila Development Board reference design
    • Pay particular attention to pull-up/pull-down resistors, termination, and signal routing

Software Considerations

The boot logs from similar DisplayPort issues show that the system attempts to read receiver capabilities and EDID data(3). The failure to read AUX address 0 with no oscilloscope activity suggests a hardware-level issue rather than a software configuration problem.

Recommended Next Steps

  1. Hardware Audit: Perform a detailed comparison of your AUX channel implementation against the Aquila Development Board V1.3A reference design(1)
  2. Module Version Check: Verify which Aquila AM69 module revision you’re using and consider the hardware errata impacts(1)
  3. Signal Integrity Testing: Use proper differential probes to verify AUX signal integrity and timing
  4. Power Analysis: Ensure all DisplayPort-related power domains are stable and within specification

The fact that the same software and module work correctly on the development board strongly suggests a hardware implementation difference on your custom carrier board.

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Toradex AI Assistant.

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