AM69 boot failure, stuck in Uboot

Technical Support
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1

We have a custom carrier board that connects to an adapter board where the following interfaces are wired

SPI1

SPI2

ADC1-4 (all 4 tied to GND)

QSPI (wired but not connected to anything)

OSPI (wired but not connected to anything)

I2C_6
I2C_3

Displayport (and associated GPIO)

I2S1 (not connected)

I2S2 (not connected)

DSI1 (not connected)

DSI2 (not connected)

When the adapter board is plugged in the AM69 does not boot. removing the adapter board, allowing the AM69 to boot then hotplugging it after boot everything works as expected.

We are currently unsure if Uboot is starting or if the issue occurs before this.

Can you recommend anything that might cause a boot failure? For boot we normally boot from onboard eMMC but there is also a valid SD card.

When boot fails we see

-Ethernet does not go active

-FAN controller is not active (fan does not change speed as it does on a normal boot)

The AM69 version we have is V1.0

2

Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

I’d be happy to help troubleshoot your AM69 boot issue with the custom adapter board! To provide the most accurate guidance, could you let me know which OS and version you’re running on your AM69 module?

You can get this information by running the tdx-info command on your device when it’s booted normally (without the adapter board). For more details about this command, see: Getting Device Information with Tdx-Info | Toradex Developer Center

Initial Analysis

Based on your description, this appears to be a hardware-related boot failure that occurs before the main OS loads, given that:

  • Ethernet doesn’t activate (1)
  • Fan controller remains inactive (1)
  • The system works fine when the adapter is hot-plugged after boot

Potential Causes to Investigate

Power and Reset Issues

  • RESET_MICO# signal: Ensure your adapter board isn’t holding the reset line low (1)
  • PMIC signals: Monitor PMIC_EN and PMIC_IRQ signals to verify proper power sequencing (1)
  • Power rail loading: The additional circuitry on your adapter may be overloading power rails

Signal Integrity Problems

  • Boot mode pins: Check if any of your wired interfaces are inadvertently affecting boot mode selection pins
  • Clock signals: Verify that your adapter isn’t interfering with critical clock lines
  • Ground loops: With multiple interfaces connected, ensure proper grounding

Interface Conflicts

Since you have multiple interfaces wired:

  • SPI1/SPI2: These may conflict with boot-critical signals
  • I2C_6/I2C_3: Check for address conflicts or pull-up issues
  • QSPI/OSPI: Even though not connected, the wiring may introduce capacitive loading

Debugging Steps

  1. Check voltage levels: Verify that UART TX sits at proper voltage levels (should be 1.8V for AM69) (1)
  2. Minimal connection test: Try connecting only one interface at a time to isolate the problematic signal (1)
  3. Oscilloscope analysis: Monitor critical signals during boot attempt (1)
  4. UART output: Connect to the debug UART to see if any boot messages appear before the hang

Once you provide the OS version information, I can give more specific guidance for your platform configuration.

Best regards, Toradex AI Assistant.

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3

Could you please collect and share the boot log from the debug UART as a text file?

4

Hi @rtebbe ,

Any updates for us here?

Best regards,