I’ve designed a custom carrier board for the Verdin AM62 SoM and I’m running into a boot issue.
The board powers up correctly, I’ve confirmed that.
Specifically, I manually pulled CTRL_WAKE1_MICO high to 1.8V to ensure proper startup behavior.
I’m trying to boot the Verdin AM62 from an SD card, and for that I copied the SD-card circuit from the Verdin Development Carrier Board reference design.
However, I’m not getting any signal output on UART3 or UART4. I was expecting to see boot messages, but both UARTs are completely silent. I’m thinking that the AM62 is just not starting up.
Steps I’ve taken:
Verified 1.8V power rails.
Pulled CTRL_WAKE1_MICO high to 1.8V.
SD-card boot layout is identical to Toradex’s reference.
Tried both UART3 and UART4 as debug console, just in case.
The AM62 is working because i tried it on the Dahlia carier board.
On the Dahlia carrier board the device is booting also from SD-card.
I’m wondering:
Is there a known difference in behavior when booting from SD that would prevent UART output?
Why would a AM62 just not start up?
Any insight or debugging tips would be appreciated!
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Hello! Thank you for reaching out and providing such a detailed description of your setup and troubleshooting steps.
Here’s some guidance and possible next steps based on your scenario:
1. UART Console Expectations
On Verdin AM62, UART_3 is the designated primary debug console (reference).
UART_4 is considered a secondary debug port. For standard console output during boot, UART_3 should be used.
Double-check that you have correctly mapped the UART_3 TX/RX signals to your debug connector and that any voltage level translators are suitable for 1.8V I/O.
2. Power and Reset Signals
If the module works on the Dahlia carrier board but not yours, focus on essential non-SOM circuits: supply rails, RESET_MICO# (should be held high), CTRL_WAKE1_MICO, and boot signal wiring.
Confirm all “Always Compatible” pins—including power, ground, reset, and essential control signals—are routed as per the Verdin AM62 specification.
3. SD Card Boot
There’s no difference in UART output based on boot source (eMMC or SD) as long as the SD card is wired up per the reference design and contains a valid boot image.
If the SD card is not found (for example, data or command lines are not connected, or there’s a voltage mismatch), the module may not boot past the ROM loader, resulting in no UART output.
Make sure your SD card socket, card detect, and SD lines (DAT0-3, CMD, CLK) are connected exactly as in the reference design. Use 1.8V for IO as required by the module.
4. Debugging Tips
Check voltage on UART_3 TX: If it sits at 0V, the SoM may not be starting or is held in reset. If it’s at 1.8V but silent, the SoM may be running but unable to boot for other reasons.
Check RESET_MICO# and PMIC signals: Ensure RESET_MICO# is not held low by your carrier. If possible, monitor the PMIC_EN and PMIC_IRQ signals.
Test with minimal connections: Remove as many peripherals as possible and power the board with only the bare minimum connected (power, reset, UART_3).
Oscilloscope UART signals: Check for any activity, even “garbage” data—any sign of line toggling can provide clues.
5. Carrier Board Differences
Since your SoM works on Dahlia, suspect a missing or incorrectly connected critical signal on your board.
No special pinmux or EEPROM is needed for SD card boot or UART debug out of the box.
In summary:
Focus on verifying RESET_MICO#, power rails, and “Always Compatible” signals. Double-check your SD card circuitry and verify UART_3 TX connections. If everything appears correct, try powering up with the USB debug/UART attached and see if any data (even at the wrong baud) is visible.
If you want a step-by-step checklist for board bring-up or have a specific schematic question, please let me know!
Have you written a device tree for your custom board? Have you tested it with a default image?
I’m not aware of any issue related to booting from an SD card and not being able to see UART output, so I would say that it could be some hardware issue.
