Verdin Customized Carrier board: no HDMI output, Recovery not work

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Troubleshooting Your Custom Carrier Board Issues

Based on your description of the custom carrier board using the Mallow v1.1 design with only connector changes, here are the likely causes and solutions for your issues:

1. HDMI Output Problems

The HDMI output issues you’re experiencing are similar to a known problem with early Mallow carrier board revisions (1). The Verdin iMX8M Plus includes comprehensive HDMI support with signals including HDMI_1_HPD, HDMI_1_CEC, and differential pairs for HDMI_1_TXC and HDMI_1_TXD0-2 (2).

Potential solutions:

  • Check HDMI cable and display compatibility - Try different HDMI cables and displays to rule out compatibility issues with color space, bit depth, resolution, refresh rate, or EDID (1)
  • Verify HDMI connector implementation - Ensure your connector changes didn’t affect the HDMI signal integrity or pin assignments (2)
  • Test with different display modes - The bootargs show video configuration: video=HDMI-A-1:1280x720-16@60D video=HDMI-A-2:1280x720-16@60D (1)

2. Recovery Mode Connection Issues

For recovery mode troubleshooting, the Verdin iMX8M Plus uses a dedicated recovery mechanism (3):

Recovery Mode Requirements:

  • The dedicated recovery pin (SODIMM pin 246) needs to be pulled down with <1kΩ during initial power on (cold boot) to enter recovery mode (3)
  • Ensure no bootable SD card is present, as the module will try to boot from external SD card instead of entering USB serial loader (3)
  • USB_1 interface must be accessible for recovery mode functionality (3)

Connection verification steps:

  • Verify the CTRL_RECOVERY_MICO# function on SODIMM pin 246 is properly implemented (3)
  • Check that your connector changes didn’t affect the USB_1 interface routing
  • Confirm the recovery pin can be properly pulled low during power-on

3. Additional Debugging Options

Since HDMI output is problematic, consider alternative debugging methods:

UART Console Access:

  • UART_3 provides console access for the main CPUs (A53) (3)
  • UART_4 is available for debugging the M7 core (3)
  • These should be accessible even when HDMI output fails

Network-based Access:

  • The Easy Installer supports VNC access over network connection (1)
  • Use ip addr show to display Ethernet IP addresses or USB NCM at IP 192.168.11.1 (1)

4. Design Verification

Even with identical circuitry to the Mallow v1.1 design, verify:

  • All power rails are stable, especially the 1.8V reference for JTAG (SODIMM pin 7) (2)
  • Signal integrity wasn’t compromised by the connector changes
  • Ground connections and power distribution remain intact

The fact that the SOM works on the original carrier board confirms the module itself is functional, pointing to implementation differences in your custom design.

Best regards, Toradex AI Assistant.