Pixhawk 6X "Hard Brick" - No USB enumeration, No SD Card read, Solid B/E LED. Is the Baseboard dead?

Pixhawk
1

Hi everyone,

I am facing a critical issue with my @Holybro Pixhawk 6X (v2b, RC03). The unit seems to be in a “hard brick” state, and I have exhausted standard recovery methods. I am looking for advice on whether this is a recoverable software state or a confirmed hardware failure (Baseboard vs. Cube).

Current Symptoms:

  • LED Status: When powered (via USB or external power), the B/E (Bootloader/Error) LED stays SOLID RED. The ACT (Activity) LED blinks normally.

  • No USB Enumeration: When plugged into a PC (Ubuntu 22.04 and Windows), the device is completely invisible.

    • lsusb returns nothing.

    • dmesg --follow shows absolutely no events when the cable is plugged in (no “device descriptor read error”, just silence).

    • I have tested with multiple known-good USB-C data cables.

  • No SD Card Activity: The bootloader does not seem to access the SD card.

Troubleshooting Steps Taken:

  1. SD Card “Blind” Flash Attempt:

    • I used a verified 8GB Toshiba SD Card. (I checked the SD card’s health with Rufus “Bad Blocks” scan, and it passed with 0 errors)

    • Partition table recreated as MBR (using fdisk), formatted as FAT32 (using mkfs.vfat).

    • Placed the valid PX4 firmware binary renamed to firmware.bin (also tried px4.bin) on the root.

    • Powered on via a stable 65W wall adapter to rule out USB power issues.

    • Result: After minutes of waiting, the file on the SD card remains unchanged (not renamed to .loaded). This suggests the FMU is not communicating with the SD card slot.

  2. Hardware Reseating:

    • I have removed and reseated the Black Cube module from the Baseboard multiple times to ensure the 80-pin connector is seated correctly. No visible bent pins.

  3. Forced DFU Mode (Hardware method):

    • I attempted to force DFU mode by pulling the BOOT0 pin (Pin 3 on the AD&IO port) to 3.3V while powering on.

    • Result: Still no detection in lsusb (no 0483:df11 device appears).

  4. UART/Serial Check:

    • I tried connecting via TELEM1 using a USB-TTL adapter / Raspberry Pi UART.

    • I received no output on the console during boot.

My Diagnosis: Since the CPU seems alive (ACT led blinking) but cannot access peripherals located on the Baseboard (USB PHY, SD Card slot), I suspect a failure in the 80-pin connector or a blown voltage regulator/trace on the Standard Baseboard.

Questions:

  1. Is there any other “backdoor” method to trigger the bootloader on the Pixhawk 6X that bypasses the USB PHY?

  2. Does the failure to read the SD card (despite a proper MBR/FAT32 format) definitively point to a hardware disconnect between the Cube and the Baseboard?

  3. Before I attempt to connect to the FMU DEBUG port for SWD recovery (OpenOCD), is there anything else I should check?

Any insights would be greatly appreciated. Thanks!