Hardware failure (Boot Loop) after in-circuit SPI flash

General Discussion
1

I was attempting to flash Libreboot/Coreboot onto a ThinkPad T400 motherboard using a BeagleBone Black (Rev C) and a Pomona 5252 test clip. The target chip is a Macronix MX25L6405D (SOP-16). The BBB was powered via its 5V DC barrel jack.

To handle the 3.3V load, I distributed the power pins across the BBB headers as follows:

  • P9_3 (3.3V) → Pin 2 (VCC)

  • P9_4 (3.3V) → Pin 1 (HOLD#)

  • P8_3 (3.3V) → Pin 9 (WP#)

  • P9_1 (GND) → Pin 10 (GND)

  • Data lines: P9_17 (CS), P9_18 (MOSI), P9_21 (MISO), P9_22 (SCLK)

Immediately upon attaching the clip to the chip, the BBB lost its USB-network connection. Now, with all wires and the SD card removed, the BBB is stuck in a permanent boot loop.

  1. Host PC (Parrot OS): dmesg shows constant connect/disconnect cycles. The interface is renamed to enxdeadbeef0000 before dropping.

  2. BBB LEDs: The Power LED is solid ON. User LEDs D2 and D3 stay solid ON and never flash, indicating the boot process hangs almost immediately.

  3. Looping: The device resets every few seconds.

  • Was using P8_3 and P9_3/4 headers simultaneously for the same VCC/Pull-up rail a mistake that could have damaged the PMIC (TPS65217C)?

  • Does the solid D2/D3 LED state confirm a hardware-level failure in the power delivery system?

  • Is the BBB likely “bricked” due to back-current from the T400 motherboard, or is there a known recovery method for this specific state?

2

Attach something like a Raspberry Pi Debug Probe to your serial, as depicted here:

That should tell you more…

1 Like