nRF52840 Custom PCB Stuck in MPU Fault – Works on Other PCBs but Not This One

[manoj_patil]

Hi Nordic DevZone Support,

I am facing an issue with my custom PCB using the nRF52840 microcontroller and Zephyr NCS v2.6.1. The same firmware works on other PCBs, but on this particular board, the code does not reach main() and gets stuck in the MPU fault handler (mem_manage_fault). Additionally, I am not seeing any logs via UART or J-Link RTT.

Observations & Debugging Attempts:

• Power Supply:
  • The MCU receives 3.3V properly.
  • All sensors are powered correctly.
• Same Code Works on Other PCBs but fails on this one.
• Sample Applications Tried:
  • Blinky and Console samples show the same issue.
• Configurations in prj.conf:
  CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n

  CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

  CONFIG_BOARD_ENABLE_DCDC=n
• Debugger Findings:
  • Set a breakpoint at main(), but it never gets hit.
  • The debugger stops at mem_manage_fault(), indicating an early memory issue.
  • Same firmware runs fine on other PCBs (suggesting a board-specific issue).

Questions:

1. What could cause the MPU fault on this specific PCB while the same firmware works on others?
2. Are there any known hardware-level issues (e.g., external components, layout, missing pull-ups, etc.) that could trigger this?
3. Any additional debug steps to identify the root cause?

Any guidance or troubleshooting suggestions would be highly appreciated. Thank you!

[Einar Thorsrud]

Hi,

I see that yo have a crystal and clock configuration that shoudl work on any board. Can you elaborate on how things fail (full error mesage), and describe your board and how it differ from the board where you do not see this error?