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Power-up problem STM32L4

Question asked by Alvar Ollon on Dec 21, 2017
Latest reply on Dec 22, 2017 by Alvar Ollon


Having a problem to startup the STM32L4 MCU. After powering the board it seems like the controller does not start or get stuck. Running with a debugger works fine but when removing the debugger connection and power cycle the board, the controller does not run. I also tested to add an external watchdog and the controller started and behaved as expected. So I started to think that the reset (NRST) pin had to do with the problem. I removed the external watchdog and power cycled the board then I manually reset the MCU by shortly connected the NRST to ground. The MCU started to run as expected.


I would prefer to run without an external watchdog and without a manual reset. I am asking for help to understand why this is happening and how to solve the problem.