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Alvar Ollon
Alvar Ollon
Associate
December 21, 2017
Solved

Power-up problem STM32L4

  • December 21, 2017
  • 3 replies
  • 973 views
Posted on December 21, 2017 at 13:38

Hello,

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.

    This topic has been closed for replies.
    Best answer by Tesla DeLorean
    Posted on December 21, 2017 at 13:47

    Make sure BOOT0 is pulled low.

    3 replies

    Tesla DeLorean
    Tesla DeLoreanBest answer
    Guru
    December 21, 2017
    Posted on December 21, 2017 at 13:47

    Make sure BOOT0 is pulled low.

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    John F.
    John F.
    Associate III
    December 22, 2017
    Posted on December 22, 2017 at 09:12

    Do you have a 100nF capacitor connected from Reset to Vss?

    Is your power supply startup ramp monotonic?

    Alvar Ollon
    Alvar OllonAuthor
    Associate
    December 22, 2017
    Posted on December 22, 2017 at 13:26

    Hi,

    The BOOT0 was not connected so I connected BOOT0 to GND and now the controller works as expected.

    Regarding John F’s comment, there is no capacitor between Reset and Vss. It is a capacitor 100nF between Reset and GND. The startup ramp looks fine.

    Thank you both for all help!

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