Skip to main content
Visitor II
April 15, 2025
Solved

STM32F446 custom, will not boot without debugger

  • April 15, 2025
  • 6 replies
  • 882 views

Custom board will not run without debugger.  With debugger removed and cycling power I have manually touch NRST to ground to get it to run.

The NRST is only connected to SWD pin, but when debugger is removed it is not connected.  Theis is no ST-LINK on the board.  The NRST does measure 3.3 volts after power up.

I do use BOOT0 pin as an output.  It is configured low with pull down in .IOC  (could this be issue?)

Debugger is set to hardware reset, but I have tried all resets.

 

Debugger is set to break at main (not sure if it is trying to break at main without debugger attached?)  I tried to not break at main and will not run with or without debugger.

I also put HAL_DELAY(3000); after Hal_init(),  no difference.

Here is how my clocks are set:

FJB2069_0-1744745563934.png

 

Any suggestions on why it will not run?

    This topic has been closed for replies.
    Best answer by FJB2069

    I found issue.  Pull down resistor on Boot0 had a poor solder joint!

     

    Thanks for all your help!

    6 replies

    Super User
    April 15, 2025

    @FJB2069 wrote:

    Custom board will not run without debugger. 


    Then you'll need to post the schematic

     

    FJB2069Author
    Visitor II
    April 15, 2025

     

     

    FJB2069Author
    Visitor II
    April 15, 2025

    stm32F446.jpg

    Graduate II
    April 15, 2025

    BOOT0 with a local 10K pull-down looks Ok. What do you mean use as Output?

    With a single VCAP I think expectations is for 4.7uF, not 2.2uF

    Super User
    April 15, 2025

    Why is C8 here?

    VSS should be connected directly to ground.

    TDK_0-1744755246280.png

     

    Otherwise seems okay-ish. Should have 0.1 uF decoupling cap on each VDD pin. Unlikely to prevent it from booting.

     

    Voltage at PB0 may be a problem. If using the ADC, voltages above VDDA are not allowed. Included schematic is missing details.

    FJB2069AuthorAnswer
    Visitor II
    April 16, 2025

    I found issue.  Pull down resistor on Boot0 had a poor solder joint!

     

    Thanks for all your help!