cancel
Showing results for 
Search instead for 
Did you mean: 

Program not running when powering from external source

DavidL_
Associate III

I have an L432KC and to test it, I created a simple blinking program which I uploaded via USB, which works just fine. When connecting my MCU to my external 5V power supply though, my program does not run. Looking at some posts, I found people suggesting to pull down the Boot0 pin to ensure that it loads the user program, I am not able to find the Pin name on the board of the Boot0 pin of the L432KC though.

I'd appreciate it if someone could help me out.
Thanks in advance!

1 ACCEPTED SOLUTION

Accepted Solutions

@DavidL_ wrote:

How would I „break“ this link? What exactly does that mean?


It's here:

AndrewNeil_0-1727192204016.png

 

The photo in the UM shows a zero-ohm resistor fitted:

AndrewNeil_1-1727192253286.png

To break the link, you need to remove that zero-ohm link.

There's no need to be particularly careful with it - you don't need to keep it - so just heat it up with a soldering iron until it comes off.

 

@SofLit @STTwo-32 I've noted before that this needs to be better documented:

https://community.st.com/t5/stm32-mcus-products/docmentation-of-solder-bridges/m-p/689362

 

#BreakSolderBridge #SolderBridge #SB

View solution in original post

18 REPLIES 18
TDK
Guru

You're connecting 5V to CN4 pin 4 and GND to GND somewhere?

Are you relying on the clock from the ST-Link chip? Use HSI instead.

Unlikely BOOT0 is the issue here as it is pulled down by default, unless you've modified solder bridges.

If you feel a post has answered your question, please click "Accept as Solution".
DavidL_
Associate III

I see no CN4 pin on the boar, I have a "5V" pin that i connect my external power source to.

The user manual has instructions for powering the board externally. I suggest following those. Perhaps a picture of what you're doing would help. All connectors are named.

If you feel a post has answered your question, please click "Accept as Solution".

@DavidL_  You haven't said what board you're using!

 


@TDK wrote:

Are you relying on the clock from the ST-Link chip? Use HSI instead.


Also, if the on-board ST-Link is not powered, it's likely to pull the Target's NRST pin down - which will hold the target in Reset ...

DavidL_
Associate III

I am simply connecting my power supply to the „5V“ pin and ground to GND.

 

I read through the section in the pdf i found for the board, but these weren’t exactly instructions, more like infos.

I mentioned in my first comment that I have a L432KC board.

I tried erasing everything from the MC via the STM Programmer, but i got an error indicating that the reset is pulled down, so that seems plausible.

 

Does the ST-Link chip need to be powered individually?


@DavidL_ wrote:

I mentioned in my first comment that I have a L432KC board.


That's just a chip part number - it doesn't identify a board.

Do you mean a Nucleo-L432KC board?

https://community.st.com/t5/stm32-mcus-products/communication-between-nucleo-f411re-and-raspberry-pi-using-st/m-p/721506/highlight/true#M261161

 


@DavidL_ wrote:

Does the ST-Link chip need to be powered individually?


The thing is, the ST-Link on Nucleo boards provides two things to the Target microcontroller:

  1. The clock signal
  2. The NRST signal

So, if the ST-Link is not powered, the Target will get no clock, and its NRST line will be pulled low.

There should be a link you can break to disconnect the NRST signal.

You can also break-off the ST-Link section of the board. <-- Sorry, not on this board - that only applies to Nucleo-64

 

https://community.st.com/t5/stm32-mcus-products/measuring-ground-current-does-not-seem-to-match-datasheet-on/m-p/716720/highlight/true#M259890

 


@Andrew Neil wrote:

 

 

There should be a link you can break to disconnect the NRST signal.

It's SB9:

AndrewNeil_0-1727187741074.png

 

 


 

Thanks for the clarification, I have a Nucleo-32 L432KC.

Do i want the NRST to be low or high if I want my user code to be run at startup (or does it even matter)?

 

After some errors, I tried to erase the contents of the chip, the STM32CubeProgrammer application can recognize the chip, but any flashing attempt fails with a "dev_target_held_under_reset" error.

 

There is a physical jumper from GND to NRST, do i want to keep it on?