stm32wb5mm-dk external 5V power supply

[matteverze]

Hi, I developed an application using the stm32wb5mm-dk. Everything works until I try to use an external 5V power supply. In fact, I change the position of JP2 on position 7-8 (to select 5V EXT) and I soldered SB4. However, when I supply the board through CN8, LD2 is on, JP1 is at 3.3V but the application on the STM32WB seems not to being run. If I provide power also through the USB STLK, it seems to start running. Is there any other JP or SB to adjust for extenal 5V supply?

Thanks.

[matteverze]

I can add that I verify that the pin NRST goes down when the STLINK is not powered.

[Andrew Neil]

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@matteverze wrote:

the pin NRST goes down when the STLINK is not powered.

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So that will be holding your target in reset.

Presumably, there's a jumper or solder-bridge to disconnect that?

[matteverze]

Hi, from the schematic (https://www.st.com/resource/en/schematic_pack/mb1292-wb5mm-d01-schematic.pdf) NRST is only connected to the STLINK and to the reset push button. No other information is given. Maybe is the STLINK (which is not powered) that pulls down the reset. Seems very strange

[Andrew Neil]

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@matteverze wrote:

 NRST is only connected to the STLINK and to the reset push button. 

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Also to the NRST of the target:

[matteverze · Accepted solution]

Yes, of course. I found a work around. Instead of using the yellow path, I follow the green one, which powers also the ST link. This works.

It seems that if the STLINK is not powered, it push the reset down. This can be a board design issue. 

Thanks

[Andrew Neil]

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@matteverze wrote:

It seems that if the STLINK is not powered, it push the reset down.

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Yes, it would:

https://community.st.com/t5/stm32-mcus-boards-and-hardware/program-not-running-when-powering-from-external-source/m-p/723924/highlight/true#M21543

https://community.st.com/t5/stm32-mcus-boards-and-hardware/external-powering-of-nucleo-l031k6-hsi-able-to-run/m-p/663084/highlight/true#M18423 

That's why there's usually a jumper or solder-bridge to disconnect it.

Seems to be an omission here?

Also an omission from the documentation, which doesn't even mention this - let alone make it clear!

@STTwo-32 

https://www.st.com/resource/en/user_manual/um2825-discovery-kit-with-stm32wb5mmg-module-stmicroelectronics.pdf