Nucleo-G031K8 Program Will Not Start With 12v on VIN Pin LD1 Flashing Slowly

[LAURENCE]

Hi there,

I have a Nucleo-G031K8 evaluation board and am unable to get the program to start when connected to an external power supply. I have a bench top power supply connected to the VIN pin with 12v+ The LD2 led is light indicating power is working but the program fails to initialize and LD1 slowly flashes. The program works as expected when connected to my pc via USB but the program won’t start when using the external supply. The board is in it’s default configuration with respect to jumpers and solder bridges and I opened a brand new unit and attempted to power it via the VIN pin before connecting it to my PCB to verify that no circuit issues or damage is causing this. Please advise.

Thanks

[TDK]

LD2 indicates the device is getting power. Technically, that's the 5V rails and not VDD, but unlikely there are power issues. Likely it's running code somewhere.

LD1 flashing means the USB has not connected to the PC. Do you have a USB cable present?

You can attach a debugger without resetting to see what it's doing. Would be informative to explain what "program won't start" and "works as expected" mean precisely.

Note that 12V is max allowed and that current usage is limited. I'm assuming "12v+" means "+12V" and not "more than 12V".

[LAURENCE]

Hi There,

Thanks for taking the time to review my issue. Hopefully I can provide some more clarity:

1) my power supply is 12v but after the voltage drop through the regulator I get 10v on the VIN pin on the board.

2) I’m using the HAL library via stm32cube ide. Most of the setup code is auto generated. I am using external button interrupts and denouncing with the built in timers. The interrupt callbacks are rising edge and a volatile boolean flag is being set and reset inside the callback.

3) “works as expected�? means the interrupts are working correctly. I am polling for the flag status in my while loop and setting resetting the output GPIO based on the flag also using the HAL_GPIO functions. This is working without fail while connected to the pc via USB.

4) the program doesn’t seem to run while using external power. If I apply 5v power to the 5V pin the program still won’t initialize (I assume it isn’t starting because the button interrupts won’t trigger my outputs as expected) while powering the MCU via the 5V pin I can get it to start working by supplying 3.3v to the RST pin however this is an automotive application so Ideally I would like to power it with the 12v system hence the choice to use the board with “versatile�? power options. I also have already built and wired my pcb with the voltage regulators and i/o protection circuits.

I hope that isn’t just a lot of hot air and helps you understand what I am trying to achieve.

Thanks Again!

[Tesla DeLorean]

Double check what solder bridges are made/open as necessary so the board isn't held in reset.

Is the L1 LED blinking just a secondary effect of what the ST-LINK F103 IC is doing, and not related to what the G031 should be doing?

Have your G031 code do something simple you can validate. Have it self clock, via HSI or MSI, or whatever it starts on.

[TDK]

> my power supply is 12v but after the voltage drop through the regulator I get 10v on the VIN pin on the board.

So you're suppling an external voltage regular with 12V, then using the 10V output to supply the VIN pin? Should be fine, if convoluted. How much current is it using and is the 3.3V line stable?

> I can get it to start working by supplying 3.3v to the RST pin

That's weird. So after supplying VIN power, NRST is low? Forcing this pin high isn't a good idea as it prevents internal resets. If it's low, figure out why and solve that.

Did you attach a debugger to see what it's doing? Although is NRST is low, that's why it's not running.

[LAURENCE]

My apologies I’m relatively new to the STM32 ecosystem here. Do you mean connect pc via USB to use the onboard ST-LINK debugger or connect my dedicated ST-Link dongle? Im not sure how to do that with the SWD pins not exposed on this board. Forgive me if I’m confused here. Seems like the STM32 mcu has a pretty steep learning curve.

[TDK]

Any debugger will work, the onboard one would be a lot simpler.

Looks like your NRST pin is in GPIO mode, so the level on there shouldn't affect the program.

You didn't answer the question about the 3.3V rail.

[Tesla DeLorean]

What firmware is on the ST-LINK?

Can you update to current?

https://www.st.com/en/development-tools/stsw-link007.html

[LAURENCE]

Ok for some reason it is working now. I am not sure exactly why I had already updated the firmware stm32cubeide alerted me of the out of date firmware and offered up the latest version. that said I downloaded the firmware updater via the link you provided and even though the firmware version appeared to be the exact same I updated it again it started working! not sure why that is but I'll take it! Thanks guys!

IF anyone can offer some insight into what mighty have happened there I'm all ears! Also the led is still flashing but the program is working fine. not sure wtf happened there.....

[Tesla DeLorean]

Well I looked over the schematic, and didn't look like the link to the NRST could be disconnected, so the ST-LINK FW is the one blinking the LD1 and clamping the G031's NRST to ground.

ST goes back and forth on how this works