HAL_GPIO_WritePin sets pin on NUCLEO-F446RE but no voltage observed on NUCLEO-WL55JC2

[chandhumallireddy]

Hello STM Community,

I am facing a GPIO output issue on the STM32 NUCLEO-WL55JC2 board and would like some clarification.

Test case:

I am using the following line of code to set a GPIO pin HIGH:

HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_SET); // LED ON

Observation on different boards:

 NUCLEO-F446RE:

• Same code used.

• GPIO pin goes HIGH correctly.

• External LED connected to the pin turns ON.

• Multimeter shows ~3.3 V on the pin.

 NUCLEO-WL55JC2:

• Same code used.

• Code flashes successfully, no errors.

• GPIO pin does not show any voltage when measured with a multimeter.

• External LED connected to the same pin does not turn ON.

• Onboard LEDs (LD1, LD2, LD3) work correctly.

GPIO configuration:

• Pin configured as GPIO Output (Push-Pull) in CubeMX.

• No alternate function selected.

• No pull-up or pull-down enabled.

• Board powered via USB.

• STM32CubeIDE version: v1.19

Key concern:

Even after calling HAL_GPIO_WritePin(..., GPIO_PIN_SET), the GPIO pin on NUCLEO-WL55JC2 does not show 3.3 V, whereas the same code behaves correctly on NUCLEO-F446RE.

Questions:

1. Is GPIOA pin output voltage disabled or isolated by default on NUCLEO-WL55JC2?

2. Does the STM32WL55 require additional power-domain or GPIO enable configuration compared to STM32F4?

3. Are the external GPIO pins on this board routed differently or protected in a way that prevents driving an LED?

4. Is there any board-specific hardware limitation or jumper/solder bridge that must be enabled to get voltage on GPIO pins?

Since onboard LEDs work correctly but external GPIO pins do not output voltage, I suspect this may be related to board-level GPIO power routing or configuration specific to the STM32WL55 / NUCLEO-WL55JC2.

Any guidance would be greatly appreciated.

Thank you

[Peter BENSCH]

You have essentially asked the same question before and confirmed an answer that does not solve your problem yet as the solution.

By the way, could it be that you have confused the cathode and anode?
Why not try the LED the other way round?

Regards
/Peter

[TDK · Accepted solution]

The problem presentation is better this attempt.

> HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_SET); // LED ON

Okay, so you're toggling PA0.

But your wire is connected to PB5.

Make sure you enable GPIOB clock.

[chandhumallireddy]

sorry for the inconvinience, this is my actual piece of code fo toggling the led i was using PB5 pin only

HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, GPIO_PIN_SET); // LED ON 

in pin configuration i had also configured this PB5 GPIO pin only, but still the led did not toggle.

[TDK]

You've marked my answer as the solution again. You shouldn't do this if it didn't solve the problem. You can un-mark it as a solution with the "Not a solution" option in the dropdown.

As for the problem, the PB5 pin works on this chip. So the issue is something specific with your setup or code. I've already pointed out one issue but it's hard to determine what's wrong when the code presented is not what you've used. It's a waste of time to show code that isn't relevant.