Need help for this problem : STM32G070 – PB15 GPIO input always reads LOW with internal pull-up enabled

[naraen_harish]

Hi everyone,

I'm facing an issue while reading a tactile push button connected to PB15 on an STM32G070 series MCU.

The GPIO is configured as an input with an internal pull-up resistor. My expected behavior is:

Button not pressed: GPIO reads HIGH (1). Button pressed: GPIO reads LOW (0).

However, I'm always getting LOW (0), regardless of whether the button is pressed or released.

Here is what I've checked so far:

1. Verified continuity between the button and the MCU pin; it seems fine.

2. Checked the button pin configuration, it looks fine

3. Tried reading the GPIO raw value in code, but it consistently returns 0.

I'm not sure whether I'm missing any thing

Could anyone suggest what I should check next to debug this issue?

I've attached images of the relevant configuration for reference.

Thanks in advance for your help!

 

[waclawek.jan]

​

  

PB15 in ’G07x is the USB-C power delivery Dead-battery pin, with the consequence of having a pulldown controlled by another pin and a control bit - this is the case also of ‘G070 even if it’s a Value line and does not officially have the USBC-PD features.

This *is* actually documented in the DS, although not necessarily obvious from just clicking in CubeMX.

JW

​

[MOBEJ]

Hello ​@naraen_harish , 

As ​@waclawek.jan mentioned, PB15 has a separate dead-battery pull-down that could explain this. Try disabling it during startup:

__HAL_RCC_SYSCFG_CLK_ENABLE();
HAL_SYSCFG_StrobeDBattpinsConfig(SYSCFG_UCPD1_STROBE |SYSCFG_UCPD2_STROBE);

Keep PB15 configured as input with pull-up. Does it now read HIGH when the button is released?

Br

[Andrew Neil]

Here is what I've checked so far:

1. Verified continuity between the button and the MCU pin; it seems fine.

2. Checked the button pin configuration, it looks fine

3. Tried reading the GPIO raw value in code, but it consistently returns 0.

But have you measured the actual voltage at the PB15 pin?

If that voltage is constantly low then, of course, the GPIO will always read 0 - so you’d need to look for what is pulling it down (probably ​@waclawek.jan has answered that)

 

See also:

 

For posting source code, please see:

 

[naraen_harish]

Thank you ​@waclawek.jan  for your insight. It was really helpful. Now it’s working fine

[naraen_harish]

Thanks ​@MOBEJ ​@Andrew Neil . Now the issue resolved based on information provided by ​@waclawek.jan