STM32F446RE Can't use Pins PA2, PA3 as Input

[FLewz.1]

Hi,

I am trying to use the PA2 and PA3 Pins among others as Inputs with Pullups. The configuration is correct, since I am comparing what is in the GPIO Registers for Port A with another input pin PA8 which works fine. I have seen that the same pins use serial and analog input, however I have not initialized serial and I guess to use the analog input you have to initialize it in the mode register? I am using the ADC but I have not configured these pins for analog input.

Am I missing something, that is keeping me from using these pins?

[Uwe Bonnes]

Analog input with internal PullUP is marked as reserved.

[waclawek.jan]

Please state clearly, what do you intend to do, and how the present state is different from your expectations.

Do this together with posting the relevant GPIO registers' settings.

JW

[FLewz.1]

So using an external pullup would solve my problem?

[FLewz.1]

I am trying to use PA2 and PA3 as inputs with pullups, to register when it gets pulled low. Now it doesn't register when pulled low.

GPIO_InitStruct.Pin = IN0_PIN;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_PULLUP;
HAL_GPIO_Init(IN0_PORT, &GPIO_InitStruct);

That's the InitStruct with IN0_PIN being GPIO_PIN_2 and IN0_PORT being GPIOA.

The same struct is being used on pin PA8 for example, where it works and the pin successfully reads as GPIO_Pin_RESET when pulled low.

[FLewz.1]

To add the register values after configuration:

MODER2 0x0
MODER3 0x0
 
PUPDR2 0x1
PUPDR3 0x1
 
IDR3 0x1
IDR2 0x1

The other registers are at reset value, so no alternate function mapping or anything.

[waclawek.jan · Accepted solution]

Manipulate the PA2/PA3 pins while observing GPIOA_IDR in the debugger.

Is this a "known good" board such as a Nucleo64?

What's connected to those pins? (If it's Nucleo64, then disconnect the STLINK VCP connections, SB13, SB14, and connect SB62, SB63, see UM1724).

JW

[FLewz.1]

Yes it's a nucleo board. But your hint to the User Manual solved my problem, since those are the two UART pins, although I figured disabling UART2 would suffice. Unfortunately I'll have to rethink my external hardware connection.

Thank you!