STM32H755 Nucleo – How to Use PA11, PC14, PC15 as GPIO Output?

[durna]

Hello,

In my project using the STM32H755 Nucleo development board, I need to use PA11, PC14, and PC15 pins as GPIO Output to drive relays. However, when I checked with a digital multimeter, I found that these pins cannot be driven to logic HIGH — they remain stuck at logic LOW.

 

Hardware/Software details:

MCU: STM32H755 (Nucleo-144 board)

IDE/SDK: STM32CubeIDE

 

Project constraint: Almost all pins are already in use, so I have very limited flexibility in choosing alternate pins.

 

After reviewing the technical documentation and the board schematic, I noticed that these pins might be connected to other functions or components. I am attaching the relevant images from the documentation.

Additionally, PE6 is used for the MOSI line of the HI8429 component in my project, so its function must remain unchanged.

 

:pushpin:My question:

Which resistors need to be removed or which solder bridges need to be modified in order to use these pins (PA11, PC14, PC15) as GPIO Output?

Is it possible to make this modification without affecting the PE6 line?

Thank you.

[mfgkw]

According to the schematics PA11 is routed via solder bridge SB26, PC14 through SB66 and PC15 through SB67.

This matches nearly the description in table 16 in UM2408 (PA11-SB27, PA12-SB26). In doubt I would trust the schematics or measure it to be sure.

 

PS: If you want to use PA11 from the morpho connector (close SB22) you will lose PE6 (open SB10) there. So at least one of them must be taken from another connector.

[durna]

 

 

Thank you for your answer. If we look at Table 19, as you said, only one of the PA11 or PE6 pins can be used at the same time.

 

In this case, I can choose a different pin as GPIO_Output instead of PA11, but I definitely need to use the PE6 pin as MOSI. Do I need to complete the solder bridge SB10 in order to use the PE6 pin as MOSI or is it something else?

In order to use PC14 and PC15 pins as GPIO, it is not enough to turn the solder bridges named SB66 and SB67 ON and I also need to remove resistors R41 and R42.

In my work, I need a clock at the MHz level, so I think that not using a 32 KHz oscillator will not cause a problem, am I wrong?