Configure GPIO on NUCLEO-L476RG without Cube MX

[DKalm.1]

Hello,

i want to turn the Green USER LED on.

#include "stm32l4xx.h"
#include "stm32l4xx_nucleo.h"
			
 
int main(void)
{
		RCC->AHB2ENR |= RCC_AHB2ENR_GPIOAEN;
		GPIOA->MODER |= GPIO_MODER_MODER5_0;
		GPIOA->ODR |= GPIO_ODR_OD5;
}

So i activated the clock for the Pin and setting the mode(Output) for the LED.

What  have i done wrong ?

thanks,

Dominik

[berendi]

GPIO MODER registers are 0xFFFFFFFF after reset (check the register descriptions in the reference manual) to save some power if the pin is floating.

So the correct way is

GPIOA->MODER &= ~GPIO_MODER_MODER5_1;

or if you are not sure about the register state

GPIOA->MODER = (GPIOA->MODER & ~GPIO_MODER_MODER5) | GPIO_MODER_MODER5_0;

[DKalm.1]

​Oh i see, thank you for your quick answer!

[waclawek.jan]

"Delay after an RCC peripheral clock enabling" erratum may apply, too, although it's not in the 'L4 errata (it's e.g. in the 'F4 errata).

JW

PS. What is "stm32l4xx_nucleo.h"?

[DKalm.1]

Description from the stm32l4xx_nucleo.h file:

This file contains:

* - Configuration section that allows to select:

* - The STM32L4xx device used in the target application

* - To use or not the peripheral’s drivers in application code(i.e.

* code will be based on direct access to peripheral’s registers

* rather than drivers API), this option is controlled by

* "#define USE_HAL_DRIVER"