Getting started with GPIO

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This article explain what is and how to use GPIO through examplesl

1. GPIO definition

Stands for General Purpose Input/Output. GPIO is a type of pin found on an integrated circuit that does not have a specific function. While most pins have a dedicated purpose, such as sending a signal to a certain component, the function of a GPIO pin is customizable and can be controlled by software.

2. Configure GPIO for LED toggling

2.1. Objective

Learn how to setup pin and GPIO port in STM32CubeMX
Modify code generated by STM32CubeMX and use HAL functions

2.2. Goal

Configure GPIO pin in STM32CubeMX and Generate Code
Add in to project HAL_Delay function and HAL_GPIO_Toggle function
Verify the correct functionality on toggling LED

2.3. Create project in STM32CubeMX

New project > Access to board selector on main panel or Menu > File > New Project
Select NUCLEO-L476RG

File:SelectL476.png

if you have chosen to start the project with a board LED pin is already setted ( PA5 on NucleoL476RG, for other board check User Manual)

Note : whenever you download a firmware package with STM32CubeMX you have existing examples. You can find them for example here : c:\Users\YourUserName\STM32Cube\Repository\STM32Cube_FW_G0_V1.3.0\Projects\NUCLEO-G071RB\Examples\GPIO\GPIO_IOToggle\GPIO_IOToggle.ioc and open them with STM32CubeMX.

2.3.1. GPIO Configuration

Select Push Pull mode
No pull-up and pull-down
Output speed to VERY HIGH is important for faster peripheries like SPI, USART

File:GPIO config.png

2.3.2. GPIO(Pin) output speed configuration

Change the rising and falling edge when pin change state from high to low or low to high
Higher GPIO speed increase EMI noise from STM32 and increase STM32 consumption
It is good to adapt GPIO speed with periphery speed. Ex.: Toggling GPIO on 1Hz is LOW optimal settings, but SPI on 45MHz the VERY HIGH must be set

File:GPIO Speed.png

2.3.3. Set the project details for generation

File:Manage GPIO Project.png

2.3.4. Open the main.c in our IDE

We will do the LED toggling in a function inside main.c

Information

Between /* USER CODE BEGIN 3 */ and /* USER CODE END 3 */ tags

 /* USER CODE BEGIN 3 */
  /* Infinite loop */
  while (1)
  {
    HAL_GPIO_WritePin(GPIOG, GPIO_PIN_14, GPIO_PIN_SET);
    HAL_Delay(500);
    
    HAL_GPIO_WritePin(GPIOG, GPIO_PIN_14, GPIO_PIN_RESET);
    HAL_Delay(500);
  }
  /* USER CODE END 3 */

2.4. Compile and flash

Every 500ms the green LED state change.