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 the pin and GPIO port in STM32CubeMX
Modify the code generated by STM32CubeMX and use the HAL functions

2.2 How

Configure the GPIO pin in STM32CubeMX and generate the code
Add into the project the HAL_Delay function and HAL_GPIO_Toggle function
Verify the correct functionality on toggling LED

2.3 Create the 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, the LED pin is already setted (PA5 on NucleoL476RG, for other board check the 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 the Push-pull mode
No pull-up and pull-down
Output speed to VERY HIGH is important for faster peripherals like SPI, USART

File:GPIO config.png

2.3.2 GPIO(Pin) output speed configuration

Change the rising and falling edge when the pin state changes from high to low or low to high
A higher GPIO speed increases the EMI noise from STM32 and increases the STM32 consumption
It is good to adapt the GPIO speed with the peripheral speed. Ex.: Toggling GPIO on 1Hz is LOW optimal settings, but with 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 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 changes.

Warning

All GPIOs are able to drive 5V and 3V in input mode, but they are only able to generate 3V in output Push-pull mode