General-purpose input/output(GPIO) is the simplest I/O. Each GPIO port has four 32-bit configuration registers (GPIOx_MODER, GPIOx_OTYPER, GPIOx_OSPEEDR and GPIOx_PUPDR), two 32-bit data registers (GPIOx_IDR and GPIOx_ODR), a 32-bit set/reset register (GPIOx_BSRR), a 32-bit locking register (GPIOx_LCKR) and two 32-bit alternate function selection register (GPIOx_AFRH and GPIOx_AFRL). Directly modify the value of register is complicated, so HAL library has define micro and function for us. More over, STM32CubeIDE provides us a more intuitive way to configure each GPIO port. Usage of register in GPIO is not introduced here, check the reference manual of STM32 F1 series for detail.
Each GPIO port in STM32 has 8 modes:
- Input floating
- Input pull-up
- Input pull-down
- Analog
- Output open-drain with pull-up or pull-down capability
- Output push-pull with pull-up or pull-down capability
- Alternate function push-pull with pull-up or pull-down capability
- Alternate function open-drain with pull-up or pull-down capability
Detail of each mode are not introduce here. This blog simply introduce the mode in GPIO and the corresponding feature.
Before using any peripheral, the corresponding peripheral clock need to be enabled first.
void __HAL_RCC_GPIOx_CLK_ENABLE(); // Enable GPIOx ports clock (x can be A, B, C, D...)Initialize the GPIOx peripheral according to the specified parameters in the GPIO_Init,
void HAL_GPIO_Init(GPIO_TypeDef *GPIOx, GPIO_InitTypeDef *GPIO_Init)where GPIO_Init is a struct defined as:
/**
* @brief GPIO Init structure definition
*/
typedef struct
{
uint32_t Pin; /*!< Specifies the GPIO pins to be configured.
This parameter can be any value of @ref GPIO_pins_define */
uint32_t Mode; /*!< Specifies the operating mode for the selected pins.
This parameter can be a value of @ref GPIO_mode_define */
uint32_t Pull; /*!< Specifies the Pull-up or Pull-Down activation for the selected pins.
This parameter can be a value of @ref GPIO_pull_define */
uint32_t Speed; /*!< Specifies the speed for the selected pins.
This parameter can be a value of @ref GPIO_speed_define */
} GPIO_InitTypeDef;Set the fields of GPIO_InitTypeDef and pass it into HAL_GPIO_Init to initialize the corresponding GPIO port.
We also can use graphical way provided by STM32CubeIDE to initialize GPIO. Open the Pinout & Configuration in Pinout view, click a pin and we get a list of peripherals that pin supports. If we want to use the pin to control the LED, we should choose GPIO_Output. If we want to read the key input, we should choose GPIO_Input.
Following is part of the code generated by STM32CubeIDE related to GPIO:
void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_8, GPIO_PIN_RESET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_RESET);
/*Configure GPIO pin : PA8 */
GPIO_InitStruct.Pin = GPIO_PIN_8;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/*Configure GPIO pin : PD2 */
GPIO_InitStruct.Pin = GPIO_PIN_2;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);
}It is clear that STM32CubeIDE firstly enable the corresponding GPIO port clock, then configure the GPIO pin and initialize it.
Some functions used frequently:
On the ALIENTEK MiniSTM32 board, use KEY0 and KEY1 to control two LED DS0 and DS1 individually.
- Find the pins connected to KEY0, KEY1, DS0 and DS1, which are PC5, PA15, PA8 and PD2
- Config the corresponding pin
Following is part of the code generated by STM32CubeIDE related to GPIO:
void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LED0_GPIO_Port, LED0_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = KEY0_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_PULLUP;
HAL_GPIO_Init(KEY0_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = LED0_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LED0_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = KEY1_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_PULLUP;
HAL_GPIO_Init(KEY1_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = LED1_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LED1_GPIO_Port, &GPIO_InitStruct);
}Back to main.c and add the rest part in the while loop:
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
if (HAL_GPIO_ReadPin(KEY0_GPIO_Port, KEY0_Pin) == GPIO_PIN_SET) {
HAL_Delay(100);
HAL_GPIO_TogglePin(LED0_GPIO_Port, LED0_Pin);
}
if (HAL_GPIO_ReadPin(KEY1_GPIO_Port, KEY1_Pin) == GPIO_PIN_SET) {
HAL_Delay(100);
HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
}
}
/* USER CODE END 3 */Compile and program the binary file into the MCU.