General Purpose Input

• The output buffer is disabled.
• The Schmitt trigger input is active.
• The pull-up and -down resistors are active, according to PUPDR.
• Input data is sampled every AHB clock.
• Input data register holds I/O state.

The code snippet bellow shows how to configure and use a GPIO pin as input.

#include "reg_stm32f4xx.h"
 
RCC->AHBENR[0] |= (0x1 << 0u);    /* Enable GPIOA clock */
 
/* Configure GPIO pin A.10 as input. */
GPIOA->MODER &= ~(0x3 << 20u);    /* Clear existing mode bits 20 and 21. */
 
GPIOA->PUPDR &= ~(0x3 << 20u);    /* Clear existing pull-up/-down bits 20 and 21. */
GPIOA->PUPDR |= (0x1 << 20u);     /* Set pin 10 to pull-up mode. */
 
/* Read from GPIO pin A.10. */
uint32_t data = GPIOA->IDR;       /* Read the input data register. */

Hardware Abstraction Layer
Registry Types
InES GPIO HAL Interface

Mode register

Push-up / pull-down register

Input data register

* Register is read only