STM32F407 GPIO (operation register)

GPIO

The stm32f407VG microcontroller has a total of 5×16 PA-PE and a total of 80 multiplexed IO ports. Each general I/O port has four 32-bit configuration registers (GPIOx_MODERGPIOx_OTYPERGPIOx_OSPEEDRGPIOx_PUPDR), two 32-bit data registers (GPIOx_IDR and GPIOx_ODR), a 32-bit set/reset register (GPIOx_BSRR), a 32-bit lock register (GPIOx_LCKR) and two 32-bit alternate function selection registers (GPIOx_AFRHGPIOx_AFRL).

Setup steps:

1. Enable the relevant clock

2. Set the corresponding IO port as input or output

3. Set the input\output type

4. Set the output speed (if set to input, skip this step)

5. If the output speed is >= 50M, turn on the compensation unit

6. Set the pull-up and pull-down registers

7. Operate through the reset register and input and output data register.

program:

[cpp] view plaincopy

/************************************ 

    Title: Exercise on operating GPIO 

    Software platform: IAR for ARM6.21 

    Hardware platform: stm32f4-discovery 

    Main frequency: 168M 

    author: Xiaochuan 

    data: 2012-01-16 

*************************************/  

#include   

uint32_t Gb_TimingDelay;  

void Delay(uint32_t nTime);  

void main ()  

{     

  SysTick_Config(SystemCoreClock / 1000); //Set systemtick one millisecond interrupt  

  RCC->AHB1ENR |= 0x00000008; //Enable GPIOD clock  

  RCC->APB2ENR |= (1<<14); //Enable syscfg clock  

  GPIOD->MODER &= 0x00FFFFFF; //Set PD12,13,14,15 output  

  GPIOD->MODER |= 0x55000000;   

  GPIOD->OTYPER &= 0xFFFF0FFF; //Set PD12,13,14,15 push-pull output  

  GPIOD->OSPEEDR &= 0x00FFFFFF; //PD12,13,14,15 speed 100m  

  GPIOD->OSPEEDR |= 0xff000000;  

  SYSCFG->CMPCR = 0x00000001; //Use IO compensation unit,  

//When the GPIO speed exceeds 50M, consider using this setting  

  GPIOD->PUPDR &= 0x00FFFFFF; //PD12,13,14,15 no pull-up no pull-down  

  GPIOD->BSRRH = 0xf000; //reset register GPIOx_BSRRH, write only  

                            //set register GPIOx_BSRRL, write only  

  while(1)  

  {  

      GPIOD->BSRRH = 0xf000;  

      GPIOD->BSRRL = 0x1000;   

      Delay(500);  

      GPIOD->BSRRH = 0xf000;  

      GPIOD->BSRRL = 0x1000<<1;  

      Delay(500);  

      GPIOD->BSRRH = 0xf000;  

      GPIOD->BSRRL = 0x1000<<2;  

      Delay(500);  

      GPIOD->BSRRH = 0xf000;  

      GPIOD->BSRRL = 0x1000<<3;  

      Delay(500);  

  }  

}  

void Delay(uint32_t nTime)  

{   

  Gb_TimingDelay = nTime;  

  while(Gb_TimingDelay != 0);  

}  

void SysTick_Handler(void)  

{  

  if (Gb_TimingDelay != 0x00)  

  {   

    Gb_TimingDelay--;  

  }  

}