STM32F4 Discovery : GPIO

The most basic thing one would do with an MCU would be how to control the IO pins right? So how do we program the GPIO pins on STM32F4Discovery board?
Let's take a look at it now,

First and foremost we need to add stm32f4xx_gpio.h and stm32f4xx_rcc.h header files to be included in the project.

Once that is done we must enable clock to the port (whichever port you would like to use)

Each peripheral bus is detailed in the datasheet and we can use this information to enable system clock programmatically based on our application.

	// enables HSE oscillator
	RCC_HSEConfig(RCC_HSE_ON);
	// wait till clock stabilizes
	while(!RCC_WaitForHSEStartUp()) {
	}
	//enables clock to portD
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD,ENABLE);

view raw stm32f4_clock_enable.c hosted with ❤ by GitHub

Then we have to set parameters for configuring GPIO pins

	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Pin=GPIO_Pin_14;
	GPIO_InitStructure.GPIO_Mode=GPIO_Mode_OUT;
	GPIO_InitStructure.GPIO_OType=GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_NOPULL;
	GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
	GPIO_Init(GPIOD,&GPIO_InitStructure);

view raw STM32F4_GPIO_Init.c hosted with ❤ by GitHub

The various options are self explanatory.You can adjust the settings based on your application.

Now lets try to toggle pin14 from PORTD which is an onboard LED on our discovery board.

	// Toggle pin
	while(1) {
	GPIO_SetBits(GPIOD,GPIO_Pin_14);
	delay(0x0000FFFF);
	GPIO_ResetBits(GPIOD,GPIO_Pin_14);
	delay(0x0000FFFF);
	}
	return(0);
	}
	// delay function
	void delay(__IO uint32_t count) {
	while(count>0) {
	count--;
	}
	}

view raw STM32F4_Pin_Toggle.c hosted with ❤ by GitHub

We've done it! Now you can compile it and see the onboard LED blinking ON and OFF!

So the final code looks something like

	#include "stm32f4xx.h"
	#include "stm32f4xx_gpio.h"
	#include "stm32f4xx_rcc.h"
	void delay(__IO uint32_t);
	int main() {
	RCC_HSEConfig(RCC_HSE_ON);
	while(!RCC_WaitForHSEStartUp()) {
	}
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD,ENABLE);
	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Pin=GPIO_Pin_14;
	GPIO_InitStructure.GPIO_Mode=GPIO_Mode_OUT;
	GPIO_InitStructure.GPIO_OType=GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_NOPULL;
	GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
	GPIO_Init(GPIOD,&GPIO_InitStructure);
	while(1) {
	GPIO_SetBits(GPIOD,GPIO_Pin_14);
	delay(0x0000FFFF);
	GPIO_ResetBits(GPIOD,GPIO_Pin_14);
	delay(0x0000FFFF);
	}
	return(0);
	}
	void delay(__IO uint32_t count) {
	while(count>0) {
	count--;
	}
	}

view raw STM32F4_GPIO_Toggle.c hosted with ❤ by GitHub