Programming Example : GPIO - Analog Mode

#include "stm32f2xx.h"

void GPIO_Config_AnalogMode(void);

int main(void)
{
  GPIO_Config_AnalogMode();  // to be used as ADC input or DAC output
}

void GPIO_Config_AnalogMode(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* Enable GPIOA's AHB interface clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  /* Configure PA4 in analog mode to be used as ADC input */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
}

/*
<Analog mode>

1. Enable GPIOA's AHB interface clock
@reg   RCC->AHB1ENR
@fn    void RCC_AHB1PeriphClockCmd(uint32_t RCC_AHB1Periph, FunctionalState NewState)
@param RCC_AHB1Periph_GPIOA, ENABLE
@ref   stm32f2xx_rcc.h, stm32f2xx.h

2. Configure PA4 in analog mode to be used as ADC input
@reg   GPIOx->MODER, GPIOx->PUPDR
@fn    void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
@param GPIOA, GPIO_Pin_4, GPIO_Mode_AIN, GPIO_PuPd_NOPULL
@ref   stm32f2xx.h, stm32f2xx_gpio.h
*/