#include "stm32f4xx.h"
#include "stm32f4xx_rcc.c"
#include "stm32f4xx_dac.c"
#include "stm32f4xx_gpio.c"

// DAC init function
void DACinit (void)     {
DAC_InitTypeDef         DAC_InitStructure;
GPIO_InitTypeDef        GPIO_InitStructure;
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_4 | GPIO_Pin_5;
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;  
  GPIO_Init(GPIOA, &GPIO_InitStructure);  
  
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
  DAC_InitStructure.DAC_OutputBuffer                 = DAC_OutputBuffer_Enable;
  DAC_InitStructure.DAC_Trigger                      = DAC_Trigger_None;
  DAC_InitStructure.DAC_WaveGeneration               = DAC_WaveGeneration_None;
  DAC_Init(DAC_Channel_1, &DAC_InitStructure); 
  DAC_Init(DAC_Channel_2, &DAC_InitStructure);
  
  DAC_Cmd(DAC_Channel_1, ENABLE);   
  DAC_Cmd(DAC_Channel_2, ENABLE);
}

int main ()  {                  
unsigned int j;
  
  DACinit();
  
  while (1) {
    DAC->DHR12R1 = j & 0xfff;           // up ramp
    DAC->DHR12R2 = 0xfff - (j & 0xfff); // down ramp
    j = (j + 1) & 0x0fff;
  };
};