/* p7_4.c: Use DAC to generate sawtooth waveform
 * The DAC is initialized with no buffer or trigger, so every 
 * write to the DAC data register will change the analog output.
 * The data is incremented in the loop and written to the DAC.
 * The output of DAC is on pin PA4.
 *
 * This program was tested with Keil uVision v5.24a with DFP v2.11.0.
 */
#include "stm32f4xx.h"

int main(void) {
    int data;
    RCC->AHB1ENR |=  1;	            /* enable GPIOA clock */    
    GPIOA->MODER |=  0x00000300;    /* PA4 analog */
    /* setup DAC */
    RCC->APB1ENR |= 1 << 29;        /* enable DAC clock */
    DAC->CR |= 1;                   /* enable DAC */

    while(1) {        
        DAC->DHR12R1 = data++ & 0x0FFF;
    }
}