/* p7_5.c: Use DAC to generate sine waveform
 *
 * This program uses a pre-calculated lookup table to generate a
 * sine wave output through a DAC.
 * The DAC is initialized with no buffer or trigger, so every 
 * write to the DAC data register will change the analog output.
 * The index of the lookup table is incremented in the loop and 
 * the data is 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"

void delayUs(int n);

int main(void) {
    int i;
    const static int sineWave[] =
        {2048,3071,3821,4095,3821,3071,2048,1024,274,0,274,1024};

    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) {        
        for (i = 0; i < sizeof(sineWave)/sizeof(int); i++)
        {
            DAC->DHR12R1 = sineWave[i]; /* write value of sinewave to DAC */
            delayUs(10);
        }
    }
}

/* 16 MHz SYSCLK */
void delayUs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 3; i++) ;
}