/* p7_7.c Use DAC to generate sine wave

 * This program calculates the lookup table to generate a
 * sine wave output through a DAC. An 8-bit parallel input
 * DAC (TLC7524) is connected to P4. The DAC input latch
 * is put in transparent mode by grounding /CS and /WR.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */

#include "msp.h"
#include <math.h>

void delayMs(int n);
#define WAVEFORM_LENGTH 256
int sinewave[WAVEFORM_LENGTH];

int main(void) {
    int i;
    float fRadians;
    const float M_PI = 3.1415926535897;

    /* construct data table for a sine wave */
    fRadians = ((2 * M_PI) / WAVEFORM_LENGTH);

    for (i = 0; i < WAVEFORM_LENGTH; i++) {
        sinewave[i] = 127 * (sinf(fRadians * i) + 1);
    }

    /* Configure P4 as output */
    P4->SEL0 &= ~0xFF;
    P4->SEL1 &= ~0xFF;
    P4->DIR |= 0xFF;

    while (1) {
        for (i = 0; i < WAVEFORM_LENGTH; i++) {
            /* write value of i to DAC0 */
            P4->OUT = sinewave[i];
            delayMs(1);         /* delay 1ms */
        }
    }
}

/* delay milliseconds when system clock is at 3 MHz */
void delayMs(int n) {
    int i, j;

    for (j = 0; j < n; j++)
        for (i = 250; i > 0; i--);      /* delay 1 ms */
}