/* DAC_MCP4725 via I2C
 *
 * The program generates sinewave output through DAC.
 * I2C1SCL P6.5
 * I2C1SDA P6.4
 * Put speaker jumper on DAC and you will hear the tone.
 *
 * Built and tested with MSP432P401R Rev. C, Keil MDK-ARM v5.24a and MSP432P4xx_DFP v3.1.0
 */

#include "msp.h"

#define SLAVE_ADDR 0x60     // 1100 xx0.

void I2C1_init(void);
int I2C1_burstWrite(int slaveAddr, char command, int byteCount, char* data);
void delayMs(int n);
void MCP4725_data(int n);

const static int sineWave[] =
    {2047,3071,3820,4094,3820,3071,
     2047,1024, 274,   0, 274,1024};

int main(void) {
    short i;

    I2C1_init();

    for (;;) {  /* infinite loop */
        for (i = 0; i < 12; i++)
        {
            MCP4725_data(sineWave[i]);
        }
    }
}

void MCP4725_data(int n) {
    char data[2];
    
    data[1] = (n << 4) & 0xFF;
    data[0] = (n >> 4) & 0xFF;
    I2C1_burstWrite(SLAVE_ADDR, 0x40, 2, data);
}

/* configure UCB1 as I2C */
void I2C1_init(void) {
    extern uint32_t SystemCoreClock;
    EUSCI_B1->CTLW0 |= 1;           /* disable UCB1 during config */
    EUSCI_B1->CTLW0 = 0x0F81;       /* 7-bit slave addr, master, I2C, synch mode, use SMCLK */
    EUSCI_B1->BRW = 30;             /* set clock prescaler for 100kHz */
    P6->SEL0 |= 0x30;               /* P6.5, P6.4 for UCB1 */
    P6->SEL1 &= ~0x30;
    EUSCI_B1->CTLW0 &= ~1;          /* enable UCB1 after config */
}

/* Use burst write to write multiple bytes to consecutive locations
 * burst write: S-(slaveAddr+w)-ACK-memAddr-ACK-data-ACK...-data-ACK-P
 */
int I2C1_burstWrite(int slaveAddr, char memAddr, int byteCount, char* data) 
{
    if (byteCount <= 0)
        return -1;              /* no write was performed */

    EUSCI_B1->I2CSA = slaveAddr;      /* setup slave address */
    EUSCI_B1->CTLW0 |= 0x0010;        /* enable transmitter */
    EUSCI_B1->CTLW0 |= 0x0002;        /* generate START and send slave address */
    while((EUSCI_B1->CTLW0 & 2));   /* wait until slave address is sent */
    EUSCI_B1->TXBUF = memAddr;        /* send memory address to slave */

    /* send data one byte at a time */
    do {
        while(!(EUSCI_B1->IFG & 2));  /* wait till it's ready to transmit */
        EUSCI_B1->TXBUF = *data++;    /* send data to slave */
        byteCount--;
     } while (byteCount > 0);

    while(!(EUSCI_B1->IFG & 2));      /* wait till last transmit is done */
    EUSCI_B1->CTLW0 |= 0x0004;        /* send STOP */
    while(EUSCI_B1->CTLW0 & 4) ;      /* wait until STOP is sent */

    return 0;                   /* no error */
}

/* delay n milliseconds (50 MHz CPU clock) */
void delayMs(int n) {
    int i, j;
    for(i = 0 ; i< n; i++)
        for(j = 0; j < 6265; j++)
            {}  /* do nothing for 1 ms */
}