/* p9_3.c: burst write to DS1337
 *
 * This program writes the first seven registers of DS1337 using
 * burst write. After the first write, the register address pointer
 * automatically incremented to point to the next register and the 
 * subsequent write goes to the next register. When the last byte 
 * is written, a STOP is generated.
 *
 * No error checking is done in I2C code.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */

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

void I2C1_init(void);
int I2C1_burstWrite(int slaveAddr, unsigned char memAddr, int byteCount, unsigned char* data);

#define SLAVE_ADDR 0x68     // 1101 000.    DS1337

int main(void) 
{
    /*                                 00    01    02    03    04    05    06 */
    unsigned char timeDateToSet[15] = {0x55, 0x58, 0x16, 0x05, 0x19, 0x11, 0x15, 0}; // 2015 November 19, Thu, 16:58:55

    P2->DIR |= 7;   /* P2.2, P2.1 ,P2.0 set as output for tri-color LEDs */

    I2C1_init();

    /* write the first seven bytes of the registers */
    I2C1_burstWrite(SLAVE_ADDR, 0, 7, timeDateToSet);

    for (;;) {
    }
}

/* configure UCB1 as I2C */
void I2C1_init(void) {
    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 3MHz / 30 = 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, unsigned char memAddr, int byteCount, unsigned 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->IFG & 2));      /* wait till it's ready to transmit */
    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 */
}