/* P9_3.c - Test I2C burst write with DS1337
 *
 * This program initializes the SERCOM1 as I2C and write to
 * all the time registers of the DS1337.
 * PA16 = SDA, PA17 = SCL
 * No errors or acknowledgement are checked.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a.
 */

#include "samd21.h"

unsigned char* ARRAY_PORT_PINCFG0 = (unsigned char*)&REG_PORT_PINCFG0;
unsigned char* ARRAY_PORT_PMUX0 = (unsigned char*)&REG_PORT_PMUX0;

#define SLAVE_ADDR 0x68     /* 1101 000.    DS1337 */

void I2C2_init(void) ;
int I2C2_burstWrite(char saddr, char maddr, int byteCount, char* data);

int main (void) {
    /*                          00    01    02    03    04    05    06 */
    char timeDateToSet[15] = {0x55, 0x58, 0x10, 0x07, 0x26, 0x11, 0x16, 0};
                                /* 2016 November 26, Saturday, 10:58:55 */
    I2C2_init();
    I2C2_burstWrite(SLAVE_ADDR, 0, 7, timeDateToSet);
    
    while (1) {
    }
}

void I2C2_init(void) {
    REG_PM_APBCMASK |= 0x00000008;          /* SERCOM1 bus clock */
    GCLK->CLKCTRL.reg = 0x4015;             /* SERCOM1 core clock */

    ARRAY_PORT_PINCFG0[16] |= 1;            /* allow pmux to set PA16 pin configuration */
    ARRAY_PORT_PINCFG0[17] |= 1;            /* allow pmux to set PA17 pin configuration */
    ARRAY_PORT_PMUX0[8] = 0x22;             /* PA16 = SDA, PA17 = SCL */

    REG_SERCOM1_I2CM_CTRLA = 1;             /* reset SERCOM1 */
    while (REG_SERCOM1_I2CM_CTRLA & 1) {}   /* wait for reset to complete */
    REG_SERCOM1_I2CM_CTRLA = 0x14;          /* master mode */
    REG_SERCOM1_I2CM_BAUD = 0;              /* 1MHz main clock -> ~100KHz I2C clock */
    REG_SERCOM1_I2CM_CTRLA |= 2;            /* enable SERCOM1 */
    REG_SERCOM1_I2CM_STATUS = 0x10;         /* force idle */
}

/* Use burst write to write multiple bytes to consecutive locations
 * burst write: S-(saddr+w)-ACK-maddr-ACK-data-ACK-data-ACK-...-data-ACK-P
 */
int I2C2_burstWrite(char saddr, char maddr, int byteCount, char* data) {
    while((REG_SERCOM1_I2CM_STATUS & 0x30) != 0x10) ; /* wait until idle */
    
    REG_SERCOM1_I2CM_ADDR = saddr << 1;         /* send address */
    while((REG_SERCOM1_I2CM_INTFLAG & 1) == 0); /* wait until saddr sent */

    REG_SERCOM1_I2CM_DATA = maddr;              /* send memory address */
    while((REG_SERCOM1_I2CM_INTFLAG & 1) == 0); /* wait until maddr sent */

    for (; byteCount > 0; byteCount--) {
        REG_SERCOM1_I2CM_DATA = *data++;        /* send data */
        while((REG_SERCOM1_I2CM_INTFLAG & 1) == 0);  /* wait until data sent */
    }

    REG_SERCOM1_I2CM_CTRLB |= 0x30000;          /* issue a stop */
    return 0;
}