RTC DS1307 on EduARM4 Trainer Board

/*

* I2C to DS1307 single byte writes

* This program communicates with the DS1307 Real-time Clock via I2C.

*

* The DS1307 has a total of 64 bytes of RAM space with addresses 00–3FH.

* The first seven locations, 00–06, are set aside for RTC values of Time and Date.

* The next byte is used for the control register. It is located at address 0x07.

* That leaves 56 bytes, from addresses 0x08 to 0x3F, available for general-purpose data storage.

* That means the entire 64 bytes of RAM are accessible directly for read or write

*

*/

/* DS1307 parameters:  fmax = 100 kHz

 *                     I2C1SCL PA6

 *                     I2C1SDA PA7

 *

*/

#include <stdint.h>

#include "inc/tm4c123gh6pm.h"

#define MAX_BUF_SIZE                56

#define SLAVE_ADDR 0x68             /* 1100 1000 */

#define I2C_START_ADDR              0x08

void I2C1_init(void);

char I2C1_byteWrite(int slaveAddr, char memAddr, char data);

char I2C1_read(int slaveAddr, char memAddr, int byteCount, char* data);

char readBuf[MAX_BUF_SIZE];

int main(void)

{

    char err, i;

    char writeBuf;

    writeBuf = I2C_START_ADDR;

    I2C1_init();

    /* write 56 bytes with single byte writes */

    for( i = 0; i < MAX_BUF_SIZE; i++) {

        err = I2C1_byteWrite(SLAVE_ADDR, writeBuf++, i);

        if(err) break;

    }

    if( err ) {

        ;                       /* Handle error condition */

    } else {

        /* uses burst read to read 56 bytes of data */

        err = I2C1_read(SLAVE_ADDR, I2C_START_ADDR, MAX_BUF_SIZE, readBuf);

    }

    for(;;) {

        ;

    }

}

/* initialize I2C1 as master and the port pins */

void I2C1_init(void)

{

    SYSCTL_RCGCI2C_R |= 0x02;       /* enable clock to I2C1 */

    SYSCTL_RCGCGPIO_R |= 0x01;      /* enable clock to GPIOA */

    /* PORTA 7, 6 for I2C1 */

    GPIO_PORTA_AFSEL_R |= 0xC0;     /* PORTA 7, 6 for I2C1 */

    GPIO_PORTA_PCTL_R &= ~0xFF000000; /* PORTA 7, 6 for I2C1 */

    GPIO_PORTA_PCTL_R |= 0x33000000;

    GPIO_PORTA_DEN_R |= 0xC0;       /* PORTA 7, 6 as digital pins */

    GPIO_PORTA_ODR_R |= 0x80;       /* PORTA 7 as open drain */

    I2C1_MCR_R = 0x10;              /* master mode */

    I2C1_MTPR_R = 7;                /* 100 kHz @ 16 MHz */

}

/* Wait until I2C master is not busy and return error code */

/* If there is no error, return 0 */

static int I2C_wait_till_done(void)

{

    while(I2C1_MCS_R & 1)

        ;                           /* wait until I2C master is not busy */

    return I2C1_MCS_R & 0xE;        /* return I2C error code */

}

/* Write one byte only */

/* byte write: S-(saddr+w)-ACK-maddr-ACK-data-ACK-P */

char I2C1_byteWrite(int slaveAddr, char memAddr, char data)

{

    char error;

    /* send slave address and starting address */

    I2C1_MSA_R = slaveAddr << 1;

    I2C1_MDR_R = memAddr;

    I2C1_MCS_R = 3;                 /* S-(saddr+w)-ACK-maddr-ACK */

    error = I2C_wait_till_done();   /* wait until write is complete */

    if(error) return error;

    /* send data */

    I2C1_MDR_R = data;

    I2C1_MCS_R = 5;                 /* -data-ACK-P */

    error = I2C_wait_till_done();   /* wait until write is complete */

    while( I2C1_MCS_R & 0x40 )

        ;                           /* wait until bus is not busy */

    error = I2C1_MCS_R & 0xE;

    if(error) return error;

    return 0;                       /* no error */

}

/* Read memory */

/* read: S-(saddr+w)-ACK-maddr-ACK-R-(saddr+r)-ACK-data-ACK-data-ACK-...-data-NACK-P */

char I2C1_read(int slaveAddr, char memAddr, int byteCount, char* data)

{

    char error;

    if (byteCount <= 0)

        return -1;                  /* no read was performed */

    /* send slave address and starting address */

    I2C1_MSA_R = slaveAddr << 1;

    I2C1_MDR_R = memAddr;

    I2C1_MCS_R = 3;                 /* S-(saddr+w)-ACK-maddr-ACK */

    error = I2C_wait_till_done();

    if(error)

        return error;

    /* to change bus from write to read, send restart with slave addr */

    I2C1_MSA_R = (slaveAddr << 1) + 1;   /* restart: -R-(saddr+r)-ACK */

    if( byteCount == 1 )            /* if last byte, don't ack */

        I2C1_MCS_R = 7;             /* -data-NACK-P */

    else                            /* else ack */

        I2C1_MCS_R = 0xB;           /* -data-ACK- */

    error = I2C_wait_till_done();

    if(error) return error;

    *data++ = I2C1_MDR_R;           /* store the data received */

    if( --byteCount == 0 ) {        /* if single byte read, done */

        while( I2C1_MCS_R & 0x40 )

            ;                       /* wait until bus is not busy */

        return 0;                   /* no error */

    }

    /* read the rest of the bytes */

    while( byteCount > 1 ) {

        I2C1_MCS_R = 9;              /* -data-ACK- */

        error = I2C_wait_till_done();

        if(error) return error;

        byteCount--;

        *data++ = I2C1_MDR_R;        /* store data received */

    }

    I2C1_MCS_R = 5;                 /* -data-NACK-P */

    error = I2C_wait_till_done();

    *data = I2C1_MDR_R;             /* store data received */

    while( I2C1_MCS_R & 0x40 )

        ;                           /* wait until bus is not busy */

    return 0;                       /* no error */

}