/* I2C_DAC_MCP4725 via I2C
 *
 * The program generates sinewave output through DAC.
 *  I2C1SCL PA6
 *  I2C1SDA PA7
 * Put speaker jumper on DAC and you will hear the tone.
 *
 * Built and tested with Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123GH6PM.h"

#define SLAVE_ADDR 0x60     // 1100 xx0.

void I2C1_init(void);
int I2C1_burstWrite(int slaveAddr, char command, int byteCount, const char* data);
void delayMs(int n);
static int I2C_wait_till_done(void);
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);
}

// initialize I2C1 as master and the port pins
void I2C1_init(void) {
    SYSCTL->RCGCI2C |= 0x02;    // enable clock to I2C1
    SYSCTL->RCGCGPIO |= 0x01;   // enable clock to GPIOA

    // PORTA 7, 6 for I2C1
    GPIOA->AFSEL |= 0xC0;       // PORTA 7, 6 for I2C1
    GPIOA->PCTL &= ~0xFF000000; // PORTA 7, 6 for I2C1
    GPIOA->PCTL |= 0x33000000;
    GPIOA->DEN |= 0xC0;         // PORTA 7, 6 as digital pins
    GPIOA->ODR |= 0x80;         // PORTA 7 as open drain

    I2C1->MCR = 0x10;           // master mode
    I2C1->MTPR = 24;            // 100 kHz @ 50 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 & 1);   // wait until I2C master is not busy
    return I2C1->MCS & 0xE; // return I2C error code
}

// Use burst write to write multiple bytes to consecutive locations
// burst write: S-(saddr+w)-ACK-command-ACK-data-ACK-data-ACK-...-data-ACK-P
int I2C1_burstWrite(int slaveAddr, char command, int byteCount, const char* data) {
    char error;

    if (byteCount <= 0)
        return -1;                  // no write was performed

    // send slave address and starting address
    I2C1->MSA = slaveAddr << 1;
    I2C1->MDR = command;
    I2C1->MCS = 3;                  // S-(saddr+w)-ACK-maddr-ACK

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

    // send data one byte at a time
    while (byteCount > 1)
    {
        I2C1->MDR = *data++;             // write the next byte
        I2C1->MCS = 1;                   // -data-ACK-
        error = I2C_wait_till_done();
        if (error) return error;
        byteCount--;
    }

    // send last byte and a STOP
    I2C1->MDR = *data++;                 // write the last byte
    I2C1->MCS = 5;                       // -data-ACK-P
    error = I2C_wait_till_done();
    while(I2C1->MCS & 0x40);             // wait until bus is not busy
    if (error) return error;

    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 */
}