/* Use DAC_MCP4725 of the Edubase board via I2C.
 *
 * The program generates sinewave output through DAC, which 
 * is connected via I2C. The I2C connections are:
 * I2C1_SCL - PB08
 * I2C1_SDA - PB09
 *
 * Put speaker select jumper on DAC and you will hear the tone.
 *
 */

#include "stm32f4xx.h"

#define SLAVE_ADDR 0x60     /* 1100 xx0. */

void I2C1_init(void);
int I2C1_burstWrite(char saddr, char maddr, int n, char* data);
void MCP4725_data(int n);

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

int main(void) {
    int i;

    I2C1_init();

    for (;;) {  /* infinite loop */
        for (i = 0; i < sizeof(sineWave)/sizeof(int); 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) {
    RCC->AHB1ENR |=  2;                     /* Enable GPIOB clock */
    RCC->APB1ENR |=  0x00200000;	        /* Enable I2C1 clock */

    /* configure PB8, PB9 pins for I2C1 */
    GPIOB->AFR[1]   &= ~0x000000FF;         /* PB8, PB9 I2C1 SCL, SDA */
    GPIOB->AFR[1]   |=  0x00000044;
    GPIOB->MODER    &= ~0x000F0000;         /* PB8, PB9 use alternate function */
    GPIOB->MODER    |=  0x000A0000;
    GPIOB->OTYPER   |=  0x00000300;         /* output open-drain */
    GPIOB->PUPDR    &= ~0x000F0000;         /* with pull-ups */
    GPIOB->PUPDR    |=  0x00050000;

    I2C1->CR1       =   0x8000;             /* software reset I2C1 */
    I2C1->CR1       &= ~0x8000;             /* out of reset */
    I2C1->CR2       =   0x0010;             /* peripheral clock is 16 MHz */
    I2C1->CCR       =   80;                 /* standard mode, 100kHz clock */
    I2C1->TRISE     =   17;                 /* maximum rise time */
    I2C1->CR1       |=  0x0001;             /* enable I2C1 module */
}

/* 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(char saddr, char maddr, int n, char* data)
{
    int i;
    volatile int tmp;

    while (I2C1->SR2 & 2);                  /* wait until bus not busy */
    I2C1->CR1 &= ~0x800;                    /* disable POS */
    I2C1->CR1 |= 0x100;                     /* generate start */
    while (!(I2C1->SR1 & 1));               /* wait until start flag is set */
    I2C1->DR = saddr << 1;                  /* transmit slave address */
    while (!(I2C1->SR1 & 2));               /* wait until addr flag is set */
    tmp = I2C1->SR2;                        /* clear addr flag */
    while (!(I2C1->SR1 & 0x80));            /* wait until data register empty */
    I2C1->DR = maddr;                       /* send memory address */

    /* write all the data */
    for (i = 0; i < n; i++) {
        while (!(I2C1->SR1 & 0x80));        /* wait until data register empty */
        I2C1->DR = *data++;                 /* transmit memory address */
    }

    while (!(I2C1->SR1 & 4));               /* wait until transfer finished */
    I2C1->CR1 |= 0x200;                     /* generate stop */

    return 0;
}

/* 16 MHz SYSCLK */
void delayMs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 3195; i++) ;
}