/* OLED_SSD1306 via I2C
 *
 * This program communicate with the OLED_SSD1306 via I2C.
 * It writes "ABC" on the display and fills the rest of the
 * display with a checker board pattern.
 *
 *  I2C1SCL PA6
 *  I2C1SDA PA7
 *
 * Built and tested with Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123GH6PM.h"

#define SLAVE_ADDR 0x3C     // 0111 100.
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define SCREEN_PAGE_NUM (SCREEN_HEIGHT / 8)

void SSD1306_init(void);
void SSD1306_data(char data);
void SSD1306_command(char command);
void I2C1_init(void);
int I2C1_byteWrite(int slaveAddr, char memAddr, char data);
void delayMs(int n);
static int I2C_wait_till_done(void);

char imagebuf[SCREEN_PAGE_NUM][SCREEN_WIDTH];

const static char font_table[][6] = {    /* sample font table */
    {0x7e, 0x11, 0x11, 0x11, 0x7e, 0},  /* A */
    {0x7f, 0x49, 0x49, 0x49, 0x36, 0},  /* B */
    {0x3e, 0x41, 0x41, 0x41, 0x22, 0}}; /* C */

int main(void) {
    int i, j, k;

    I2C1_init();
    SSD1306_init();

    SSD1306_command(0x22);              /* set page */
    SSD1306_command(0x00);              /* starting page */
    SSD1306_command(0x00);              /* end page */
    SSD1306_command(0x21);              /* set column */
    SSD1306_command(0);                 /* starting column */
    SSD1306_command(SCREEN_WIDTH-1);    /* end column */
    
    /* write ABC at the beginning of first line */
    for (j = 0; j < 3; j++)
        for (i = 0; i < 6; i++)
            SSD1306_data(font_table[j][i]);

    /* clear the rest of the line */
    for (i = 0; i < SCREEN_WIDTH-3*6; i++)
        SSD1306_data(0);

    for (i = 1; i < SCREEN_PAGE_NUM; i++) {
        SSD1306_command(0x22);              /* set pages */
        SSD1306_command(i);                 /*   starting page */
        SSD1306_command(i);                 /*   end page */
        SSD1306_command(0x21);              /* set columns */
        SSD1306_command(0);                 /*   starting column */
        SSD1306_command(SCREEN_WIDTH-1);    /*   end column */

        /* make checker board pattern */
        for (j = 0; j < SCREEN_WIDTH/8; j++) {
            for (k = 0; k < 4; k++)
                SSD1306_data(0xF0);

            for (k = 0; k < 4; k++)
                SSD1306_data(0x0F);
        }
    }

    for (;;) {  /* infinite loop */
    }
}

const static char init_seq[] = {
    0xae,       // turn off oled panel
    0x00,       // set low column address
    0x10,       // set high column address
    0x40,       // set start line address
    0x20, 0x02, // page addressing mode
    0xc8,       // top-down segment (4th quadrant)
    0x81,       // set contrast control register
    0xcf, 0xa1, // set segment re-map 95 to 0
    0xa6,       // set normal display
    0xa8,       // set multiplex ratio(1 to 64)
    0x3f,       // 1/64 duty
    0xd3,       // set display offset
    0x00,       // not offset
    0xd5,       // set display clock divide ratio/oscillator frequency
    0x80,       // set divide ratio
    0xd9,       // set pre-charge period
    0xf1, 0xda, // set com pins hardware configuration
    0x12, 0xdb, // set vcomh
    0x40, 0x8d, // set Charge Pump enable/disable
    0x14,       // set(0x10) disable
    0xaf        // turn on oled panel
};

void SSD1306_init(void) {
    int i;

    delayMs(100);

	for (i = 0; i < sizeof(init_seq); i++)
        SSD1306_command(init_seq[i]);
}

void SSD1306_data(char data) {
    I2C1_byteWrite(SLAVE_ADDR, 0xC0, data);
}

void SSD1306_command(char command) {
    I2C1_byteWrite(SLAVE_ADDR, 0x80, command);
}

// 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
}

// byte write: S-(saddr+w)-ACK-maddr-ACK-data-ACK-P
int I2C1_byteWrite(int slaveAddr, char memAddr, char data)
{
    char error;

    // send slave address and starting address
    I2C1->MSA = slaveAddr << 1;
    I2C1->MDR = memAddr;
    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
    I2C1->MDR = data;
    I2C1->MCS = 5;                      // -data-ACK-P
    error = I2C_wait_till_done();       // wait until write is complete
    while(I2C1->MCS & 0x40);            // wait until bus is not busy
    error = I2C1->MCS & 0xE;
    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 */
}