/* p3_3.c: Initialize and display "hello" on the LCD using 4-bit data mode.

 * All interface uses Port D.  Bit 7-4 are used for data.  
 * Bit 4, 2, 1 are used for control.
 * This program does not poll the status of the LCD.  
 * It uses delay to wait out the time LCD controller is busy.
 * Timing is more relax than the HD44780 datasheet to accommodate the
 * variations of the devices.
 * You may want to adjust the amount of delay for your LCD controller. 
 */

#include <MKL25Z4.H>

#define RS 1    /* BIT0 mask */ 
#define RW 2    /* BIT1 mask */ 
#define EN 4    /* BIT2 mask */

void delayMs(int n);
void delayUs(int n);
void LCD_nibble_write(unsigned char data, unsigned char control);
void LCD_command(unsigned char command);
void LCD_data(unsigned char data);
void LCD_init(void);

int main(void)
{
    LCD_init();
    for(;;)
    {
        LCD_command(1);         /* clear display */
        delayMs(500);
        LCD_command(0x85);      /* set cursor at first line */
        LCD_data('h');          /* write the word */
        LCD_data('e');
        LCD_data('l');
        LCD_data('l');
        LCD_data('o');
        delayMs(500);
    }
}

void LCD_init(void)
{
    SIM->SCGC5 |= 0x1000;       /* enable clock to Port D */ 
    PORTD->PCR[0] = 0x100;      /* make PTD0 pin as GPIO */
    PORTD->PCR[1] = 0x100;      /* make PTD1 pin as GPIO */
    PORTD->PCR[2] = 0x100;      /* make PTD2 pin as GPIO */
    PORTD->PCR[4] = 0x100;      /* make PTD4 pin as GPIO */
    PORTD->PCR[5] = 0x100;      /* make PTD5 pin as GPIO */
    PORTD->PCR[6] = 0x100;      /* make PTD6 pin as GPIO */
    PORTD->PCR[7] = 0x100;      /* make PTD7 pin as GPIO */
    PTD->PDDR |= 0xF7;          /* make PTD7-4, 2, 1, 0 as output pins */

    delayMs(30);                /* initialization sequence */
    LCD_nibble_write(0x30, 0);
    delayMs(10);
    LCD_nibble_write(0x30, 0);
    delayMs(1);
    LCD_nibble_write(0x30, 0);
    delayMs(1);
    LCD_nibble_write(0x20, 0);  /* use 4-bit data mode */
    delayMs(1);
    
    LCD_command(0x28);          /* set 4-bit data, 2-line, 5x7 font */
    LCD_command(0x06);          /* move cursor right */
    LCD_command(0x01);          /* clear screen, move cursor to home */
    LCD_command(0x0F);          /* turn on display, cursor blinking */
}

void LCD_nibble_write(unsigned char data, unsigned char control)
{
    data &= 0xF0;       /* clear lower nibble for control */
    control &= 0x0F;    /* clear upper nibble for data */
    PTD->PDOR = data | control;       /* RS = 0, R/W = 0 */
    PTD->PDOR = data | control | EN;  /* pulse E */
    delayMs(0);
    PTD->PDOR = data;
    PTD->PDOR = 0;
}

void LCD_command(unsigned char command)
{
    LCD_nibble_write(command & 0xF0, 0);   /* upper nibble first */
    LCD_nibble_write(command << 4, 0);     /* then lower nibble */
    
    if (command < 4)
        delayMs(4);         /* commands 1 and 2 need up to 1.64ms */
    else
        delayMs(1);         /* all others 40 us */
}

void LCD_data(unsigned char data)
{
    LCD_nibble_write(data & 0xF0, RS);    /* upper nibble first */
    LCD_nibble_write(data << 4, RS);      /* then lower nibble  */
    
    delayMs(1);
}

/* Delay n milliseconds
 * The CPU core clock is set to MCGFLLCLK at 41.94 MHz in SystemInit().
 */
void delayMs(int n) {
    int i;
    int j;
    for(i = 0 ; i < n; i++)
        for(j = 0 ; j < 7000; j++) { }
}