/* p3_2.c: Initialize and display "hello" on the LCD using 8-bit data mode.

 * Data pins use Port D, control pins use Port A.
 * Polling of the busy bit of the LCD status bit is used for timing.
 */

#include <MKL25Z4.H>

#define RS 0x04     /* PTA2 mask */ 
#define RW 0x10     /* PTA4 mask */ 
#define EN 0x20     /* PTA5 mask */

void delayMs(int n);
void LCD_command(unsigned char command);
void LCD_command_noWait(unsigned char command);
void LCD_data(unsigned char data);
void LCD_init(void);
void LCD_ready(void);

int main(void)
{
    LCD_init();
    for(;;)
    {
        LCD_command(1);         /* clear display */
        delayMs(500);
        LCD_command(0xC0);      /* set cursor at 2nd line */
        LCD_data('h');          /* write the word on LCD */
        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[3] = 0x100;      /* make PTD3 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 = 0xFF;           /* make PTD7-0 as output pins */
    
    SIM->SCGC5 |= 0x0200;       /* enable clock to Port A */ 
    PORTA->PCR[2] = 0x100;      /* make PTA2 pin as GPIO */
    PORTA->PCR[4] = 0x100;      /* make PTA4 pin as GPIO */
    PORTA->PCR[5] = 0x100;      /* make PTA5 pin as GPIO */
    PTA->PDDR |= 0x34;          /* make PTA5, 4, 2 as output pins */

    delayMs(20);                /* initialization sequence */
    LCD_command_noWait(0x30);	/* LCD does not respond to status poll */
    delayMs(5);
    LCD_command_noWait(0x30);
    delayMs(1);
    LCD_command_noWait(0x30);
    
    LCD_command(0x38);      /* set 8-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 */
}

/* This function waits until LCD controller is ready to
 * accept a new command/data before returns.
 */
void LCD_ready(void)
{
    char status;
    
    PTD->PDDR = 0;          /* PortD input */
    PTA->PCOR = RS;         /* RS = 0 for status */
    PTA->PSOR = RW;         /* R/W = 1, LCD output */
    
    do {    /* stay in the loop until it is not busy */
        PTA->PSOR = EN;     /* raise E */
        delayMs(0);
        status = PTD->PDIR; /* read status register */
        PTA->PCOR = EN;
        delayMs(0);			/* clear E */
    } while (status & 0x80);    /* check busy bit */
    
    PTA->PCOR = RW;         /* R/W = 0, LCD input */
    PTD->PDDR = 0xFF;       /* PortD output */
}

void LCD_command(unsigned char command)
{
    LCD_ready();			/* wait until LCD is ready */
    PTA->PCOR = RS | RW;    /* RS = 0, R/W = 0 */
    PTD->PDOR = command;
    PTA->PSOR = EN;         /* pulse E */
    delayMs(0);
    PTA->PCOR = EN;
}

void LCD_command_noWait(unsigned char command)
{
    PTA->PCOR = RS | RW;    /* RS = 0, R/W = 0 */
    PTD->PDOR = command;
    PTA->PSOR = EN;         /* pulse E */
    delayMs(0);
    PTA->PCOR = EN;
}

void LCD_data(unsigned char data)
{
    LCD_ready();			/* wait until LCD is ready */
    PTA->PSOR = RS;         /* RS = 1, R/W = 0 */
    PTA->PCOR = RW;
    PTD->PDOR = data;
    PTA->PSOR = EN;         /* pulse E */
    delayMs(0);
    PTA->PCOR = EN;
}

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