/* www.MicroDigitalEd.com
 * p3_3.c: Initialize and display "hello" on the LCD using 4-bit data mode.
 * Data and control pins share Port 4.
 * 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 among the LCD modules.
 * You may want to adjust the amount of delay for your LCD controller. 
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */
#include "msp.h"

#define RS 1     /* P4.0 mask */ 
#define RW 2     /* P4.1 mask */ 
#define EN 4     /* P4.2 mask */

void delayMs(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(0x80);  /* set cursor at beginning of first line */
        LCD_data('h');      /* write the word "Hello" */
        LCD_data('e');
        LCD_data('l');
        LCD_data('l');
        LCD_data('o');
        delayMs(500);
    }
}

void LCD_init(void) {
    P4->DIR = 0xFF;     /* make P4 pins output for data and controls */
    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 after each char */
    LCD_command(0x01);      /* clear screen, move cursor to home */
    LCD_command(0x0F);      /* turn on display, cursor blinking */
}

/* With 4-bit mode, each command or data is sent twice with upper 
 * nibble first then lower nibble.
 */
void LCD_nibble_write(unsigned char data, unsigned char control) {
    data &= 0xF0;           /* clear lower nibble for control */
    control &= 0x0F;        /* clear upper nibble for data */
    P4->OUT = data | control;       /* RS = 0, R/W = 0 */
    P4->OUT = data | control | EN;  /* pulse E */
    delayMs(0);
    P4->OUT = data;                 /* clear E */
    P4->OUT = 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 milliseconds when system clock is at 3 MHz */
void delayMs(int n) {
    int i, j;
    
    for (j = 0; j < n; j++)
        for (i = 250; i > 0; i--);      /* Delay */
}