HD44780-compatible LCD Driver for LPC2148

lcd.c

/*
 * lcd.c
 *
 * Low-level driver for Hitachi's HD44780 LCD for LPC2148 board
 *
 *  Created on: 20-Jan-2014
 *      Author: Shrikant Giridhar
 */

#include "lpc214x.h"

// LCD Pinout
#define DATA	19	// Parallel port (4 pins)
#define ENABLE	18	// Enable
#define RS	17	// Register Select - Data/Command (0 or 1)
#define RW	16	// Write/Read select (0 or 1)
#define BUSY	22	// Busy flag (DB7)

// HD44780U command set
#define _CLEAR	0x01	// Clear DDRAM
#define	_FNSET	0x28	// 4-bit, 2-line and 5x8 fonts
#define _ENTRY	0x03	// Increment cursor, no display shift
#define _HOME	0x80	// Beginning of DDRAM
#define _CMD	0x00	// Send a command
#define _TEXT	0x01	// Send data

// Useful Macros
#define	_BV(x)		1 << x
#define TOGGLE(x)	x ^= x

// Prototypes
void initLCD(void);
void cmdLCD(uint32_t cmd);
void putLCD(unsigned char character);
void print(char* str);
void clrscr(void);

static void writeLCD(uint32_t cmd);
static void tinyDelay(void);

/*! \brief Generate a cycle-accurate delay */
static void tinyDelay(void)
{
	// Adhoc; convert to asm later

	uint32_t i = 0;
	for ( ; i < 131072; ++i);

}

/*! \brief Send commands to the LCD */
static void writeLCD(uint32_t data, uint32_t rs)
{
	// Prepare for write
	IO0CLR |= _BV(ENABLE);
	IO0CLR |= _BV(RW);
	if (rs)
		IO0CLR |= _BV(RS);
	else
		IO0SET |= _BV(RS);

	// Send upper nibble (MSB)
	IO0PIN = (data & 0xF0) << DATA;

	IO0PIN ^= _BV(ENABLE);
	IO0PIN ^= _BV(ENABLE);

	// Send lower nibble (LSB)
	IO0PIN = (data & 0x0F) << DATA;

	// Strobe
	IO0PIN ^= _BV(ENABLE);
	IO0PIN ^= _BV(ENABLE);

	// See if write is done
	while(IO0PIN & _BV(BUSY));

	tinyDelay();

	// Set all (inactive)
	IO0SET |= 0x0F << DATA;

}

/*! \brief Clear the display */
void clrscr(void)
{
	tinyDelay();
	writeLCD(_CLEAR);
}


/*! \brief Send an instruction to the LCD controller */
void cmdLCD(uint32_t cmd)
{
	tinyDelay();
	writeLCD(cmd, _CMD);
}


/*! \brief Display a single character on the LCD */
void putLCD(unsigned char character)
{
	tinyDelay();
	writeLCD(character, _TEXT);
}


/*! \brief Sets up the LCD for communication */
void initLCD(void)
{
	// All outputs
	IO0DIR |= (0x0F << DATA) | (_BV(ENABLE)) | (_BV(RW)) | (_BV(RS));

	cmdLCD(_CLEAR);
	cmdLCD(_FNSET);
	cmdLCD(_ENTRY);
	cmdLCD(_HOME);

}


/*! \brief Prints a formatted string on the LCD */
void print(char *str)
{
	// Save context
	char *temp;
	temp = str;
	while (*temp != '\0')
	{
		putLCD(*temp);
		++temp;
	}
	putLCD('\n');

}

Example Usage:

print("Hello World");    // Appends newline automatically
clrscr();