4 bit interfacing of a 16X2 LCD display to PIC16F877A, Atmega16/32, MSP430 & Stellaris launchpad

16x2 LCDs are most commonly used display units in microcontroller based projects. I got much information about LCD, LCD commands, LCD initialization etc from the below link and I hope, it will be very much helpful for beginners.


 




http://www.dinceraydin.com/lcd/intro.htm
Below is my final working code for 4 bit mode LCD with PIC16F877A: (HI-TECH C)

#include<pic.h>
#define _XTAL_FREQ 20e6
__CONFIG(0x3F3A);
#define RS RB2
#define EN RB1
#define databits PORTD
/*----------------PIC INITIALIZATION------------*/
void pic_init()
{
    TRISB2 = 0;
    TRISB1 = 0;
    TRISD = 0;
}

/*-------------LCD FUNCTIONS BEGIN--------------*/
void LCD_STROBE(void)
{
    EN = 1;
    __delay_us(1);
    EN = 0;
}

void data(unsigned char c)
{
    RS = 1;
    __delay_us(50);
    databits = (c >> 4);
    LCD_STROBE();
    databits = (c);
    LCD_STROBE();
}

void cmd(unsigned char c)
{
    RS = 0;
    __delay_us(50);
    databits = (c >> 4);
    LCD_STROBE();
    databits = (c);
    LCD_STROBE();
}

void clear(void)
{
    cmd(0x01);
    __delay_ms(2);
}

void lcd_init()
{
    __delay_ms(15);
    cmd(0x38);
    __delay_ms(1);
    cmd(0x38);
    __delay_us(100);
    cmd(0x38);
    cmd(0x28);            // Function set (4-bit interface, 2 lines, 5*7Pixels)
    cmd(0x28);            // Function set (4-bit interface, 2 lines, 5*7Pixels)
    cmd(0x0c);            // Make cursorinvisible
    clear();            // Clear screen
    cmd(0x6);            // Set entry Mode(auto increment of cursor)
}

void string(const char *q)
{
    while (*q) {
        data(*q++);
    }
}

/*-------------LCD END--------------------*/

main()
{
    __delay_ms(50);
    pic_init();
    lcd_init();
    TRISC = 0;
    while (1) {
        cmd(0x80);
        string("HELLO WORLD");
        cmd(0xc0);
        string("IT IS WORKING:-)");
        
    }
}

                                                                                                                                                     

                            

 

Connections:

-------------------------------------

LCD                  |          PIC      |

-------------------------------------

 Register Select      -->RB2      |

 Enable                  -->RB1       |

-------------------------------------

 D4                       -->RD0        |

 D5                       -->RD1        |

 D6                       -->RD2        |

 D7                       -->RD3        |

-------------------------------------

CLOCK: 20MHz crystal oscillator 

                Also, any other frequency <20MHz could be used. But we need to edit the below line:

#define _XTAL_FREQ 20e6

POT                   -->  4.7k

16x2 LCD WITH AVR (ATMEGA16 or ATMEGA32) - 4 bit mode

#include<avr/io.h>
#define F_CPU 12e6
#include <util/delay.h>

#define RS 6 //PD6
#define EN 7 //PD7
#define databits PORTC //lower nibble
#define LINE1 cmd(0x80)
#define LINE2 cmd(0xc0)

void port_init()
{
    DDRC = 0xff;
    DDRD = (1 << RS)|(1 << EN);
}

void LCD_STROBE(void)
{
    PORTD |= (1 << EN);
    _delay_us(1);
    PORTD &= ~(1 << EN);
}

void data(unsigned char c)
{
    PORTD |= (1 << RS);
    _delay_us(50);
    databits = (c >> 4);
    LCD_STROBE();
    databits = (c);
    LCD_STROBE();
}

void cmd(unsigned char c)
{
    PORTD &= ~(1 << RS);
    _delay_us(50);
    databits = (c >> 4);
    LCD_STROBE();
    databits = (c);
    LCD_STROBE();
}

void clear(void)
{
    cmd(0x01);
    _delay_ms(5);
}

void lcd_init()
{
    _delay_ms(15);
    cmd(0x30);
    _delay_ms(1);
    cmd(0x30);
    _delay_us(100);
    cmd(0x30);
    cmd(0x28);            // Function set (4-bit interface, 2 lines, 5*7Pixels)
    cmd(0x28);            // Function set (4-bit interface, 2 lines, 5*7Pixels)
    cmd(0x0c);            // Make cursorinvisible
    clear();            // Clear screen
    cmd(0x6);            // Set entry Mode(auto increment of cursor)
}

void string(char *p)
{
    while(*p) data(*p++);
}

int main()
{
    _delay_ms(50);
    port_init();
    lcd_init();
    LINE1;
    string("HELLO WORLD");
    LINE2;
    string("IT IS WORKING:-)");
    while(1);
    return 0;
} 

The above code is for AVR microcontroller. I am usign avr-gcc in linux.
Note:
Some bits of PORTC will be used for JTAG , which is JTAG enabled by default. So it may not work as normal IO pin if we didn't disable it in fuse bits. (HFUSE)

Now, the connections are not to be much explained since all is understood from the #defines in the above code.....

To compile it using avr-gcc(linux) and to burn it using usbasp, the command line are as follows:

avr-gcc -mmcu=atmega16 -Os lcd.c

now we get a.out (elf)

to convert it to hex, 

avr-objcopy -j .text -j .data -O ihex a.out a.hex

Now we get a.hex file.

To burn it to atmega16 using usbasp (ISP programmer),

sudo avrdude -p m16 -c usbasp -e -U flash:w:a.hex:i

(for more details, read man page of avrdude, ie "man avrdude")

We can create a make file for the above purpose:

Makefile:

# AVR-GCC Makefile
PROJECT=lcd
SOURCES=lcd.c
CC=avr-gcc
OBJCOPY=avr-objcopy
MMCU=atmega16

CFLAGS=-mmcu=$(MMCU)

$(PROJECT).hex: $(PROJECT).out
    $(OBJCOPY) -j .text -j .data -O ihex $(PROJECT).out $(PROJECT).hex

$(PROJECT).out: $(SOURCES)
    $(CC) $(CFLAGS) -Os -I./ -o $(PROJECT).out $(SOURCES)

program: $(PROJECT).hex
    avrdude -p m16 -c usbasp -U flash:w:$(PROJECT).hex:i
clean:
    rm -f $(PROJECT).out
    rm -f $(PROJECT).hex

type make to build lcd.hex
type sudo make program to load it to avr






------------------------------------------------------------------------------------------------------------------------------------

16x2 LCD WITH MSP430 LAUNCHPAD (4BIT MODE)
 MSP430G2231)

Since the launchpad works at 3.6v, we need to provide an external 5v supply to
power the LCD module. But we can directly connect the port bits of MSP430 to LCD..
Note:

• Never forget to provide a connection between both the grounds of launchpad and external supply.
• Never connect the Vcc of MSP430 to any where on the LCD
• Ground the R/W pin of LCD
• Pull down the VEE of LCD with a 1K resistor or use a POT ..
• Use a 470 ohm resistor to provide the supply for the backlight LED..

C Program:

/*
*MSP430 launchpad based 4bit lcd code..
*Assuming the clock is 1MHz..
*All delays are designed according to that...
*for eg: __delay_cycles(1000) => 1ms delay at 1MHz clock
*Otherwise use any delay routines, if available.
*Note:
In my previous codes, the initialization is not so perfect
because I deviated from the original specifications...
But those codes are at least working for me,, Any way,
now I am providing a better code which includes a
pseudo_8bit_cmd function since the LCD expects an 8 bit 
command at first, before entering to 4 bit mode...

-Connections:
RS -> P1.0
EN -> P1.1
D7 to D4  -> P1.7 to P1.4
R/W to GROUND

-Compiler used: msp430-gcc
-Command line: msp430-gcc -mmcu=msp430g2231 lcd.c -mdisable-watchdog
-Burning code: sudo mspdebug rf2500
> prog a.out
> run

*/

#include<msp430g2231.h>

#define RS(X)     P1OUT = ((P1OUT & ~(BIT0)) | (X))
#define EN(X)   P1OUT = ((P1OUT & ~(BIT1)) | (X<<1))
#define LCD_STROBE do{EN(1);EN(0);}while(0)
#define databits P1OUT  // P1.7 - D7, ....., P1.4 - D4
#define LINE1 cmd(0x80)
#define LINE2 cmd(0xc0)

void port_init()
{
    P1OUT = 0 ;
    P1DIR = 0xff;
}

void data(unsigned char c)
{
    RS(1);
    __delay_cycles(40);  //40 us delay
    databits = (databits & 0x0f) | (c & 0xf0);
    LCD_STROBE;
    databits = (databits & 0x0f) | (c << 4) ;
    LCD_STROBE;
}

void cmd(unsigned char c)
{
    RS(0);
    __delay_cycles(40); //40 us delay
    databits = (databits & 0x0f) | (c & 0xf0);
    LCD_STROBE;
    databits = (databits & 0x0f) | (c << 4) ;
    LCD_STROBE;
}

void pseudo_8bit_cmd(unsigned char c)
{
    RS(0);
    __delay_cycles(15000); //15 ms delay
    databits = (c & 0xf0);
    LCD_STROBE;
}
void clear(void)
{
    cmd(0x01);
    __delay_cycles(3000); //3 ms delay
}

void lcd_init()
{
    pseudo_8bit_cmd(0x30); //this command is like 8 bit mode command
    pseudo_8bit_cmd(0x30); //lcd expect 8bit mode commands at first
    pseudo_8bit_cmd(0x30); //for more details, check any 16x2 lcd spec
    pseudo_8bit_cmd(0x20);
    cmd(0x28);             //4 bit mode command started, set two line
    cmd(0x0c);             // Make cursorinvisible
    clear();               // Clear screen
    cmd(0x6);              // Set entry Mode(auto increment of cursor)
}

void string(char *p)
{
    while(*p) data(*p++);
}

int main()
{
    port_init();
    lcd_init();
    LINE1;
    string("WELCOME TO");
    LINE2;
    string("MSP430 LAUNCHPAD");
    while(1);
}

HEX

 
:10F8000031408002B240805A20013F4000000F93F7
:10F8100005242F839F4F82FA0002FB233F40000004
:10F820000F9304241F83CF430002FC23044124537D
:10F83000B240805A2001B0126AF8B012F2F97F404B
:10F8400080FFB01204F93F4064FAB01238FA7F40EA
:10F85000C0FFB01204F93F406FFAB01238FAFF3F10
:10F8600032D0F000FD3F304080FA041204412453AE
:10F87000C2432100F24322003441304104120441CA
:10F8800024532183C44FFCFF5F4221005FD3C24F4A
:10F890002100034303433F400C001F83FE235F42CC
:10F8A00021004E4F7EF00F005F44FCFF7FF0F0FF21
:10F8B0004FDEC24F21005F4221006FD3C24F2100B3
:10F8C0005F4221007FF0FDFFC24F21005F42210017
:10F8D0004E4F7EF00F005F44FCFF0F5F0F5F0F5F26
:10F8E0000F5F4FDEC24F21005F4221006FD3C24F36
:10F8F00021005F4221007FF0FDFFC24F2100215314
:10F90000344130410412044124532183C44FFCFF8D
:10F910005F4221007FF0FEFFC24F210003430343FB
:10F920003F400C001F83FE235F4221004E4F7EF0BC
:10F930000F005F44FCFF7FF0F0FF4FDEC24F21005D
:10F940005F4221006FD3C24F21005F4221007FF050
:10F95000FDFFC24F21005F4221004E4F7EF00F009D
:10F960005F44FCFF0F5F0F5F0F5F0F5F4FDEC24F03
:10F9700021005F4221006FD3C24F21005F4221006E
:10F980007FF0FDFFC24F210021533441304104126A
:10F99000044124532183C44FFCFF5F4221007FF0C8
:10F9A000FEFFC24F210003433F4087131F83FE2306
:10F9B0005F44FCFF7FF0F0FFC24F21005F42210057
:10F9C0006FD3C24F21005F4221007FF0FDFFC24F85
:10F9D00021002153344130410412044124535F4338
:10F9E000B01204F903433F40E7031F83FE23344171
:10F9F00030410412044124537F403000B0128EF98C
:10FA00007F403000B0128EF97F403000B0128EF986
:10FA10007F402000B0128EF97F402800B01204F918
:10FA20007F400C00B01204F9B012D8F97F400600F4
:10FA3000B01204F9344130410412044124532183AB
:10FA4000844FFCFF073C1F44FCFF6F4F9453FCFFA7
:10FA5000B0127CF81F44FCFF6F4F4F93F4232153E7
:10FA60003441304157454C434F4D4520544F004D94
:10FA70005350343330204C41554E4348504144009C
:02FA8000001371
:040000030000F80001
:00000001FF

16x2 LCD with STELLARIS LAUNCHPAD:

Here is the final working  lcd code for stellaris launchpad. Main source file is embedded below but it requires linker script, startup code and many headers so I am posting the link towards my git repo which have complete files required for all stellaris codes. If you have any doubt, u can ask by comments...

 Here is a working code for stellaris launchpad.
https://github.com/vinodstanur/stellaris-launchpad