simple LCD interfacing

16X2 LCD programming for beginners.

I Aim to write a programming 16x2 LCD in simplest language skills using 89C51 IC.

IMPORTANT: I'm not responsible for any short circuit you make or damage you cause to the components. This circuit has been tested well.

Components required: (Note: This costs are with respect to Goan Retail sales).I buy from www.onlinetps.com

1. JHD 162A 16x2 LCD        Approx. Rs.150
2. AT89C51 Microcontroller  Approx. Rs.80
3. 40 Pin ZIP Socket for microcontroller.  Approx. Rs.40
4. Tactile Switch Approx. Rs. 4
5. 41k ohms 1/4Watts resistor Approx Rs. 0.75
6. Electrolytic Capacitors 1uF,10uF both of 25v Rating. Approx. Rs. 6 (3+3)

7. Crystal 11Mhz Approx. Rs.16
8. Two Ceramic capacitors 22pF Approx Rs.1.5 (0.75+0.75)
9. Three 10k ohms Resistors 1/4Watts  Approx. Rs.2.25 (0.75+0.75+0.75)
10. Trim pot 10k ohms Approx. Rs.15
11. 220Ohms Resistor Approx. Rs.0.75
12. epoxy type PCB. (can buy from ebay) Approx. Rs.200 per 30cm sq.
13. External +5V power supply. Approx. Rs. 70 (if you make one using LM7805, Requires 6V or 12V, 500mA transformer as per you)

Let me explain you simple Basics on LCD. This LCD is JHD 162A (datasheet)

Summary on LCD:

LCD means Liquid Crystal Display. Liquid Crystal Polarizes on potential drop across it hence blocking light passing through it.(black pixel). When no potential is dropped the LCD passes light hence white pixel. 

16x2 means 16 columns and 2 rows of alphanumeric ASCII blocks on the LCD.

Has three control signals and one databus. 

R/W: When this signal is '1' = Reads data from the LCD RAM. When this signal is '0' = Writes data on LCD RAM.

EN: Is basically a Latch signal. You have to send '1' first and then '0' signal with a particular delay to latch the data.

RS: Is a Register Select Control signal. When this signal is '1' = It accepts data to be displayed. When this signal is '0' = It accepts instructions for the LCD like setting font, cursor position etc.

D0 to D7: Is 8-bit Databus. It is used to send both data as well as Instructions to the LCD based upon control signals.

Backlight + and Backlight GND: Turns on Backlight of that LCD so that you can see the words correctly.

VEE: is a contrast voltage. Using a trim pot you can adjust the contrast of the LCD. More voltage more the contrast and vice versa(voltage should never exceed VCC = +5 volts).

This LCD has 2 lines and can write maximum 16 letter word per line.

That is all you have to know till now.

Next you should know how to connect a LCD to any microcontroller. For our demonstration I'm using Atmel AT89C51. Check the circuit diagram below for details. Construct this circuit diagram. (Beware wrong connections on LCD or microcontroller can permanently damage the devices).

Thirdly after constructing you should know some basics on C programming of the particular controller. For programming 89C51, you need a programmer. buy options shown here: I use this one , check the link below

89xxx series programmer USB 

You need a keil uVision IDE software (universal compiler  for Atmels and ARMs microcontroller) which will compile your code and give a hex file as output. That hex file has to be programming into the microcontroller.

And main thing is programming the controller. 

There are some instructions you need to know to make lcd work perfectly. If you know this well, programming is piece of cake.

Learn this commands very well.

You will execute this command first after 50msec delay(LCD needs a delay at start before sending commands).

1.    First you Set RS= 0, R/W=0, EN=1; And then write this hex code on data bus given below:

D7	D6	D5	D4	D3	D2	D1	D0
0	0	1	DL	N	F	0	0

Where D7 is Most significant Bit [MSB] and D0 is Least Significant Bit [LSB].

Write 0's and 1's as shown on the bit value but chose the ones which are named DL, N, F

DL means Data Length : If '1' is put on D4 bit then It considers  8-Bit data bus. (Which is what we need exactly to work with. If '0' is put then it considers 4-Bit data bus. And our 8bit data will never be recognized. So choose it wisely.

N means Number of Display lines: You can chose maximum 2 lines since its 16x2 LCD. The internal controller of LCD supports maximum 2 lines for alpha numeric LCD's like this. For 16x4 LCD there are 2 internal controllers. Each supporting 2 lines. So Line mapping is tricky there.

On 16x2 LCD: when '1' is put in place of N , 2 lines are selected for use. When '0' you can use only 1 line for displaying data.

F means Font size. when  '1' is put it displays 5x7 pixel font. When '0' is put it displays 5x10 pixel font.

And main thing. When you send this data on the databus of LCD. You have to latch using EN signal 4times. With overall delay atleast  greater than 30 milli seconds.

If you send this instruction below: your hex code will be 0x38. Eg.

D7	D6	D5	D4	D3	D2	D1	D0
0	0	1	1	1	0	0	0

This instruction will Enable 8-bit Databus, Set 2 lines, and Select font size 5x7.

For next, You have to execute this instruction.

D7	D6	D5	D4	D3	D2	D1	D0
0	0	0	0	1	D	C	B

D means Display On/Off Select: If you  put  '1' you will see the characters on screen.  If you put '0' you will never see characters on the screen.

C means Cursor On/ Off select: If you put '1' you will see the cursor on the screen hence showing you present location where you next data will be displayed. If you put '0' the cursor will be hidden and your present location will be hoax(doesn't matter for professional programmer).

B means blinking of Cursor: If you put '1' your cursor will blink. If you put '0' it will not blink. This instruction will not work if cursor is turned OFF.

It requires only 1 Latch enable.

If you send this instruction below: hex code = 0x0F

D7	D6	D5	D4	D3	D2	D1	D0
0	0	0	0	1	1	1	1

It will display the characters, will display the cursor and it will blink.

How do I clear the Display after writing characters I want????

It requires only 1 Latch Enable.

Well use this instruction below: hex code = 0x01;

D7	D6	D5	D4	D3	D2	D1	D0
0	0	0	0	0	0	0	1

This code will clear the entire display. And bring your cursor to position 0. Or home position.

How to write on a particular line????

Use this instruction to select line 1: hex code 0x80

D7	D6	D5	D4	D3	D2	D1	D0
1	0	0	0	0	0	0	0

Use this instruction to select line 2: hex code 0xC0

D7	D6	D5	D4	D3	D2	D1	D0
1	1	0	0	0	0	0	0

There is also instruction to shift the cursor left and right for Displaying data at particular location on the LCD.
You can check the datasheet of the LCD for mode advanced codes if you want to explore more.

To display Data on LCD, You have to Change RS=1 after executing above instructions.

For Ascii codes. Follow the table below: 

Display the ascii table here for LCD: For example M =0100 1101 = 0x4D on this LCD Character RAM.

Now I will give you the code I wrote to display my name on JHD 162A.

If you followed the instructions I wrote above. You will understand each and every line i write here.

Type this code below in bold black on your c compiler(keil uVision 3):

#include "REGX51.H" //It contains all the Register, Special register addressing information

//Go into REGX51.H if you want to see deep details on 89C51 architecture.

#define RW P0_1 //This is simple way to assign names to Port Pins; RW is named as Port 0 Bit 1

#define RS P0_0 //RS is named  for Port 0 Bit 0

#define EN P0_2 //EN is named for Port0 Bit 2

#define DATA P2 //DATA bus is named for Port 2 (8-bit)

void delay(int n); //universal Delay routine for your code; can be customised for your use.

void s_inst(void); //Send Instruction Function Select routine

void s_data(void); //Send Data Select routine

void s_latch(void); // Latch Data/Instruction on LCD Databus.

void main(void) //Main function

{

int k=0;

char x[6]="Macjan"; //you can name it whatever you want.

char y[9]="Fernandes"; //You can name it whatever you want.

             RS=0;  //Initialize RS=0 for selecting instruction Send

             RW=0; //Select RW=0 to write Instruction/data on LCD

             EN=1; //EN=1 for unlatch. (used at initial condition)

             delay(100000); //some LCDs takes time to initialize at startup

             s_inst(); //Call Instruction Select routine

             DATA=0X38; //Send This instruction on Databus Port 2 on LCD databus.

             s_latch(); //Latch this above instruction 4 times

             s_latch();

             s_latch();

             s_latch();

             DATA=0X0F;// Send Second Instruction on Port 2.

             s_latch();

             DATA=0X10; // Set cursor on line 1. Use 0xC0 to write on line 2.

             s_latch(); //Latch the above instruction 1 time.

             DATA=0X0; //Before changing to write data select. Make port 2 =0x0 so that LCD receives nothing

             s_data(); //Change the input type to Data.(before it was instruction input)

             s_latch();  //Latch the above instruction once.

             for(k=0;k<=5;k++)

             {

                         DATA=x[k];  //It will send x[0]='M' as = 0x4D on Port 2.

                         s_latch(); //Latch the above instruction only once. Or it will clone each character twice if you latch twice.

             }

//to type on line 2 call instruction routine first then send instruction on port 2.

            s_inst(); //Instruction Select routine called

            DATA=0XC0; // Set cursor on line 2. Use 0x10 to write on line 1.

            s_latch();

            DATA=0X0; //Before changing to write data select. Make port 2 =0x0 so that LCD receives nothing

            s_data(); //Change the input type to Data.(before it was instruction input)

            //Now it will show Fernandes on line 2.

            for(k=0;k<=8;k++)

             {

                         DATA=y[k];  //It will send y[0]='F' as = 0x45 on Port 2.

                         s_latch(); //Latch the above instruction only once. Or it will clone each character twice if you latch twice.

             }

             while(1); //infinite loop after completing task

}

void delay(int n) //Universal delay routine

{

 int i=0,j=0;

 for(i=0;i<=n;i++)

 for(j=0;j<=10;j++);

}

void s_inst(void) //Instruction select routine

{

             RS=0;

             RW=0;

}

void s_data(void) // Data select routine

{

            RS=1;

            RW=0;

}

void s_latch(void) // Latch routine

{

            EN=1;

            delay(1000);

            EN=0;

            delay(1000);

}

// END of program

 Now how to make a custom character?

This is how a character looks on LCD. There are 8Rows (b0 to b7) and 5Columns (d0 to d4). 

I did a example here to show you smiley called Smile on the character map. The black pixels means On (1) pixels.

And the pixels which are not On are  (0) pixels. So on the right side I have shown you the hex representation of a row.

Well to enter a character in a LCD. You must know the CGRAM AD instruction. Well the below table is the CGRAM Instruction.

First you Set RS= 0, R/W=0, EN=1; And then write this hex code on data bus given below:

D7	D6	D5	D4	D3	D2	D1	D0
0	1	Ad5	Ad4	Ad3	Ad2	Ad1	Ad0

Where Ad0 to Ad5 are address to the CGRAM.

Well Usually we put the address as 0x000000 in this locations.

Hence it gives hex value as = 0x40; (0x0100 0000)

If you send this code as instruction, and then latch it once.

The LCD will wait for 8byte data for the character.

So you have to send this 8bytes as one byte latched at a time.

After completion of 8 bytes transfer in data mode, the LCD will consider you have stored the character temporarily. And hence you clear screen the LCD using command 0x01.

The LCD has 16 CGRAM registers. You can store 16 Characters. I will show you simple example to display smiley using above circuit.

#include "REGX51.H"

#define RW P0_1
#define RS P0_0
#define EN P0_2
#define DATA P2

void delay(int n);
void s_inst(void);
void s_data(void);
void s_latch(void);
void custom_character(char x[64]);//custom character function

void main(void) //Main function
{

             char smile[8]={0x00,0x00,0x0A,0x00,0x11,0x0E,0x00,0x00}; //This is taken from the above picture pixel  hex representation
             RS=0; 
             RW=0;
             EN=1;
             delay(100000);
             s_inst();
             DATA=0X38;
             s_latch();
             s_latch();
             s_latch();
             s_latch();
             DATA=0X0f;
             s_latch();
             DATA=0X10;
             s_latch();
             DATA=0X01;   
             s_latch();
             custom_character(smile);
                  DATA=0x00; //ASCII address equivalent for your smile character. for next character it will be 0x01, 0x02,0x03,0x04,0x05,0x06,0x07.   
             //for displaying next custom characters you have to utilize the full array i mentioned in custom character.
             //Remember you can write there only once. If you modify your old ones, the screen will get modified too.
             s_latch();

             while(1); //infinite loop after completing task
}



void custom_character(char x[64])
{
int k;
            s_inst();
            DATA=0x40; //Send the instruction to set CGRAM address to store your custom character.
            s_latch(); //Latch this data once.
            s_data();//Enable data mode.
    //Next you have to send 8bytes of character data. Do like this below.

        for(k=0;k<=63;k++)
        {
            DATA=x[k];
            s_latch();
            }
        //After 8 bytes transfer you must run a clear screen once, I am having issues in reading data here, so i used this instruction to overcome.
        s_inst();
        DATA=0x01;
        s_latch();
        s_data();
 }

 void delay(int n) //Universal delay routine
{
 int i=0,j=0;
 for(i=0;i<=n;i++)
 for(j=0;j<=10;j++);
}

void s_inst(void) //Instruction select routine
{
             RS=0;
             RW=0;
}
void s_data(void) // Data select routine
{
            RS=1;
            RW=0;
}
void s_latch(void) // Latch routine
{
            EN=1;
            delay(100);
            EN=0;
            delay(100);
            EN=1;
            delay(100);
}
// END of program

After writing the Code, Do this keil settings:

Menu -> Project -> option for Target1

In device tab select Device Atmen -> AT89C51

In target tab edit 11Mhz Clock. Tick on On-Chip Rom.

In output Tab  tick on Create Hex.