### Project 20 1602 LCD

![](media/image-20251124095334557.png)

**1. Introduction**
In this experiment, we use an Arduino to drive the 1602 LCD.1602 LCD has wide applications. In the beginning,1602 LCD uses a HD44780 controller. Now, almost all 1602 LCD module uses a compatible IC, but their features are basically the same.

**2. 1602LCD Parameters**

- Display Capacity: 16 × 2 characters
- Chip Operating Voltage: 4.5 ~ 5.5V
- Working Current: 2.0mA (5.0V)
- Optimum working voltage of the module is 5.0V
- Character Size: 2.95 * 4.35 (W * H) mm

**3. Pin Description of 1602 LCD**

| No.  | Mark | Pin Description          | No.  | Mark | Pin Description           |
| ---- | ---- | ------------------------ | ---- | ---- | ------------------------- |
| 1    | VSS  | Power GND                | 9    | D2   | Date I/O                  |
| 2    | VDD  | Power Positive           | 10   | D3   | Date I/O                  |
| 3    | VL   | LCD Voltage Bias Signal  | 11   | D4   | Date I/O                  |
| 4    | RS   | Select data/command(V/L) | 12   | D5   | Date I/O                  |
| 5    | R/W  | Select read/write(H/L)   | 13   | D6   | Date I/O                  |
| 6    | E    | Enable Signal            | 14   | D7   | Date I/O                  |
| 7    | D0   | Date I/O                 | 15   | BLA  | Back Light Power Positive |
| 8    | D1   | Date I/O                 | 16   | BLK  | Back Light Power Negative |

**4. Interface Description**

1. two power sources, one for module power, another one for backlight, generally use 5V. In this project, we use 3.3V for backlight.
2. **VL** is the pin for adjusting contrast ratio; it usually connects a potentiometer(no more than 5KΩ) in series for its adjustment.

In this experiment, we use a 1KΩ resistor. For the connection, it has 2 methods, namely high potential and low potential. Here, we use low potential method; connect the resistor and then the GND.

3. **RS** is a very common pin in LCD. It's a selecting pin for command/data. When the pin is in high level, it's in data mode; when it's in low level, it's in command mode.
4. **RW** pin is also very common in LCD. It's a selecting pin for read/write. When the pin is in high level, it's in read operation; when it's in low level, it's in write operation.
5. **E** pin is also very common in LCD. Usually, when the signal in the bus is stabilized, it sends out a positive pulse requiring read operation. When this pin is in high level, the bus is not allowed to have any change.
6. **D0-D7** is 8-bit bidirectional parallel bus, used for command and data transmission.
7. **BLA** is anode for back light; BLK, cathode for back light.

**5. Basic Operations of 1602LCD**

| Read status   | input | RS=L, R/W=H, E=H                              | output | D0-D7=status word |
| ------------- | ----- | --------------------------------------------- | ------ | ----------------- |
| Write command | input | RS=L, R/W=H, D0-D7=command code, E=high pulse | output | none              |
| Read data     | input | RS=H, R/W=H, E=H                              | output | D0-D7=data        |
| Write data    | input | RS=H, R/W=L, D0-D7=data, E=high pulse         | output | none              |

**6. Hardware Required**

- 1 * Controller board
- 1 * 1602 LCD
- 1 * Breadboard
- 1 * potentiometer
- 1 * USB cable
- 16 *Jumper wires

**7. Connection & Sample Program**

1602 can directly communicate with Arduino. According to the product manual, it has two connection methods, namely 8-bit connection and 4-bit connection.

- **8-bit connection method**

![](media/image-20251124095710190.png)

- **Connection for REV4**

![](media/image-20251124095739588.png)

- **Connection for 2560 R3**

![](media/image-20251124095813622.png)

**8. Sample Code A**

```c
int DI = 12;
int RW = 11;
int DB[] = {3, 4, 5, 6, 7, 8, 9, 10};// use array to select pin for bus
int Enable = 2;
void LcdCommandWrite(int value) 
{
    // define all pins
    int i = 0;
    for (i=DB[0]; i <= DI; i++) // assign value for bus
    {
       digitalWrite(i,value & 01);// for 1602 LCD, it uses D7-D0( not D0-D7) for signal identification; here, it’s used for signal inversion. 
       value >>= 1;
    }
    digitalWrite(Enable,LOW);
    delayMicroseconds(1);
    digitalWrite(Enable,HIGH);
    delayMicroseconds(1);  // wait for 1ms
    digitalWrite(Enable,LOW);
    delayMicroseconds(1);  // wait for 1ms
}

void LcdDataWrite(int value) 
{
    // initialize all pins
    int i = 0;
    digitalWrite(DI, HIGH);
    digitalWrite(RW, LOW);
    for (i=DB[0]; i <= DB[7]; i++) 
    {
       digitalWrite(i,value & 01);
       value >>= 1;
	}
    digitalWrite(Enable,LOW);
    delayMicroseconds(1);
    digitalWrite(Enable,HIGH);
    delayMicroseconds(1);
    digitalWrite(Enable,LOW);
    delayMicroseconds(1);  // wait for 1ms
}

void setup (void) 
{
    int i = 0;
    for (i=Enable; i <= DI; i++) 
    {
       pinMode(i,OUTPUT);
    }
    delay(100);
    // initialize LCD after a brief pause
    // for LCD control
    LcdCommandWrite(0x38);  // select as 8-bit interface, 2-line display, 5x7 character size 
    delay(64);                      
    LcdCommandWrite(0x38);  // select as 8-bit interface, 2-line display, 5x7 character size 
    delay(50);                      
    LcdCommandWrite(0x38);  // select as 8-bit interface, 2-line display, 5x7 character size             
    delay(20);                      
    LcdCommandWrite(0x06);  // set input mode
                             // auto-increment, no display of shifting
    delay(20);                      
    LcdCommandWrite(0x0E);  // display setup
                             // turn on the monitor, cursor on, no flickering
    delay(20);                      
    LcdCommandWrite(0x01);  // clear the screen, cursor position returns to 0
    delay(100);                      
    LcdCommandWrite(0x80);  //  display setup
                             //  turn on the monitor, cursor on, no flickering

    delay(20);                      
}

void loop (void) 
{
  LcdCommandWrite(0x01);  // clear the screen, cursor position returns to 0  
  delay(10); 
  LcdCommandWrite(0x80+3); 
  delay(10);                     
  // write in welcome message 
  LcdDataWrite('W');
  LcdDataWrite('e');
  LcdDataWrite('l');
  LcdDataWrite('c');
  LcdDataWrite('o');
  LcdDataWrite('m');

  LcdDataWrite('e');
  LcdDataWrite(' ');
  LcdDataWrite('t');
  LcdDataWrite('o');
  delay(10);
  LcdCommandWrite(0xc0+1);  // set cursor position at second line, second position
  delay(10); 
  LcdDataWrite('g');
  LcdDataWrite('e');
  LcdDataWrite('e');
  LcdDataWrite('k');
  LcdDataWrite('-');
  LcdDataWrite('w');
  LcdDataWrite('o');
  LcdDataWrite('r');
  LcdDataWrite('k');
  LcdDataWrite('s');
  LcdDataWrite('h');
  LcdDataWrite('o');
  LcdDataWrite('p');
  delay(5000);
  LcdCommandWrite(0x01);  // clear the screen, cursor returns to 0  
  delay(10);
  LcdDataWrite('I');
  LcdDataWrite(' ');
  LcdDataWrite('a');
  LcdDataWrite('m');
  LcdDataWrite(' ');
  LcdDataWrite('h');
  LcdDataWrite('o');
  LcdDataWrite('n');
  LcdDataWrite('g');
  LcdDataWrite('y');
  LcdDataWrite('i');
  delay(3000);
  LcdCommandWrite(0x02); // set mode as new characters replay old ones, where there is no new ones remain the same.
  delay(10);
  LcdCommandWrite(0x80+5); // set cursor position at first line, sixth position
  delay(10);  

  LcdDataWrite('t');
  LcdDataWrite('h');
  LcdDataWrite('e');
  LcdDataWrite(' ');
  LcdDataWrite('a');
  LcdDataWrite('d');
  LcdDataWrite('m');
  LcdDataWrite('i');
  LcdDataWrite('n');
  delay(5000);
}
```

![](media/14.png)

**9. 4-bit connection method:**
When using this module, 8-bit connection uses all the digital pins of the Arduino, leaving no pin for sensors. What then? you can use 4-bit connection.

- **Connection for REV4:**

![](media/image-20251124100134076.png)

- **Connection for 2560 R3**

![](media/image-20251124100158186.png)

After the connection, upload below code to the controller board and see how it goes.

**10. Sample Code B**

```c
int LCD1602_RS=12;   
int LCD1602_RW=11;   
int LCD1602_EN=10;   
int DB[] = { 6, 7, 8, 9};
char str1[]="Welcome to";
char str2[]="geek-workshop";
char str3[]="this is the";
char str4[]="4-bit interface";

void LCD_Command_Write(int command)
{
    int i,temp;
    digitalWrite( LCD1602_RS,LOW);
    digitalWrite( LCD1602_RW,LOW);
    digitalWrite( LCD1602_EN,LOW);
    temp=command & 0xf0;
    for (i=DB[0]; i <= 9; i++)
    {
       digitalWrite(i,temp & 0x80);
       temp <<= 1;
    }
    digitalWrite( LCD1602_EN,HIGH);
    delayMicroseconds(1);
    digitalWrite( LCD1602_EN,LOW);
    temp=(command & 0x0f)<<4;
    for (i=DB[0]; i <= 10; i++)
    {
       digitalWrite(i,temp & 0x80);
       temp <<= 1;
    }
    digitalWrite( LCD1602_EN,HIGH);
    delayMicroseconds(1); 
    digitalWrite( LCD1602_EN,LOW);
}

void LCD_Data_Write(int dat)
{
    int i=0,temp;
    digitalWrite( LCD1602_RS,HIGH);
    digitalWrite( LCD1602_RW,LOW);
    digitalWrite( LCD1602_EN,LOW);
    temp=dat & 0xf0;
    for (i=DB[0]; i <= 9; i++)
    {
       digitalWrite(i,temp & 0x80);
       temp <<= 1;
    }
    digitalWrite( LCD1602_EN,HIGH);
    delayMicroseconds(1);
    digitalWrite( LCD1602_EN,LOW);
    temp=(dat & 0x0f)<<4;
    for (i=DB[0]; i <= 10; i++)
    {
       digitalWrite(i,temp & 0x80);
       temp <<= 1;
    }
    digitalWrite( LCD1602_EN,HIGH);
    delayMicroseconds(1); 
    digitalWrite( LCD1602_EN,LOW);
}

void LCD_SET_XY( int x, int y )
{
  int address;
  if (y ==0)    address = 0x80 + x;
  else          address = 0xC0 + x;
  LCD_Command_Write(address); 
}

void LCD_Write_Char( int x,int y,int dat)
{
  LCD_SET_XY( x, y ); 
  LCD_Data_Write(dat);
}

void LCD_Write_String(int X,int Y,char *s)
{
    LCD_SET_XY( X, Y );    // address setup 
    while (*s)             // write character string
    {
      LCD_Data_Write(*s);   
      s ++;
    }
}

void setup (void) 
{
  int i = 0;
  for (i=6; i <= 12; i++) 
   {
     pinMode(i,OUTPUT);
   }
  delay(100);
  LCD_Command_Write(0x28);// 4 wires, 2 lines 5x7
  delay(50); 
  LCD_Command_Write(0x06);
 
 delay(50); 
  LCD_Command_Write(0x0c);
  delay(50); 
  LCD_Command_Write(0x80);
  delay(50); 
  LCD_Command_Write(0x01);
  delay(50); 

}

void loop (void)
{
   LCD_Command_Write(0x01);
   delay(50);
   LCD_Write_String(3,0,str1);// line 1, start at the fourth address
   delay(50);
   LCD_Write_String(1,1,str2);// line 2, start at the second address
   delay(5000);
   LCD_Command_Write(0x01);
   delay(50);
   LCD_Write_String(0,0,str3);
   delay(50);
   LCD_Write_String(0,1,str4);
   delay(5000);
}
```