LCD display using PIC

Many device sometime using LED to display the output that had been process by micro-controller etc. LCD display quite famous output display for project that need to display some valid data or represent something for user reference. There is so many type of LCD today. Below is example of LCD type:

128x64

16x2

320x240 QVGA

  

16x1

There are so much brand in market. The famous one brand among students in university is Hitachi 16x2 Alphanumeric LCD module (refer specification). It can show display 16 bit output with 2 row which is equal to 32 bit in real time. We cannot just connect LCD to micro-controller because every each pin have the reserved function based on data sheet. Below is example pin configuration for 16x2 LCD module:
   

Pin	Symbol	Description
1	VSS	Ground
2	VDD	+5V Power Supply
3	VEE	Contrast Adjustment
4	RS	0: Command Register 1: Data register
5	RW	0: Write 1:Read
6	E	Enable
7-14	D0-D8	Data bus
15	LED+	Backlight Positive Power Supply
16	LED-	Backlight Ground

 Table 1: Pin configuration

For circuit connection LCD to micro-controller has shown below: 

 

Figure : LCD module connection

 As we can see, VSS is going for ground, VDD to +5V and VEE to contrast adjustment. Here we using variable resistor, so we can adjust how much brightness that we want. Other pin is refer to coding that we want to program. Some person say that pin D0-D7 should connect to port D on micro-controller, but exactly we can put it on port where we want. All this depends on our programming, whether we declare the variable at port C, port D or else.  

Ok, lets move on to the programming method. Now is the part that need to understand carefully. Here the step before start the programming:

1. Determine which port your want to use to connect with pin D0-D7 and RS, RW and E on LCD module. 
2.  Connect circuit like picture above (except port that you have determine in step 1).
3. Turn on power and see whether the LCD is function or not. 
4. If ok, go to step programming.
5. Open MPLAB, and write programming.

Now we will do some programming for send text on LCD display. It quite tricky actually if you don't know the basic.

LCD Progamming

To program the LCD with micro-controller is little bit tricky. You must need to read the datasheet and must know your compiler. Different compiler different style. Here i'm using C18 compiler since my previous project is using PIC18F family. Below show the simple programming for LCD with PIC:


/*Header******************************************************/

// LCD module connections
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;
sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;
sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
// End LCD module connections

unsigned char ch;                    //
unsigned int adc_rd;                 // Declare variables
char *text;                          //
long tlong;                          //

void main() {
    INTCON = 0;                      // All interrupts disabled
    ANSEL = 0x04;                    // Pin RA2 is configured as an analog input
    TRISA = 0x04;
    ANSELH = 0;                      // Rest of pins are configured as digital
   
    Lcd_Init();                      // LCD display initialization
    Lcd_Cmd(_LCD_CURSOR_OFF);        // LCD command (cursor off)
    Lcd_Cmd(_LCD_CLEAR);             // LCD command (clear LCD)
   
    text = "mikroElektronika";       // Define the first message
    Lcd_Out(1,1,text);               // Write the first message in the first line
    text = "LCD example";            // Define the second message
    Lcd_Out(2,1,text);               // Define the first message
   
    ADCON1 = 0x82;                   // A/D voltage reference is VCC
    TRISA = 0xFF;                    // All port A pins are configured as inputs
    Delay_ms(2000);
   
    text = "voltage:";               // Define the third message
   
    while (1) {
        adc_rd = ADC_Read(2);        // A/D conversion. Pin RA2 is an input.
        Lcd_Out(2,1,text);           // Write result in the second line
        tlong = (long)adc_rd * 5000; // Convert the result in millivolts
        tlong = tlong / 1023;        // 0..1023 -> 0-5000mV
        ch = tlong / 1000;           // Extract volts (thousands of millivolts)
                                     // from result
        Lcd_Chr(2,9,48+ch);          // Write result in ASCII format
        Lcd_Chr_CP('.');
        ch = (tlong / 100) % 10;     // Extract hundreds of millivolts
        Lcd_Chr_CP(48+ch);           // Write result in ASCII format
        ch = (tlong / 10) % 10;      // Extract tens of millivolts
        Lcd_Chr_CP(48+ch);           // Write result in ASCII format
        ch = tlong % 10;             // Extract digits for millivolts
        Lcd_Chr_CP(48+ch);           // Write result in ASCII format
        Lcd_Chr_CP('V');
        Delay_ms(1);
    }
}


*source from mikroElektronika website.

Programming LCD screen is not simple as it look. We need to study a little bit about LCD background which can find in datasheet/ catalog and as a result practice make perfect.