1 liquid crystal display principle
The principle of liquid crystal display is to use the physical characteristics of liquid crystal to control the display area by voltage, and display when there is electricity, so that the figure can be displayed. The liquid crystal display has the characteristics of thin thickness, direct driving for large-scale integrated circuits, and easy realization of full-color display, and has been widely used in many fields such as portable computers, digital cameras, and PDA mobile communication tools.
2 classification of liquid crystal displays
There are many types of liquid crystal display classification methods, which can be divided into segment type, character type, dot matrix type and the like according to the display manner. In addition to the black and white display, the liquid crystal display has a multi-gradation color display. If divided according to the driving method, it can be divided into static driving (StaTIc), simple matrix driving (Simple Matrix) and active matrix driving (AcTIve Matrix).
3 LCD display various graphics display principle:
Line segment display
The dot matrix liquid crystal is composed of M&TImes; N display units, assuming that the LCD display has 64 rows, each row has 128 columns, and each of the 8 columns corresponds to 1 byte of 8 bits, that is, each row consists of 16 bytes, a total of 16 & TImes; 8 = 128 points, 64 × 16 display units on the screen correspond to 1024 bytes of the display RAM area, and the content of each byte corresponds to the light and dark of the corresponding position on the display screen. For example, the light and dark of the first line of the screen is determined by the 16-byte content of 000H-00FH in the RAM area. When (000H)=FFH, a short bright line is displayed in the upper left corner of the screen, and the length is 8 points. When (3FFH)=FFH, a short bright line is displayed in the lower right corner of the screen; when (000H)=FFH, (001H)=00H, (002H)=00H,...(00EH)=00H,(00FH)= At 00H, a dotted line consisting of 8 bright lines and 8 dark lines is displayed at the top of the screen. This is the basic principle of LCD display.
Character display
Displaying a character with the LCD is more complicated, because a character consists of a 6×8 or 8×8 dot matrix, and it is necessary to find and display 8 bytes of the display RAM area corresponding to certain positions on the screen, and to make each word The different bits of the section are "1", the others are "0", the lighting of "1", and the "0" is not lit. This will form a character. However, because the controller with the character generator is simple, the display character is relatively simple, and the controller can be operated in the text mode. According to the row and column number displayed on the LCD and the number of columns in each row, the corresponding display RAM is found. Address, set the cursor, send the code corresponding to the character here.
Display of Chinese characters
The display of Chinese characters is generally in the form of graphics. The dot matrix code of the Chinese characters to be displayed is extracted from the microcomputer in advance (usually using the font extraction software). Each Chinese character accounts for 32B, and the left and right halves are each 16B, and the left side is 1, 3 5, the right side is 2, 4, 6... According to the row and column number displayed on the LCD and the number of columns in each row, the address corresponding to the display RAM can be found, the cursor is set, and the first character of the Chinese character to be displayed is sent. Section, the cursor position is incremented by 1, the second byte is sent, the newline is aligned by column, and the third byte is sent... until 32B is displayed, a complete Chinese character can be obtained on the LCD.
1602LCD main technical parameters:
Display capacity: 16 × 2 characters
Chip working voltage: 4.5-5.5V
Working current: 2.0mA (5.0V)
Module best working voltage: 5.0V
Character size: 2.95 × 4.35 (W × H) mm
Pin description
Pin 1: VSS is the ground power.
Pin 2: VDD is connected to 5V positive power supply.
Pin 3: VL is the LCD contrast adjustment end. When the positive power is connected, the contrast is the weakest. When the grounding is the highest, the contrast is too high. When the contrast is too high, “ghosting†will occur. When using it, the contrast can be adjusted by a 10K potentiometer.
　　 Pin 4: RS is the register selection. When the high level is selected, the data register is selected, and when the low level is selected, the instruction register is selected.
　　 Pin 5: R/W is the read/write signal line. When it is high, it performs a read operation, and when it is low, it performs a write operation. When RS and R/W are low together, the instruction or display address can be written. When RS is low, R/W is high, the busy signal can be read. When RS is high, R/W is low. Data can be written.
Pin 6: The E terminal is the enable terminal. When the E terminal changes from a high level to a low level, the liquid crystal module executes the command.
　　 Pins 7 to 14: D0 to D7 are 8-bit bidirectional data lines.
　　 Pin 15: The backlight is positive.
　　 Pin 16: Backlight negative.
#include 《reg51.h》
#define uchar unsigned char
#define uint unsigned int
Sbit LCD_E=P3^5; //Define the interface
Sbit LCD_RW=P3^6;
Sbit LCD_RS=P3^7;
#define LCD_Data P1 //Data Interface
Uchar up[]={"IvU,hupeixian"};
Uchar code down[]={"_by fu â€}
/*************************Time delay function********************* ********/
Void Delay_ms(uint time)
{
Uint i,j;
For(i = 0;i " time;i ++)
For(j = 0;j " 930;j ++);
}
/**********************Detection status************************* ***********/
Uchar LCD_ReadStatus(void)
{
LCD_Data = 0xFF;
LCD_RS = 0;
LCD_RW = 1;
LCD_E = 1;
LCD_E = 1;
LCD_E = 0;
While (LCD_Data & 0x80); //Detect busy signal
Return(LCD_Data);
}
/************************Write data*********************** ************/
Void LCD_WriteData(uchar WDLCD)
{
LCD_ReadStatus();//Detect busy
LCD_Data = WDLCD
LCD_RS = 1;
LCD_RW = 0;
LCD_E = 1; / / If the crystal speed is too high, you can add a small delay after this
LCD_E = 1; / / delay
LCD_E = 0;
}
/************************Write command*********************** *********/
Void LCD_WriteCommand(uchar WCLCD,BuysC) //Buy busy detection when BuysC is 0
{
If (BuysC)
LCD_ReadStatus(); //Detect busy as needed
LCD_Data = WCLCD;
LCD_RS = 0;
LCD_RW = 0;
LCD_E = 1;
LCD_E = 1;
LCD_E = 0;
}
/*****************initialization******************************* ****/
Void LCD_Init(void)
{
LCD_Data = 0;
LCD_WriteCommand (0x38, 0); / / three display mode settings, do not detect busy signals
Delay_ms(5);
LCD_WriteCommand(0x38,0);
Delay5Ms();
LCD_WriteCommand(0x38,0);
Delay_ms(5);
LCD_WriteCommand(0x38,1); //Display mode setting, start to request busy signal every time
LCD_WriteCommand(0x08,1); //Close display
LCD_WriteCommand(0x01,1); //Show clear screen
LCD_WriteCommand(0x06,1); // Display cursor movement settings
LCD_WriteCommand(0x0C,1); // Display on and cursor settings
}
/***********************Display a character ************************* *********/
Void DisplayOneChar(uchar X, uchar Y, uchar DData)
{
Y &= 0x1;
X &= 0xF; //Restrict X cannot be greater than 15, Y cannot be greater than 1
If (Y) X |= 0x40; //When the second line is to be displayed, the address code is +0x40;
X |= 0x80; // Calculate the instruction code
LCD_WriteCommand(X, 0); //Do not detect busy signal here, send address code
LCD_WriteData(DData);
}
/************************Display a string of characters ********************* **********/
Void DisplayListChar(uchar X, uchar Y, uchar code *DData)
{
Uchar ListLength;
ListLength = 0;
Y &= 0x1;
X &= 0xF; //Restrict X cannot be greater than 15, Y cannot be greater than 1
While (DData[ListLength]》0x20) // quit if the end of the string is reached
{
If (X <<= 0xF) //X coordinate should be less than 0xF
{
DisplayOneChar(X, Y, DData[ListLength]); //Show a single character
ListLength++;
X++;
}
}
}
/************************************************* *****************/
Void main(void)
{
Delay_ms (400); / / start waiting, wait for the LCD to talk to the working state
LCD_Init(); //LCD initialization
Delay_ms(5); //Time delay (may not)
DisplayListChar(0, 1, up);
DisplayListChar(6, 0, down);
LCD_Data=0xff;
While(1);
}
Write lcd1602 display program with 16F877A#include《pic.h》
#define uchar unsigned char
#define uint unsigned int
#define DB PORTD //Define the port
#define rs RB0 #define e RB1
__CONFIG(0x3B31);
Const uchar data[]=“happy everydayâ€;//The first line of the input string
Const uchar data1[]="xiexie";//second line
Void init();
Void write_commond(uchar dat);//write instruction function
Void write_data(uchar dat);//write data function
Void delay(uint x);
Void delay(uint x)
{
Uint a,b;
For(a=x;a)0;a--)
For(b=110;b》0;b--); }
Void init () / / initialization instructions
{
Write_commond(0x01);//0000000001, clear the screen display
Write_commond(0x28);//Set 4-bit format, 2 lines, 5X7, function settings
Write_commond(0x0C);//0000001100, on display, no cursor, no flashing
Write_commond(0x06);//0000000110, set the input mode, the cursor moves to the right, the text on the screen does not move
Write_commond(0x14);//0001000100, set the CGRAM address display or cursor movement direction
}
Void write_commond(uchar dat)
{
Rs = 0; / / instruction DB = dat;
e=1; / / allow the falling edge trigger 1-0
Delay(5);
e=0;
DB=DB "4; / / left shift four bits from RD4 ~ RD7 into the LCD
Delay(5);
e=1; delay(5);
e=0;
}
Void write_data(uchar dat)
{
Rs=1;//data
DB=dat;
e=1;//allow
Delay(5);
e=0;
Delay(5);
DB=DB "4;
e=1;
Delay(5);
e=0;
}
Void main()
{
Uchar i;
TRISD=0X00; / / define the port register
PORTD=0X00;
PORTB=0X00;
TRISB=0X00;
Init();
Write_commond(0x80);//The address of the first row of DDRAM, without adding 0x10, can also start from // the leftmost
For(i=0;i"12;i++)
{
Write_data(data[i]);//The first line of data characters
Delay(5);
}
Write_commond(0xc0);//The second row of DDRAM address can also be added without 0x10
For(i=0;i"16;i++)
{
Write_data(data[i]);//The second line of data characters
Delay(5);
}
/* for(i=0;i"16;i++)
{
Write_commond(0x18);//The cursor does not move, the data shifts one bit to the left
Delay(5);
}*/
While(1);
}
Write a nearly character A program as follows:
#include《pic.h》
#define uchar unsigned char
#define uint unsigned int
#define DB PORTD
#define rs RB0
#define e RB1
__CONFIG(0x3B31);
Void init();
Void write_commond(uchar dat);//write instruction function
Void write_data(uchar dat);//write data function
Void disp_char(uchar x,uchar y,uchar dat);//Display a character at a certain position on the screen, x(0-16), y(1-2)
Void delay(uint x);
Void delay(uint x)
{
Uint a,b;
For(a=x;a)0;a--)
For(b=110;b》0;b--);
}
Void init () / / initialization instructions
{
Write_commond(0x01);//0000000001, clear the screen display
Write_commond(0x28);//Set 4-bit format, 2 lines, 5X7, function settings
Write_commond(0x0C);//0000001100, on display, no cursor, no flashing
Write_commond(0x06);//0000000110, set the input mode, the cursor moves to the right, the text on the screen does not move
Write_commond(0x80);//0001000100, set the CGRAM address display or cursor movement direction
}
Void write_commond(uchar dat)
{
Rs=0;//instruction
DB=dat;
e=1;//allow
Delay(5);
e=0;
DB=DB "4;
Delay(5);
e=1;
Delay(5);
e=0;
}
Void write_data(uchar dat)
{
Rs=1;//data
DB=dat;
e=1;//allow
Delay(5);
e=0;
Delay(5);
DB=DB "4;
e=1;delay(5);
e=0;
}
Void disp_char(uchar x,uchar y,uchar dat)
{
Uchar address;
If(y==1) address=0x80+x;
Else
Address=0xc0+x;
Write_commond(address);
Write_data(dat);
Delay(5);
}
Void main()
{
TRISD=0X00;
PORTD=0X00;
PORTB=0X00;
TRISB=0X00;
Init();
Disp_char(0,1,'A');
While(1);
}
It can also be as follows:
Void disp_char(uchar x,uchar y,uchar dat)
{
Uchar i;
Write_commond(0x80+x);
If(i=0;i"16;i++)
{
Write_data('A');
Delay(5);
}
}
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