（18） LCD1602 experiment

        In this section, we will complete the programming of another display on the MCU , Use LCD1602 LCD to display the characters we want to output , Output "I LOVE MCU" and “MCU LOVE I” These two short strings . Finish us 51 The last simple experiment of single chip microcomputer , After that, you may directly put several simple projects on it , Deepen for 51 Understanding of SCM .

  About LCD1602

        1602 Liquid crystal is also called LCD1602 Character LCD , It can show 2 Line character information , Each line can show 16 Characters , It is a kind of special used to display letters 、 Numbers 、 Dot matrix liquid crystal module of symbol , Each of us LCD1602 Modules may be different , But their usage is basically the same , stay LCD1602 Contains 80 Bytes of DDRAM, They are used to display characters . The corresponding relationship between the address and the screen is as follows ：

         Only one 0x00 To 0x0f and 0x40 To 0x4f It is used to display , The rest can only be used for storage , And about the LCD1602 When we write addresses, each address is added correspondingly 0x80 To reach the corresponding address , For example, you should be in 0x00 This address writes a value , So we need to be in 0x80 Write value , It means that every address has one 0x80 The migration , And about the LCD1602 We have some commonly used instructions to control it ,

among （1） Clear screen instruction :0x01, (2) Mode setting instruction , The instruction format is as follows ：

among DB1 The meaning is ：

0: After writing data, the cursor moves left                 1: After writing data, the cursor moves to the right

among DB0 The meaning is ：

0： The display does not move after writing data        1: After writing the data, the whole display screen moves to the right by one unit

(3) Display switch control command , The instruction format is as follows :

among DB2 The meaning is ：

0： Display function off                                    1： Display function on

among DB1 The meaning is ：

0： No cursor                                             1： There are cursors

among DB0 The meaning is :

0： The cursor blinks                                           1： The cursor does not flash

(4) display mode , Our default setting 16*2 Show ,5*7 Lattice ,8 Bit interface , Then our default instruction is 0x38

About hardware

         Among them, there are three control interfaces connected with the single chip microcomputer RS,WR,EN, rest D0 To D7 It's a data port , Used to transmit data , The basic timing is as follows

Read status ： Input ：RS=L,R/W=H, EN = H        Output :D0~D7 Status word

We can't read the corresponding data

Write instructions ： Input ：RS=L, R/W=L, D0~D7= Instruction code ,E= High pulse Output :D0~D7= data

Writing data ： Input ：RS=H,R/W=L,D0~D7= data ,E= High pulse         Output ： nothing

As for each reading and writing, we may delay , In fact, we don't need to be so accurate , Because most liquid crystal displays are nanosecond , And our MCU is not so fast , But in order to stabilize the delay , We will still do a short delay .

About software ：

ds1602 The main functions of are as follows ：

#include "reg52.h"
sbit lcd_en = P2^7; 
sbit lcd_rs = P2^6;
sbit lcd_rw = P2^5;
void delay_us(unsigned int xus){
	while(xus--);
}

void lcd1602_write(unsigned char dat, int flag){
	  lcd_en = 0;
	  lcd_rs = flag;
	  lcd_rw = 0;
	  
	  P0 = dat;
	  delay_us(500);
	  lcd_en = 1;
	  delay_us(100);
	  lcd_en = 0;
}

void lcd1602_init(){
	lcd1602_write(0x38, 0);
	lcd1602_write(0x0c, 0);
	lcd1602_write(0x06, 0);
	lcd1602_write(0x01, 0);
	lcd1602_write(0x80, 0);
}

Its header file is as follows ：

#ifndef _LCD1602_H_
#define _LCD1602_H_
#include "reg52.h"
void delay_us(unsigned int xus);
void lcd1602_write(unsigned char dat, int flag);
void lcd1602_init();
#endif

Its main function is as follows ：

#include <reg52.h>
#include "ds1602.h"

unsigned char table0[] = {"I LOVE MCU"};
unsigned char table1[] = {"MCU LOVE I"};
void main(){
	int i;
	lcd1602_init();
	lcd1602_write(0x80 + 0x03 , 0);
	for(i = 0; i < 10;i++){
		lcd1602_write(table0[i], 1);
		delay_us(100);
	}
	 lcd1602_write(0x80 + 0x40 + 0x03, 0);
	for(i = 0;i < 10;i++){
		lcd1602_write(table1[i], 1);
		delay_us(100);
	}
	while(1){				
	}
}