Lecture 8: 1602 LCD (Guo Tianxiang)

explain ： This article is just some records of my learning process , If there is any infringement , Please contact me to delete , There are inevitably omissions and mistakes in the article , Welcome to point out .

One 、1602 Liquid crystal introduction

LCD belongs to extended content , however , It's used a lot of times , After all, you need a visual result to provide to users , So we need to master the use of LCD .

1602 Model LCD , among 16 Express 1 Rows can show 16 Characters ,02 Expressing common ownership 2 That's ok .

Allied , also 1601、0801、0802...

Some models are 12864、12232 This kind of graphic liquid crystal , for example 12864 It's horizontal 128 A little bit , Vertical yes 64 A little bit , These points form a graph . And the character LCD mentioned above , Only characters can be displayed . These can be learned in the description document .

notes ： The teacher said , Now that you have learned liquid crystal , Then try not to use digital tubes if you can use LCD , Because by comparison , LCD is simpler , And more interesting .

Two 、 Learn how to operate through documents 1602 liquid crystal

1. There is a Chinese document in the material sent by the teacher , First look at the LCD pin function ：

Look at the connection diagram of the development board ：

You can see the 5 The pin is directly connected to the ground , Because here we only need to write data into the LCD , There is no need to read data . So just manipulate the 4 And the 6 Pin can be .

2. Next, let's look at the detailed interface description ：

The reason to make sure STA7 = 0, Because STA7 It is the read-write operation enable , Only in the allowed position , To read and write . Because the frequency of crystal oscillator is not very high in MCU , Therefore, there is no need to think too much . It mainly takes time for LCD to write data , But in the use of DSP、 When embedded chips are running at high speed , Sometimes the LCD didn't display completely last time , The next display request is coming , And if the read / write operation is enabled , It may cause the loss of display data . Therefore, we should carry out corresponding processing through read-write detection .

notes ：

High pulse ： From low to high to low is a high pulse .

Low pulse ： In turn, , High and low is a low pulse .

3. Next, let's look at the sequence of write operations in detail ：

We know from the previous documentation ,RS The difference of represents the difference between writing instructions and writing data .

and R/W We have defaulted to grounding . So by right RS、E The operation of can realize the writing of instructions or data .

So we write two functions , Used to write instructions and write data respectively ：

The write instruction function is as follows ： 

void write_com(uchar com)// Write instructions / command 
{
	lcdrs = 0;
	//RW = 0;// The development board has been grounded by default 
	P0 = com;//com For instructions 
	delay(5);
	lcden = 1;
	delay(5);
	lcden = 0;
}

The function of writing data is as follows ：

void write_data(uchar date)// Writing data 
{
	lcdrs = 1;
	//RW = 0;// The development board has been grounded by default 
	P0 = date;//date For data 
	delay(5);
	lcden = 1;
	delay(5);
	lcden = 0;
}

Because the requirement of real-time is not high , So the timing parameters are only simple delay Function substitution , The actual development process may need attention .

There is also the read-write detection mentioned above , In a simple single-chip program, it can also be omitted , We just need simple delay Function delay , The delay time is greater than the speed of LCD writing .

4.RAM Address map

Each box represents an address , Write data content to the address , Then the content will be displayed in this place . And the first line in the back 10 To 27 And the second line 50 To 67 Not part of the display , But we can choose to write the content behind this first , Then move the whole screen , Move the content behind this to the screen .

5. Instructions ：

Send instructions before you start , To set the display mode . There is only one mode in Chinese documents , There should be other instructions in the detailed English document , In actual development, we should try to write the program according to the original file .

            

Then there is the display switch and cursor setting .

Notice the top N=1 When reading or writing a character, add one to the address pointer , Because of the data pointer that will be mentioned later , We need to set the data pointer , Then the content will be displayed at the position pointed by the data pointer , When we want to write a row of data , We need to set multiple data pointers , And if the address pointer will automatically add 1, We don't need to set , Just write the data .

Setting of data pointer , Preparation before writing data .

Other settings , There are many, many settings , You can find... In the documentation .

3、 ... and 、 Use 1602 liquid crystal , First line display “I AM hong!”, The second line shows “I LIKE MCU!”

#include <reg52.h>
#define uint unsigned int
#define uchar unsigned char
sbit lcden = P3^4;
sbit lcdrs = P3^5;
sbit dula = P2^6;
sbit wela = P2^7;
void delay(uint z);
uchar num;
uchar code table[]="I AM hong!";
uchar code table1[]="I LIKE MCU!";
void write_com(uchar com)// Write instructions / command 
{
	lcdrs = 0;
	//RW = 0;// The development board has been grounded by default 
	P0 = com;
	delay(5);
	lcden = 1;
	delay(5);
	lcden = 0;
}
void write_data(uchar date)// Writing data 
{
	lcdrs = 1;
	//RW = 0;// The development board has been grounded by default 
	P0 = date;
	delay(5);
	lcden = 1;
	delay(5);
	lcden = 0;
}
void init()
{
	dula = 0;
	wela = 0;// Turn off the nixie tube 
	lcden = 0;
	write_com(0x38);// Display mode settings 
	write_com(0x0c);// Show on / Turn off cursor setting 
	write_com(0x06);// Address pointer plus 1,N=1,S=0
	write_com(0x01);// The display is clear , Because there is a data in it by default , There is a black block on the screen 
	write_com(0x80);// Data pointer setting 
}
void main()
{
	init();
	for(num = 0;num < 10;num++)
	{
		write_data(table[num]);
		delay(200);
	}
	write_com(0x80+0x40);// The second line 
	for(num = 0;num < 11;num++)
	{
		write_data(table1[num]);
		delay(200);
	}
	while(1);
}

void delay(uint z)  // The time delay function ,z The value of is the delay of this function ms Count , Such as delay(200); About time delay 200ms.
{					//delay(500); About time delay 500ms.
	uint x,y;
	for(x=z;x>0;x--)
		for(y=110;y>0;y--);	
}