17. [stm32] use only three wires to drive LCD1602 LCD

Author's brief introduction ： Hello, everyone , My name is DW, Share some of my new knowledge every day , Look forward to making progress with you
   
 
  Series column ：STM32
   
 

  Small experimental target ： Three wire drive LCD1602 liquid crystal
  If there is anything that is not well written, you are welcome to correct

  Development board ： The punctual atoms STM32F103Mini edition
Creation time ：2022 year 6 month 4 Japan

         Whether it is driven in serial mode LCD1602 LCD is also driven in parallel LCD1602 liquid crystal , Will occupy STM32 Too much IO mouth , So is there any way to reduce SCM IO What about the use of mouth ？ The answer is yes .

We can put two pieces 74HC595 The chip is driven in a cascaded manner LCD1602, This method only uses the 3 individual IO The mouth can drive LCD1602 了 .

        It has been introduced in detail in the article of four digit nixie tube 74HC595 How to use this chip , See the article for details ：15.[STM32] An article teaches you to use 75HC595 The chip drives the four digit nixie tube

         Add a function to write bytes on the basis of this article .

Write byte function

// Write byte function 
void LCD1602_Write_Byte(u8 dat,u8 dat1){
	
	for(u8 i=0;i<8;i++){
		
		((dat<<i)&0x80) ? DIO_High:DIO_Low;
		
		SCK_High;
		SCK_Low;
	}
	for(u8 i=0;i<8;i++){
		
		((dat1<<i)&0x80) ? DIO_High:DIO_Low;
		
		SCK_High;
		SCK_Low;
	}
	RCK_High;
	RCK_Low;
}

Tips ： Two pieces of 74HC595 Adopt cascade mode , So you need to send data twice .

  

       Next, write a function to write instructions and data , This function is the focus of this routine . What we need to write is 8 Bit data , But we only need to be in place ：RS、RW、EN（ Corresponding bit 0~2）, position 3~7 by 0.

         When we need to write data E、RW、RS by ：001, Therefore, the instructions to be written are 0000 0001（0x01） Next, you need to write the data to the bus , When E For high level, the data will be sent to the LCD , Therefore, the instructions to be written are ：0000 0101（0x05）, Need to be released later EN, So it needs to be rewritten 0x01;

         When we need to write instructions E、RW、RS by ：000, Therefore, the instructions to be written are 0000 0000（0x00）, Next, you need to write instructions to the bus , When E For high level, the data will be sent to the LCD , Therefore, the instructions to be written are ：0000 0100（0x04）, Need to be released later EN, So it needs to be rewritten 0x00;

Functions that write instructions and data

void LCD1602_Write_Cmd_Data(u8 cmd,u8 data){
	
	if(cmd){ //1  data  
		
		LCD1602_Write_Byte(data,0x01); //0000 0001 // E = 0 RW = 0 RS = 1
		delay_ms(3);
		LCD1602_Write_Byte(data,0x05); //0000 0101 // E = 1 RW = 0 RS = 1
		delay_ms(3);
		LCD1602_Write_Byte(data,0x01); //0000 0001 // E = 0 RW = 0 RS = 1
	}
	else{   //0  Instructions 
		
		LCD1602_Write_Byte(data,0x00); //0000 0000 // E = 0 RW = 0 RS = 0
		delay_ms(3);
		LCD1602_Write_Byte(data,0x04); //0000 0100 // E = 1 RW = 0 RS = 0
		delay_ms(3);
		LCD1602_Write_Byte(data,0x00); //0000 0000 // E = 0 RW = 0 RS = 0
	}
}

Tips ：

RS = 1: Writing data  RS = 0: Write instructions   

RW = 1: Read operations  RW = 1: Write operations  

EN: Read operation is highly effective  EN: Highly effective

Next, look at the hardware connection diagram .

         First piece 74HC595 Chip 11、12、14 The pins are respectively connected with the MCU PB0~PB2 Connected to a ,74HC595 Of 15、1、2 Pins and LCD1602 Of RS、R/W、E Pin to pin .

        Second piece 74HC595 Chip QA~QH Pin and LCD1602 Of D0~D7 Connected to a .

Tips ：

Of the first chip 9 Pin and the second chip 14 The pins are connected to each other

Two chip RCK、SCK Connect with each other

Let's take the last one DS18B20 The routines of the article are added , You can go to LCD1602 The temperature is displayed on the , Let's take a look at the experimental results . 

Today's sharing is here , Thank you for your patience in reading , If you find it useful, give me

This chapter ends , I'll see you in the next chapter

Reference material ：
1.STM32 Firmware library manual
2. The punctual atoms STM32 Incomplete manual _ Library function version
3. Reference video
4. Fundamentals of digital electronic technology  

Data uploaded , You need to take it yourself