51 microcontroller | Example of realizing SMC1602 LCD screen display

LCD1602
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• 1602 means that each line displays 16 characters, and a total of two lines can be displayed. If it is a 12232 liquid crystal (graphic liquid crystal), it means that it is composed of 122 columns and 32 rows, that is, a total of 122*32 dots

• ps. Pay attention to the usage temperature. Usually the working range of liquid crystal is 0~+55℃, and the storage temperature range is -22~+60℃.

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Pin conditions:

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Basic operation sequence:

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RAM internal mapping: 80 bytes

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Status word description: //The status word reflects the current situation of the LCD screen. When STA7 is 1, it means that the display is busy. , cannot be operated

• STA0~STA6 represent the value of the current address pointer

• STA7 indicates read/write enable, =1 indicates base, =0 indicates permission
  

ps In principle, read and write detection must be performed before each read and write operation on the controller to ensure that STA7=0. In actual operation, since the operating speed of the microcontroller is slower than the response speed of the liquid crystal control, read and write detection may not be performed but only a brief Delay.

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Data pointer setting:
Users can access the internal 80-byte RAM through the following data address pointer to set the data address
80H+address code (0~27H, 40~67H)
Example: operate on the first address, 0x80+0x01
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-other Script code:

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Initialization:

• Display mode setting: 38H
  

• Display on/off and cursor settings
  

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Read and write operation timing:

• Read operation

• write operation
  

• Operating time parameters
  

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-Operation method:

• Operations on the LCD can be divided into two parts: data and instructions.

• By operating RS, R/W, and E, four operations are performed: read status, read data, write instructions, and write data.

• D0~D7 are used to input and output instruction codes and data

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LCD1602 usage examples:
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Design requirements:
Use LCD1602 to display two lines of characters, display two lines of words, and two buttons to control the display or clear the screen

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-Design ideas:

• Initialize LCD display //Refer to "Initialization" above
  

• Open enable

• Script operation
  

• Set 16*2 display, 5*7 dot matrix, 8-bit data structure

• Turn on the display, display the cursor without flashing

• After reading and writing characters, the address pointer +1, the cursor +1, and the entire screen display does not move.

• clear screen

• Set the first character of the address display

• initialization interrupt
  

• Turn on interrupts

• External interrupts 0 and 1

• Infinite loop waiting for interrupt

• key interrupt
  

• "Display" button
  

• Loop to write data (character array)

• Command "newline"

• Write the second row of data in a loop

• Button "clear screen"
  

• Command "clear screen"

• Subfunction //Refer to the "Read and Write Operation Timing Table" above
  

• write data

• write command

 1 #include

 2 typedef unsigned char uchar;

 3 sbit en = P3 ^ 4;

 4 sbit rs = P3 ^ 5;

 5 uchar code table1[] =

 6 {

 7 "SMC1602 0x01..."

 8 };

 9 uchar code table2[] =

10 {

11 "Hugh Dong."

12};

13 void Delay(uchar m)

14 {

15 uchar i, j;

16 for (i = m; i > 0; --i)

17 for (j = 110; j > 0; --j);

18}

19 /*Write data*/

20 void write_date(uchar date)

twenty one {

22 //Reference write operation timing diagram

23 rs = 1; //RS high level, write data

24 P2 = date; //Write data, corresponding to the timing diagram t_SP2 data establishment

25Delay(5);

26 en = 1; //Turn on the enable, give E a high pulse, and start writing data

27Delay(5);

28 en = 0; //Close enable and write data is completed

29 }

30 /* Write command*/

31 void write_com(uchar com)

32 {

33 //Basic principles are the same as writing data

34 rs = 0; //RS low level, write instruction

35 P2 = com;

36Delay(5);

37 en = 1;

38Delay(5);

39 en = 0;

40}

41 /* Initialize LCD */

42 voidInit()

43 {

44 en = 1;

45 write_com(0x38); //00111000 Set 16*2 display, 5*7 dot matrix, 8-bit data interface

46 write_com(0x0E); //00001110 Turn on display, display cursor, do not flash

47 write_com(0x06); //00000110 After reading and writing characters, the address pointer +1, the cursor +1, and the screen does not move