Application examples and source code of ordinary 51 microcontroller driving 3.5-inch TFT!

　　The 3.5-inch screens popular in the market are basically built-in drivers without controllers, which makes it difficult for users to use them. Basically, many friends choose ARM7 or ARM9 with LCD controllers to develop color screens. For friends who don’t know how to develop ARM, they only use ordinary MCUs, so it is difficult to find 3.5-inch TFT modules that can be selected.

　　This article is written based on a 3.5-inch TFT module that is commonly used on the market. Users only need to use the TFT module as a common monochrome LCD development idea, and they can program it easily.

　　1. Hardware Selection

　　1. MCU: AT89S51

　　2. Development and compilation environment: Keil C51

　　3. 3.5-inch TFT module model: MzT35C1

　　2. Basic performance of TFT module:

　　1. Basic parameters

　　Module structure: built-in controller

　　Screen size: 3.5 inches

　　Screen resolution: 320*240

　　Screen colors: 65536 colors (16-bit true color)

　　Working voltage : 3.3V/5V optional

　　Bus architecture: Intel8080

　　Bus width: 8Bit

　　Backlight type:   LED ; command control, 0-127 adjustable

　　Connection method: Pin header socket

　　Touch screen: standard configuration without touch screen; the module has touch screen chip pads and touch screen interface

　　2. Interface pin description

　　3. Operation timing (8-bit parallel Intel 8080 bus)

　　The MzT35C1 module supports the Intel 8080 bus, and the maximum bus speed can reach 20 MHz (of course, whether the bus speed can reach the maximum interface speed is also related to the user's bus wiring, line length, etc.). In other words, if the control MCU speed is fast enough, it can support video display.

Note: The bus interface of the MzT35C1 module is 8-bit, which means that when operating the data of the video memory, two operations are required to complete it, first transmit the high byte and then the low byte; but for the operation of the register (writing the register address, that is, the write operation when A0 is low), only 8-bit operations are required.

　　3. MzT35C1 and 51 hardware interface connection diagram

　　This example uses GPIO to simulate bus timing. The module in the figure above is powered by 5V, and the port level of the module is 3.3V, so a 100-ohm resistor is connected in series between all 51 ports and the module . Other circuits related to MCS51 are not drawn in the figure. Please refer to other development board documents for details. The relevant pins of the MzT35C1 module in the figure shall be subject to the actual object. The figure only shows the ports with corresponding names. Please pay attention when using it for reference.

　　3. Low-level driver code writing method

　　1. Port configuration

　　#include "REG52.h"

　　#include "intrins.h" //Include this header file to directly operate the kernel registers and some defined macros

　　#define LCD_ CTR l_GPIO() //Undefined

　　#define LCD_Ctrl_Out() LCD_CS_SET();LCD_RD_SET();LCD_RW_SET();

　　#define LCD_Ctrl_Set(n) //Undefined

　　#define LCD_Ctrl_Clr(n) //Undefined

　　sbit LCD_CS = P2^6;

　　#define LCD_CS_SET() LCD_CS = 1

　　#define LCD_CS_CLR() LCD_CS = 0

　　sbit LCD_RE = P3^5;

　　#define LCD_RE_SET() LCD_RE = 1

　　#define LCD_RE_CLR() LCD_RE = 0

　　sbit LCD_A0 = P2^5;

　　#define LCD_A0_SET() LCD_A0 = 1

　　#define LCD_A0_CLR() LCD_A0 = 0

　　sbit LCD_RW = P3^6;

　　#define LCD_RW_SET() LCD_RW = 1

　　#define LCD_RW_CLR() LCD_RW = 0

　　sbit LCD_RD = P3^7;

　　#define LCD_RD_SET() LCD_RD = 1

　　#define LCD_RD_CLR() LCD_RD = 0

　　#define LCD_Data_GPIO() //51's port is bidirectional, so there is no need to specify the direction, so there is no definition

　　#define LCD_Data_Out() //51's port is bidirectional, so there is no need to specify the direction, so there is no definition

　　#define LCD_Data_In() P0 = 0xff //Port 51 needs to output 0xff before reading data

　　#define LCD_Data_BUS_Clr() //Undefined

　　#define LCD_Data_BUS_Set(n) P0 = n

　　#define LCD_Data_Read() P0

　　2. Write data and instruction operations

　　//==============================================

　　// Function: void LCD_DataWrite(unsigned int Data)

　　// Description: Write a word (16 bits) of display data to the display buffer RAM in the LCD

　　// Parameter: Data The data to be written

　　//==============================================

　　#defineLCD_DataWrite(n) LCD_A0_SET();LCD_CS_CLR();LCD_Data_BUS_Clr();LCD_Data_BUS_Set((unsigned char)(n>>8));\

　　LCD_RW_CLR();LCD_RW_SET();LCD_Data_BUS_Clr();LCD_Data_BUS_Set((unsigned char)n);LCD_RW_CLR();\ LCD_RW_SET();LCD_CS_SET()

　　//================================================ =====

　　// Function: void LCD_RegWrite(unsigned char Addr, unsigned int Command)

　　// Description: Write one byte of data to the control register in the LCD

　　// Parameter: Addr The address of the register to be written, the lower eight bits are valid (byte)

　　// Command write data

　　//================================================ =====

　　#define LCD_RegWrite(n)

　　LCD_A0_CLR();LCD_CS_CLR();LCD_Data_BUS_Clr();LCD_Data_BUS_Set(n);\

　　LCD_RW_CLR();LCD_RW_SET();LCD_CS_SET()

　　2. Read data operation

　　//==============================================

　　// Function: LCDBYTE LCD_DataRead(void)

　　// Description: Read one byte of display data from the display buffer RAM in the LCD

　　// Parameters: None

　　// Return: the read data,

　　// Note: Mz general version LCD driver standard sub function

　　//============================================

　　LCDBYTE LCD_DataRead(void)

　　{

　　LCDBYTE Read_Data;

　　LCD_Data_In();

　　LCD_A0_SET();

　　LCD_CS_CLR();

　　LCD_RD_CLR();

　　LCD_RD_SET();

　　LCD_RD_CLR();

　　LCD_RD_SET(); //The previous operation requires a complete empty read operation before data can be read

　　//If the user needs to read the video memory continuously, only one operation is required for the first read.

　　// Second empty read operation

　　LCD_RD_CLR();

　　Read_Data = LCD_Data_Read();

　　Read_Data = Read_Data<<8;

　　LCD_RD_SET();

　　LCD_RD_CLR();

　　Read_Data |= LCD_Data_Read();

　　LCD_RD_SET();

　　LCD_CS_SET();

　　LCD_Data_Out();

　　return Read_Data;

　　}

　　3. Initialize TFT operation

　　void LCD_Init(void)

　　{

　　// FLASH *Init_String;

　　//Initialization of the port used by the LCD driver

　　LCD_PortInit();

　　//According to the LCD display configuration, set the LCD data address pointer to automatically increase the feature

　　//end

　　LCD_RE_CLR();

　　TimeDelay(5);

　　LCD_RE_SET();

　　LCD_RegWrite(0x03);

　　LCD_DataWrite((1<<7)| (0x60<<0)); //Set backlight control to enable and backlight brightness level to 60 (0~127)

　　LCD_RegWrite(0x04); //Write system register

　　// LCD_DataWrite((0<<7)| //Current display page

　　// (0<<6) | //Current read-write page settings

　　// (1<<0)); //Display switch

　　LCD_DataWrite(MzT35_Ctrl_Reg);

　　/* Init_String = Initial_Tab;

　　while(Init_String!=0xffff)

　　{

　　LCD_RegWrite(0x05);LCD_DataWrite(*Init_String++);

　　LCD_RegWrite(0x06);LCD_DataWrite(*Init_String++);

　　}*/

　　LCD_Fill(LCD_INITIAL_COLOR);

　　}