LCD驱动程序详细讲解(一)

本文详细介绍了TFT-LCD的工作原理,包括LCD接口、数据传输方式、S3C2440 LCD控制器的特性与结构。通过对显示器时序、像素数据组织的解析,展示了TFT-LCD如何通过控制寄存器设置实现图像显示,是嵌入式系统中LCD驱动程序的入门教程。

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平台:JZ2440V3

CPU:三星S3C2440A芯片

LCD:4.3寸液晶屏手册_AT043TN24

LCD介绍:

LCD,即液晶显示器,是一种采用了液晶控制透光技术来实现色彩的显示器。LCD有很多种类型,比如STN、TFT、LTPS、OLED等。各有优缺点。

由于JZ2440V3开发板上面配置的是TFT类型液晶显示器,所以本文主要针对TFT-LCD进行讲解;

TFT(Thin Film Transistor,薄膜晶体管)可以大大缩短屏幕的响应时间,其响应时间已经小于80ms,并改善了连续显示时屏幕模糊闪烁,有效提高了动态画面的播放力,呈现画面色彩饱和度、真实效果和对比度都非常不错,只是功耗稍高,是目前最为主流的液晶显示器。

LCD的接口:

CPU或显卡发出的图像数据是TTL信号,LCD本身接收的也是TTL信号。由于TTL信号在高速率的长距离传输时性能不佳,抗干扰能力也比较差,后来又提出了多种接口来解决这种问题,比如LVDS、TDMS、GVIF、DVI和DFP等。它们实际上只是将CPU或显卡发出的TTL信号编码成各种信号以便传输,在LCD那边将接收到的信号进行解码得到TTL信号。

由于数字接口标准尚未统一,所以使用LCD时需要根据其手册了解具体接口定义。也是基于数字接口标准尚未统一的原因,市场上大多LCD都采用模拟信号接口,LCD需要先通过ADC将模拟信号转换为数字信号才能显示。

但是,不管采用何种数字接口,本质的TTL信号是一样的。

TFT-LCD的数据传输方式有2种,单扫:指的是对于一整屏的数据,从上到下,从左到右,一个一个地发送出来,双扫:是指将一整屏的数据分为上下两部分,同时的从上到下,从左到右,一个一个的发送出来。

其中,TFT-LCD其数据信号多达24根,对应像素值中的每一位。

TFT-LCD的TTL信号:

信号名称      描述           
VSYNC 垂直同步信号
HSYNC 水平同步信号
VD[23:0] 数据信号
HCLK 时钟信号
LEND 行结束信号
PWREN 电源开关信号

S3C2440 LCD控制器的特性和结构:

S3C2440 LCD控制器被用来向LCD传输图像数据,并提供必要的控制信号,比如VFRAME、VLINE、VCLK、VM等。可以支持STN-LCD和TFT-LCD,其特性如下(BPP表示bit per pixel,即每个像素用多少位来表示其颜色)。

S3C2440 LCD控制器的内部结构如下图1所示:

154923_6Mfy_2888084.png

                                                      图 1

其中,REGBANK是LCD控制器的寄存器组,包含17个寄存器和一块256*16的调色板内存,用来设置各项参数。而LCDCDMA则是LCD控制器专用的DMA信道,可以自动的从系统总线上取到图像数据,这使得显示图像时不需要CPU的干涉。VIDPRCS将LCDCDMA中的数据组合成特定的格式(比如4位单扫,4位双扫和8位单扫等),然后从VD[23:0]发送给LCD屏。同时,TIMEGEN和LPC3600负责产生LCD屏所需的控制时序,例如VSYNC、HSYNC、VCLK、VDEN,然后从VIDEO MUX送给LCD屏。

显示器上数据的组织格式:

对于屏幕上的一整幅图像,他的数据是如何组织的?无论是CRT显示器还是LCD显示器,他们都有相同的概念。

一幅图像被称为一帧(frame),每帧由多行组成,每行由多个像素组成,每个像素的颜色使用若干位的数据来表示。对于单色显示器,每个像素使用1位来表示,称为1BPP;对于256色显示器,每个像素使用8位来表示,被称为8BPP。

显示器从屏幕的左上方开始,一行一行的取得每个像素的数据并显示出来,当显示到一行的最右边时,跳到下一行的最左边开始显示下一行;当显示完所有行后,跳到左上方开始下一帧。显示器沿着“Z”字型的路线进行扫描,使用HSYNC、VSYNC信号来控制扫描路线的跳转,HSYNC表示“是跳到最左边的时候了”,VSYNC表示“是跳到最上边的时候了”。

在工作中的显示器上,可以在四周

#include //包含头文件 #include //包含固有函数 #define uint unsigned int //定义下方便使用 #define uchar unsigned char //定义下方便使用 #define DATA P0 //LCD12864数据线 sbit RS=P2^2; // 数据\指令 D、I 选择 sbit RW=P2^1; // 读\写 选择 R、W sbit EN=P2^0; // 读\写使能 sbit cs1=P2^4; // 片选1 sbit cs2=P2^3; // 片选2 /********************************/ /* 定义图形字库 */ uchar code Hzk[]={ //左屏幕第1页 0xFF,0xFF,0xFF,0xFF,0x7F,0xBF,0x3F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, //左屏幕第2页 0xFF,0xFF,0xFF,0xAB,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, //左屏幕第3页 0xFF,0xFF,0xFF,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0xE0,0xEA,0xE0,0xEA, 0xE0,0xEA,0xE0,0xEA,0xE0,0xEA,0xC0,0xAA,0x00,0xAA,0xE0,0xEA,0xE0,0xEA,0xE0,0xEA, 0xE0,0xEA,0xE0,0xEA,0xE0,0xEA,0x80,0xAA,0x00,0xAA,0x00,0xAA,0xC0,0xEA,0xE0,0xEA, 0xE0,0xEA,0xE0,0xEA,0xC0,0xEA,0x80,0xAA,0x00,0xAA,0xE0,0xEA,0xE0,0xEA,0xE0,0xEA, //左屏幕第4页 0xFF,0xFF,0xFF,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0xFF,0xFF,0xFF,0xFF, 0x38,0xBA,0x38,0xBF,0x3F,0xBF,0x1F,0xAF,0x00,0xAA,0xFF,0xFF,0xFF,0xFF,0xFF,0xBA, 0x78,0xFA,0xFD,0xFF,0xDF,0xBF,0x0F,0xAA,0x00,0xFE,0xFF,0xFF,0xFF,0xFF,0x01,0xAA, 0x00,0xAA,0x01,0xEF,0xFF,0xFF,0xFF,0xFE,0x00,0xAA,0x00,0xAA,0x00,0xAA,0xFF,0xFF, //左屏幕第5页 0xFF,0xFF,0xFF,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x0F,0xAF,0x0F,0xAF, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x0F,0xAF,0x0F,0xAF,0x0F,0xAA, 0x00,0xAA,0x03,0xAF,0x0F,0xAF,0x0F,0xAE,0x00,0xAA,0x01,0xAB,0x07,0xAF,0x0F,0xAE, 0x0E,0xAE,0x0F,0xAF,0x07,0xAF,0x03,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x0F,0xAF, //左屏幕第6页 0xFF,0xFF,0xFF,0xEA,0x80,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, //左屏幕第7页 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, //左屏幕第8页 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, //右屏幕第1页 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF, 0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x1F,0xBF,0x3F,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第2页 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x01,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第3页 0xE0,0xEA,0xE0,0xEA,0xE0,0xEA,0xE0,0xAA,0x00,0xEA,0xE0,0xEA,0xE0,0xEA,0xE0,0xEA, 0xE0,0xEA,0xE0,0xEA,0xE0,0xAA,0x00,0xAA,0xE0,0xEA,0xE0,0xEA,0x00,0xAA,0x00,0xAA, 0x00,0xEA,0xE0,0xEA,0xE0,0xAA,0x00,0xAA,0x80,0xEA,0xC0,0xEA,0xE0,0xEA,0xE0,0xEA, 0xE0,0xEA,0x80,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第4页 0xFF,0xFF,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xFF,0xFF,0xFF,0xFF,0xBA,0x38,0xBA, 0x38,0xBA,0x38,0xBA,0x00,0xAA,0x00,0xAA,0xFF,0xFF,0xFF,0xFF,0x00,0xAA,0x00,0xAA, 0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0x00,0xAA,0x8F,0xAF,0x9F,0xBF,0x3C,0xBE,0x38,0xFB, 0xFB,0xFB,0xF3,0xEB,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第5页 0x0F,0xAF,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAF,0x0F,0xAF,0x0F,0xAE,0x0E,0xAE, 0x0E,0xAE,0x0E,0xAE,0x0E,0xAA,0x00,0xAA,0x03,0xAF,0x07,0xAF,0x0F,0xAE,0x0E,0xAE, 0x0F,0xAF,0x07,0xAB,0x01,0xAA,0x00,0xAB,0x03,0xAF,0x07,0xAF,0x0E,0xAE,0x0E,0xAF, 0x0F,0xAF,0x07,0xAB,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第6页 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA, 0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0x00,0xAA,0xE0,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第7页 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE, 0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFE,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00, //右屏幕第8页 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x00, }; /*状态检查,LCD是否忙*/ void CheckState() { uchar dat;//状态信息(判断是否忙) RS=0; // 数据\指令选择,D/I(RS)=“L” ,表示 DB7∽DB0 为显示指令数据 RW=1; //R/W=“H” ,E=“H”数据被读到DB7∽DB0 do{ DATA=0x00; EN=1; //EN下降源 _nop_(); //个时钟延时 dat=DATA; EN=0; dat=dat>>7; //仅当第7位为0时才可操作(判别busy信号) }while(!(dat==0x00)); } /*写命令到LCD中*/ SendCommandToLCD(uchar com) { CheckState();//状态检查,LCD是否忙 RS=0; //向LCD发送命令。RS=0写指令,RS=1写数据 RW=0;//R/W=“L” ,E=“H→L”数据被写到 IR 或 DR DATA=com; //com :命令 EN=1;//EN下降源 _nop_(); _nop_(); EN=0; } /*设置页 0xb8是页的首地址*/ void SetLine(uchar page) { page=0xb8|page; //1011 1xxx 0<=page<=7 设定页地址--X 0-7,8行为页64/8=8,共8页 SendCommandToLCD(page); } /*设定显示开始行,0xc0是行的首地址*/ void SetStartLine(uchar startline) { startline=0xc0|startline; //1100 0000 SendCommandToLCD(startline); //设置从哪行开始:0--63,般从0 行开始显示 } /*设定列地址--Y 0-63 ,0x40是列的首地址*/ void SetColumn(uchar column) { column=column &0x3f; //column最大值为64,越出 0=<column<=63 column= 0x40|column; //01xx xxxx SendCommandToLCD(column); } /*开关显示,0x3f是开显示,0x3e是关显示*/ void SetOnOff(uchar onoff) { onoff=0x3e|onoff; //0011 111x,onoff只能为0或者1 SendCommandToLCD(onoff); } /*写显示数据 */ void WriteByte(uchar dat) { CheckState();//状态检查,LCD是否忙 RS=1; //RS=0写指令,RS=1写数据 RW=0;////R/W=“L” ,E=“H→L”数据被写到 IR 或 DR DATA=dat;//dat:显示数据 EN=1; //EN下降源 _nop_(); _nop_(); EN=0; } /*选择屏幕screen: 0-全屏,1-左屏,2-右屏*/ void SelectScreen(uchar screen) { switch(screen) { case 0: cs1=0;//全屏 _nop_(); _nop_(); _nop_(); cs2=0; _nop_(); _nop_(); _nop_(); break; case 1: cs1=0;//左屏 _nop_(); _nop_(); _nop_(); cs2=1; _nop_(); _nop_(); _nop_(); break; case 2: cs1=1;//右屏 _nop_(); _nop_(); _nop_(); cs2=0; _nop_(); _nop_(); _nop_(); break; } } /*清屏screen: 0-全屏,1-左屏,2-右*/ void ClearScreen(uchar screen) { uchar i,j; SelectScreen(screen); for(i=0;i<8;i++) //控制页数0-7,共8页 { SetLine(i); SetColumn(0); for(j=0;j<64;j++) //控制列数0-63,共64列 { WriteByte(0x00); //写点内容,列地址自动加1 } } } /*延时程序*/ void delay(uint z) { uint i,j; for(i=0; i<z; i++) for(j = 0; j < 110; j++); } /*向上滚屏*//*这里用做滚动显示*/ void lcd_rol() { uint i; for(i = 0; i < 64; i++) { cs1=0; // 片选1 SendCommandToLCD(0xc0+i); cs1=1; cs2=0;// 片选2 //SendCommandToLCD(0xc0+62-i); SendCommandToLCD(0xc0+i); cs2=1; // 片选2 delay(100);
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