LCD应用程序测试

Linux framebuffer绘图实践
本文详细介绍了在Linux环境下,如何利用framebuffer设备进行LCD屏幕绘图。从打开设备到获取屏幕信息,再到使用mmap映射内存并绘制点和线,全面展示了framebuffer的基本操作流程。特别注意了mmap参数设置及地址计算细节。
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
       
#include <sys/mman.h>

#include <linux/fb.h>

#define FB_DEV "/dev/fb0"       

#define SCREEN_RED   0xFF0000
#define SCREEN_GREEN 0x00FF00
#define SCREEN_BLUE  0x0000FF

void draw_point(unsigned int x,unsigned int y,unsigned int color);
void draw_line(unsigned int x0,unsigned int y0,unsigned int x1,unsigned int y1,unsigned int color);

static struct fb_var_screeninfo varScreenInfo = {0};
static struct fb_fix_screeninfo fixScreenInfo = {0};
static unsigned int *pfb_buffer = NULL;
int main(void)
{
    int ret = -1;
    int fd = -1;
    fd = open(FB_DEV, O_RDWR);
    if(fd < 0)
    {
        perror("open");
        close(fd);
        return -1;
    }
    ret = ioctl(fd, FBIOGET_FSCREENINFO,&fixScreenInfo);
    if(ret < 0)
    {
        perror("ioctl");
        close(fd);
        return ret;
    }
    
    ret = ioctl(fd, FBIOGET_VSCREENINFO,&varScreenInfo);
    if(ret < 0)
    {
        perror("ioctl");
        close(fd);
        return ret;
    }
    printf("smem_len = %d\n",fixScreenInfo.smem_len);
    printf("xres         = %d;  yres         = %d\n",varScreenInfo.xres,varScreenInfo.yres);
    printf("xres_virtual = %d;  yres_virtual = %d\n",varScreenInfo.xres_virtual,varScreenInfo.yres_virtual);
    
    pfb_buffer = mmap(NULL, fixScreenInfo.smem_len, PROT_READ|PROT_WRITE, MAP_SHARED,fd,0);
    printf("pfb_buffer = %p\n",pfb_buffer);
    draw_line(0,0,1023,599,SCREEN_RED);
    
    close(fd);    
    return 0;
}


void draw_point(unsigned int x,unsigned int y,unsigned int color)
{
    x %=varScreenInfo.xres_virtual;
    y %=varScreenInfo.yres_virtual;
    // printf("x = %d  y = %d   %p\n",x,y,(pfb_buffer + x + (y*varScreenInfo.xres_virtual)));
    *(pfb_buffer + x + y*varScreenInfo.xres_virtual) = color;
}
void draw_line(unsigned int x0,unsigned int y0,unsigned int x1,unsigned int y1,unsigned int color)
{
    unsigned int x=0,y=0;
    float setp = (y1-y0)/(float)(x1-x0);
    for(x=x0,y=y0;x<x1;x++)
    {
        draw_point(x,y,color);    
        y = y0+setp*(x-x0)        ;
    }
}
View Code

一. OS下操作LCD

    1.1. 在应用中通过framebuffer操作LCD

    1.2. framebuffer帧缓冲(简称fb)是linux内核中虚拟出的一个设备

    1.3. framebuffer向应用层提供一个统一标准接口的显示设备

    1.4. 从驱动来看,fb是一个典型的字符设备,而且创建了一个类/sys/class/graphics

二. 操作步骤

    2.1. 设备文件 /dev/fbx。 其中x代表0,1,2。。。

    2.2. 获取设备信息 #include <linux/fb.h>

    2.3. mmap做映射

    2.4. 填充framebuffer

三. 应用层开发注意事项

    3.1. 使用mmap函数时,参数int prot一定是PROT_READ|PROT_WRITE,我开发时笔误写成PROT_READ|PROT_READ,结果一直Segmentation fault。

    3.2. *(pfb_buffer + x + y*varScreenInfo.xres_virtual) = color;这里地址不用转换为char*进行运算

转载于:https://www.cnblogs.com/linux-37ge/p/10212540.html

#include //包含头文件 #include //包含固有函数 #define uint unsigned int //定义一下方便使用 #define uchar unsigned char //定义一下方便使用 #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_(); //一个时钟延时 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行为一页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--63,一般从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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