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嵌入式Linux下完成LCD屏文字显示(帧缓冲框架)

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嵌入式Linux下完成LCD屏文字显示(帧缓冲框架)这篇文章就介绍在应用层 如何利用帧缓冲框架接口封装LCD屏的画点函数，获取LCD屏的硬件信息，完成对LCD屏编程，实现文字、数字显示。

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1.前言

帧缓冲框架是Linux下专门为显示类设备设计的接口，目的是将硬件和软件层分离开，方便应用层的编程，也方便应用层程序移植。帧缓冲框架向驱动层和应用层分别提供了一套标准接口，驱动层按照框架编写驱动，应用层按照框架编写应用程序。帧缓冲在/dev目录下生成的标准节点是fb，比如：/dev/fb0,/dev/fb1等等。

这篇文章就介绍在应用层 如何利用帧缓冲框架接口封装LCD屏的画点函数，获取LCD屏的硬件信息，完成对LCD屏编程，实现文字、数字显示。当期的文字采用点阵方式取模来完成显示，比较简单，与单片机上的LCD编程思路一样，可以更方便快速学习帧缓冲编程。后续正常开发中一般采用矢量字库完成字体显示，大小调整方便，字体更换方法，在前面文章有介绍过嵌入式Linux如何交叉编译freetype库。

image.png

2. 编程思路

下面是帧缓冲框架图： image.png

image.png

帧缓冲设备是标准的字符设备，通过open函数打开设备，再通过ioctl接口获取LCD屏的一些硬件参数信息，在利用mmap函数映射LCD屏的地址到应用层。映射的这个地址就相当于是LCD屏的显存地址，对这个地址里写入数据就可以在LCD屏硬件上实时显示出来。

int fd=open("/dev/fb0",O_RDWR);
    if(fd<0)
    {
        perror("设备文件打开失败");
        return 0;
    }
    
    /*1. 获取LCD屏的可变形参*/
    ioctl(fd,FBIOGET_VSCREENINFO,&var);
    printf("分辨率:%d*%d\n",var.xres,var.yres);
    printf("像素点位数:%d\n",var.bits_per_pixel);
    
    /*2. 获取LCD屏的固定形参*/
    ioctl(fd,FBIOGET_FSCREENINFO,&fix);
    printf("映射的长度:%d\n",fix.smem_len);
    printf("一行的字节数:%d\n",fix.line_length);
    
    /*3. 映射LCD缓冲区地址到进程空间*/
    fb_mem=mmap(NULL,fix.smem_len,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
    if(fb_mem==NULL)
    {
        perror("空间映射失败!\n");
        return 0;
    }

在应用mmap函数将驱动的DMA缓冲区地址映射到进程空间之后，如何控制LCD呢？ 为了方便对LCD屏进行操作，需要封装一个画点函数。然后后续的图片显示，文字显示，其他图形显示都基于这个画点函数来完成，程序就很好设计。

当前采用的LCD屏是800*480分辨率，24位像素，通过这些参数就可以编写一个公式，封装画点函数。 image.png

下面是封装好的函数原型：fb_mem是LCD屏映射的地址，后面的参数是获取的LCD屏硬件参数信息。

/* 函数功能: 画点 */
void Show_Pixel(int x,int y,int color) {
    unsigned int *lcd=(unsigned int *)(fb_mem+y*var.xres*var.bits_per_pixel/8+x*var.bits_per_pixel/8);
    *lcd=color; //颜色赋值
}

有了画点函数，就可以封装中文显示函数： 下面这个函数是针对横向取模的点阵字模进行描点的，其他取模方式根据情况修改即可。

/* 函数功能: 显示中文 说明: 取模的字体是按照横向取模进行取点阵码。       取模的字体宽度是8的倍数。 */
void ShowFont(int x,int y,int size,unsigned char *data) {
    int i,j,x0=x;
    unsigned char tmp;
    for(i=0;i<size/8*size;i++)
    {
        tmp=data[i];
        for(j=0;j<8;j++)
        {
            if(tmp&0x80)Show_Pixel(x0,y,0xFF0033);
            //else 画背景色
            x0++;
            tmp<<=1;
        }
        if(x0-x==size)
        {
            y++;
            x0=x;
        }
    }
}

中文可以显示，照着思路再封装一个字母数字的显示接口：

/* 函数功能: 显示一个ASCII码。“空格开始 到 ~ 结束” !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~ ​ 说明: ASCII码取模 宽度和高度必须是8的倍数，传入的size(高) */
void ShowASCII(int x,int y,int size,unsigned char c_data) {
    int i,j,x0=x;
    unsigned char data;
    int cnt;
    if(c_data<' ' ||  c_data > '~')return; 
    cnt=c_data-' ';
    for(i=0;i<size/2/8*size;i++)
    {
         switch(size)
         {
            case 16:
                break;
             case 32:
                data=ASCII_16_32[cnt][i];
                break;
         }
         for(j=0;j<8;j++)
         {
             if(data&0x80)Show_Pixel(x0,y,0xFF0033);
             x0++;
             data<<=1;
         }
         if(x0-x==size/2)
         {
             x0=x;
             y++;
         }
    }
}

3. 完整示例代码

3.1 中文显示

下面这份代码是单个汉字取模进行显示的，代码较少，整体比较简单。

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/fb.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <string.h>

struct fb_var_screeninfo var;	//可变参数
struct fb_fix_screeninfo fix;	//固定参数
unsigned char *fb_mem=NULL; 	//LCD屏的首地址
extern unsigned char font[];

/* 函数功能: 画点 */
void Show_Pixel(int x,int y,int color) {
	unsigned int *lcd=(unsigned int *)(fb_mem+y*var.xres*var.bits_per_pixel/8+x*var.bits_per_pixel/8);
	*lcd=color; //颜色赋值
}

/* 函数功能: 显示中文 说明: 取模的字体是按照横向取模进行取点阵码。 取模的字体宽度是8的倍数。 */
void ShowFont(int x,int y,int size,unsigned char *data) {
	int i,j,x0=x;
	unsigned char tmp;
	for(i=0;i<size/8*size;i++)
	{
		tmp=data[i];
		for(j=0;j<8;j++)
		{
			if(tmp&0x80)Show_Pixel(x0,y,0xFF0033);
			//else 画背景色
			x0++;
			tmp<<=1;
		}
		if(x0-x==size)
		{
			y++;
			x0=x;
		}
	}
}


int main(int argc,char **argv) {
	int fd=open("/dev/fb0",O_RDWR);
	if(fd<0)
	{
		perror("设备文件打开失败");
		return 0;
	}
	
	/*1. 获取LCD屏的可变形参*/
	ioctl(fd,FBIOGET_VSCREENINFO,&var);
	printf("分辨率:%d*%d\n",var.xres,var.yres);
	printf("像素点位数:%d\n",var.bits_per_pixel);
	
	/*2. 获取LCD屏的固定形参*/
	ioctl(fd,FBIOGET_FSCREENINFO,&fix);
	printf("映射的长度:%d\n",fix.smem_len);
	printf("一行的字节数:%d\n",fix.line_length);
	
	/*3. 映射LCD缓冲区地址到进程空间*/
	fb_mem=mmap(NULL,fix.smem_len,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
	if(fb_mem==NULL)
	{
		perror("空间映射失败!\n");
		return 0;
	}
	
	
	/*4. 控制显示屏*/
	memset(fb_mem,0xFFFFFF,fix.smem_len); //将屏幕清屏为白色
	
	ShowFont(100+0*56,100,56,font);
	ShowFont(100+1*56,100,56,font+7*56*1);
	ShowFont(100+2*56,100,56,font+7*56*2);
	
	munmap(fb_mem,fix.smem_len);
	close(fd);
	return 0;
}


unsigned char font[]=
{ 
/*-- 文字: 嵌 --*/
/*-- 幼圆42; 此字体下对应的点阵为：宽x高=56x56 --*/
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x38,
0x00,0x00,0x00,0x03,0x80,0x00,0x7C,0x00,0x03,0x80,0x07,0xC0,0x00,0x7C,0x00,0x03,
0xC0,0x07,0xC0,0x00,0x7C,0x00,0x03,0xC0,0x07,0xC0,0x00,0x7C,0x00,0x03,0xC0,0x07,
0xC0,0x00,0x7C,0x00,0x03,0xC0,0x07,0xC0,0x00,0x7C,0x00,0x03,0xC0,0x07,0xC0,0x00,
0x7C,0x00,0x03,0xC0,0x07,0xFF,0xFF,0xFF,0xFF,0xFF,0xC0,0x03,0xFF,0xFF,0xFF,0xFF,
0xFF,0x80,0x01,0xFF,0xFF,0xFF,0xFF,0xFF,0x80,0x00,0xFF,0xFF,0xFF,0xFF,0xFC,0x00,
0x00,0x00,0x00,0x00,0x60,0x00,0x00,0x00,0xE0,0x07,0x00,0xF0,0x00,0x00,0x01,0xE0,
0x0F,0x01,0xF0,0x00,0x00,0x01,0xE0,0x0F,0x01,0xF0,0x00,0x00,0x01,0xE0,0x0F,0x01,
0xE0,0x00,0x00,0x01,0xE0,0x0F,0x01,0xE0,0x00,0x00,0x1F,0xFF,0xFF,0xF3,0xFF,0xFF,
0xF0,0x3F,0xFF,0xFF,0xFB,0xFF,0xFF,0xF8,0x3F,0xFF,0xFF,0xFB,0xFF,0xFF,0xF8,0x1F,
0xFF,0xFF,0xE7,0xC3,0x80,0x7C,0x01,0xE0,0x0F,0x07,0x87,0x80,0x7C,0x01,0xE0,0x0F,
0x0F,0x87,0x80,0x7C,0x01,0xE0,0x0F,0x0F,0x87,0x80,0x78,0x01,0xE0,0x0F,0x1F,0x07,
0x80,0x78,0x01,0xE0,0x0F,0x1F,0x07,0x80,0xF8,0x01,0xE0,0x0F,0x3E,0x07,0x80,0xF8,
0x01,0xE0,0x0F,0x3E,0x07,0x80,0xF0,0x01,0xE0,0x0F,0x3C,0x07,0x81,0xF0,0x01,0xE0,
0x0F,0x3C,0x07,0x81,0xE0,0x01,0xE0,0x0F,0x00,0x07,0x83,0xE0,0x01,0xFF,0xFF,0x00,
0x07,0xC3,0xC0,0x01,0xFF,0xFF,0x00,0x07,0xC0,0x00,0x01,0xFF,0xFF,0x00,0x0F,0xE0,
0x00,0x01,0xFF,0xFF,0x00,0x0F,0xE0,0x00,0x01,0xE0,0x0F,0x00,0x0F,0xF0,0x00,0x01,
0xE0,0x0F,0x00,0x1E,0xF0,0x00,0x01,0xE0,0x0F,0x00,0x1E,0xF8,0x00,0x01,0xE0,0x0F,
0x00,0x3E,0x78,0x00,0x01,0xE0,0x0F,0x00,0x7C,0x7C,0x00,0x01,0xE0,0x0F,0x00,0x78,
0x3E,0x00,0x01,0xE0,0x0F,0x00,0xF8,0x1E,0x00,0x01,0xE0,0x0F,0x01,0xF0,0x1F,0x00,
0x01,0xE0,0x0F,0x03,0xE0,0x0F,0x80,0x01,0xE0,0x0F,0x07,0xE0,0x07,0xC0,0x01,0xE0,
0x0F,0x0F,0xC0,0x03,0xE0,0x01,0xE0,0x0F,0x1F,0x80,0x01,0xF0,0x01,0xFF,0xFF,0x3F,
0x00,0x01,0xF8,0x00,0xFF,0xFF,0x7E,0x00,0x00,0xFC,0x00,0x7F,0xFE,0x78,0x00,0x00,
0x3C,0x00,0x00,0x00,0x70,0x00,0x00,0x18,

/*-- 文字: 入 --*/
/*-- 幼圆42; 此字体下对应的点阵为：宽x高=56x56 --*/
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x0F,0x00,0x00,0x00,0x00,0x00,0x00,0x1F,0xC0,0x00,0x00,
0x00,0x00,0x00,0x0F,0xE0,0x00,0x00,0x00,0x00,0x00,0x07,0xF0,0x00,0x00,0x00,0x00,
0x00,0x01,0xF8,0x00,0x00,0x00,0x00,0x00,0x00,0xFC,0x00,0x00,0x00,0x00,0x00,0x00,
0x7C,0x00,0x00,0x00,0x00,0x00,0x00,0x3E,0x00,0x00,0x00,0x00,0x00,0x00,0x1F,0x00,
0x00,0x00,0x00,0x00,0x00,0x1F,0x00,0x00,0x00,0x00,0x00,0x00,0x3F,0x00,0x00,0x00,
0x00,0x00,0x00,0x3F,0x80,0x00,0x00,0x00,0x00,0x00,0x3F,0x80,0x00,0x00,0x00,0x00,
0x00,0x7F,0xC0,0x00,0x00,0x00,0x00,0x00,0x7F,0xC0,0x00,0x00,0x00,0x00,0x00,0x7B,
0xC0,0x00,0x00,0x00,0x00,0x00,0xFB,0xE0,0x00,0x00,0x00,0x00,0x00,0xF1,0xE0,0x00,
0x00,0x00,0x00,0x00,0xF1,0xE0,0x00,0x00,0x00,0x00,0x01,0xF1,0xF0,0x00,0x00,0x00,
0x00,0x01,0xE0,0xF0,0x00,0x00,0x00,0x00,0x03,0xE0,0xF8,0x00,0x00,0x00,0x00,0x03,
0xC0,0xF8,0x00,0x00,0x00,0x00,0x07,0xC0,0x7C,0x00,0x00,0x00,0x00,0x07,0x80,0x7C,
0x00,0x00,0x00,0x00,0x0F,0x80,0x3C,0x00,0x00,0x00,0x00,0x0F,0x00,0x3E,0x00,0x00,
0x00,0x00,0x1F,0x00,0x1E,0x00,0x00,0x00,0x00,0x1E,0x00,0x1F,0x00,0x00,0x00,0x00,
0x3E,0x00,0x0F,0x00,0x00,0x00,0x00,0x7C,0x00,0x0F,0x80,0x00,0x00,0x00,0x7C,0x00,
0x07,0xC0,0x00,0x00,0x00,0xF8,0x00,0x07,0xC0,0x00,0x00,0x01,0xF0,0x00,0x03,0xE0,
0x00,0x00,0x01,0xE0,0x00,0x01,0xE0,0x00,0x00,0x03,0xE0,0x00,0x01,0xF0,0x00,0x00,
0x07,0xC0,0x00,0x00,0xF8,0x00,0x00,0x0F,0x80,0x00,0x00,0xF8,0x00,0x00,0x1F,0x00,
0x00,0x00,0x7C,0x00,0x00,0x1F,0x00,0x00,0x00,0x3E,0x00,0x00,0x3E,0x00,0x00,0x00,
0x3E,0x00,0x00,0x7C,0x00,0x00,0x00,0x1F,0x00,0x00,0xF8,0x00,0x00,0x00,0x0F,0x80,
0x01,0xF0,0x00,0x00,0x00,0x07,0xC0,0x03,0xE0,0x00,0x00,0x00,0x03,0xE0,0x07,0xC0,
0x00,0x00,0x00,0x03,0xF0,0x0F,0x80,0x00,0x00,0x00,0x01,0xF8,0x1F,0x00,0x00,0x00,
0x00,0x00,0xFC,0x1E,0x00,0x00,0x00,0x00,0x00,0x7C,0x1C,0x00,0x00,0x00,0x00,0x00,
0x3C,0x00,0x00,0x00,0x00,0x00,0x00,0x00,

/*-- 文字: 式 --*/
/*-- 幼圆42; 此字体下对应的点阵为：宽x高=56x56 --*/
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x06,0x00,0x00,0x00,0x00,0x00,0x00,0xEF,0x80,0x00,0x00,0x00,0x00,0x01,0xEF,0xE0,
0x00,0x00,0x00,0x00,0x01,0xEF,0xF0,0x00,0x00,0x00,0x00,0x01,0xE3,0xFC,0x00,0x00,
0x00,0x00,0x01,0xE0,0xFF,0x00,0x00,0x00,0x00,0x01,0xF0,0x7F,0x80,0x00,0x00,0x00,
0x01,0xF0,0x1F,0xC0,0x00,0x00,0x00,0x00,0xF0,0x07,0xC0,0x00,0x00,0x00,0x00,0xF0,
0x03,0xC0,0x0F,0xFF,0xFF,0xFF,0xFF,0xFF,0xF0,0x1F,0xFF,0xFF,0xFF,0xFF,0xFF,0xF8,
0x1F,0xFF,0xFF,0xFF,0xFF,0xFF,0xF8,0x0F,0xFF,0xFF,0xFF,0xFF,0xFF,0xF0,0x00,0x00,
0x00,0x00,0xF0,0x00,0x00,0x00,0x00,0x00,0x00,0xF8,0x00,0x00,0x00,0x00,0x00,0x00,
0x78,0x00,0x00,0x00,0x00,0x00,0x00,0x78,0x00,0x00,0x00,0x00,0x00,0x00,0x78,0x00,
0x00,0x00,0x00,0x00,0x00,0x78,0x00,0x00,0x00,0x00,0x00,0x00,0x78,0x00,0x00,0x00,
0x00,0x00,0x00,0x7C,0x00,0x00,0x0F,0xFF,0xFF,0xFE,0x3C,0x00,0x00,0x0F,0xFF,0xFF,
0xFE,0x3C,0x00,0x00,0x0F,0xFF,0xFF,0xFE,0x3C,0x00,0x00,0x00,0x00,0xF0,0x00,0x3C,
0x00,0x00,0x00,0x00,0xF0,0x00,0x3E,0x00,0x00,0x00,0x00,0xF0,0x00,0x3E,0x00,0x00,
0x00,0x00,0xF0,0x00,0x1E,0x00,0x00,0x00,0x00,0xF0,0x00,0x1E,0x00,0x00,0x00,0x00,
0xF0,0x00,0x1E,0x00,0x00,0x00,0x00,0xF0,0x00,0x1F,0x00,0x00,0x00,0x00,0xF0,0x00,
0x0F,0x00,0x00,0x00,0x00,0xF0,0x00,0x0F,0x00,0x00,0x00,0x00,0xF0,0x00,0x0F,0x80,
0x00,0x00,0x00,0xF0,0x00,0x0F,0x80,0x18,0x00,0x00,0xF0,0x00,0x07,0x80,0x3C,0x00,
0x00,0xF0,0x00,0x07,0x80,0x3C,0x00,0x00,0xF0,0x00,0x07,0xC0,0x3C,0x00,0x00,0xF0,
0x00,0x03,0xC0,0x3C,0x00,0x00,0xF0,0x03,0xC3,0xE0,0x3C,0x00,0x00,0xF0,0x1F,0xC1,
0xE0,0x3C,0x00,0x00,0xF1,0xFF,0xC1,0xF0,0x3C,0x00,0x00,0xFF,0xFF,0x01,0xF0,0x3C,
0x00,0x01,0xFF,0xF8,0x00,0xF8,0x3C,0x00,0x0F,0xFF,0x80,0x00,0xF8,0x7C,0x01,0xFF,
0xFC,0x00,0x00,0x7C,0x7C,0x1F,0xFF,0xC0,0x00,0x00,0x3F,0x78,0x3F,0xFC,0x00,0x00,
0x00,0x1F,0xF8,0x3F,0xC0,0x00,0x00,0x00,0x1F,0xF0,0x00,0x00,0x00,0x00,0x00,0x07,
0xF0,0x00,0x00,0x00,0x00,0x00,0x01,0xE0
};

3.2 调用字库显示

单个汉字取模太麻烦，可以使用点阵字库取模软件，然后程序里打开字库，读取字模进行绘制，下面的示例代码就是采用字库读取字模完成汉字显示。

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/fb.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

struct fb_var_screeninfo var;	//可变参数
struct fb_fix_screeninfo fix;	//固定参数
unsigned char *fb_mem=NULL; 	//LCD屏的首地址
unsigned char *fb_GBK=NULL; 	//GBK字库的首地址
extern unsigned char font[];
extern const unsigned char ASCII_16_32[95][64];

/* 函数功能: 画点 */
void Show_Pixel(int x,int y,int color) {
	unsigned int *lcd=(unsigned int *)(fb_mem+y*var.xres*var.bits_per_pixel/8+x*var.bits_per_pixel/8);
	*lcd=color; //颜色赋值
}

/* 函数功能: 显示中文 说明: 取模的字体是按照横向取模进行取点阵码。 取模的字体宽度是8的倍数。 */
void ShowFont(int x,int y,int size,unsigned char *font) {
	unsigned char L,H;
    unsigned int Addr;
    unsigned int font_size=size*size/8; //得到该字节的总字节大小
    unsigned char FontData[128];          //最大可以存放32*32尺寸字体点阵码
	unsigned char *GBK_p; //存放汉字点阵码首地址
    /*计算该汉字在字库里的地址偏移量*/
    L=*(font+1); //低字节
    H=*font;     //高字节
    if(L<0x7f)L=L-0x40;
    else L=L-0x41;
    H=H-0x81;
    Addr=(190*H+L)*font_size; //得到当前汉字在字库里的偏移量
	GBK_p=(unsigned char *)(Addr+fb_GBK); //得到汉字点阵码在字库里首地址
	
	int i,j,x0=x;
	unsigned char tmp;
	for(i=0;i<size/8*size;i++)
	{
		tmp=GBK_p[i];
		for(j=0;j<8;j++)
		{
			if(tmp&0x80)Show_Pixel(x0,y,0xFF0033);
			//else 画背景色
			x0++;
			tmp<<=1;
		}
		if(x0-x==size)
		{
			y++;
			x0=x;
		}
	}
}

/* 函数功能: 显示一个ASCII码。“空格开始 到 ~ 结束” !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ 说明: ASCII码取模 宽度和高度必须是8的倍数，传入的size(高) */
void ShowASCII(int x,int y,int size,unsigned char c_data) {
	int i,j,x0=x;
	unsigned char data;
	int cnt;
	if(c_data<' ' ||  c_data > '~')return; 
	cnt=c_data-' ';
	for(i=0;i<size/2/8*size;i++)
	{
		 switch(size)
		 {
			case 16:
				break;
			 case 32:
				data=ASCII_16_32[cnt][i];
				break;
		 }
		 for(j=0;j<8;j++)
		 {
			 if(data&0x80)Show_Pixel(x0,y,0xFF0033);
			 x0++;
			 data<<=1;
		 }
		 if(x0-x==size/2)
		 {
			 x0=x;
			 y++;
		 }
	}
}


int main(int argc,char **argv) {
	if(argc!=2)
	{
		printf("./app <GBK字库文件>\n");
		return 0;
	}
	
	int fd=open("/dev/fb0",O_RDWR);
	if(fd<0)
	{
		perror("设备文件打开失败");
		return 0;
	}
	
	/*1. 获取LCD屏的可变形参*/
	ioctl(fd,FBIOGET_VSCREENINFO,&var);
	printf("分辨率:%d*%d\n",var.xres,var.yres);
	printf("像素点位数:%d\n",var.bits_per_pixel);
	
	/*2. 获取LCD屏的固定形参*/
	ioctl(fd,FBIOGET_FSCREENINFO,&fix);
	printf("映射的长度:%d\n",fix.smem_len);
	printf("一行的字节数:%d\n",fix.line_length);
	
	/*3. 映射LCD缓冲区地址到进程空间*/
	fb_mem=mmap(NULL,fix.smem_len,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
	if(fb_mem==NULL)
	{
		perror("空间映射失败!\n");
		return 0;
	}
	
	/*4. 映射GBK字库文件到进程空间*/
	int gbk_fb;
	struct stat gbk_buf;
	gbk_fb=open(argv[1],2);
	if(gbk_fb<0)
	{
		perror("GBK字库文件打开失败!");
		return 0;
	}
	stat(argv[1],&gbk_buf);
	printf("GBK字库文件大小=%d\n",gbk_buf.st_size);
	fb_GBK=mmap(NULL,gbk_buf.st_size,PROT_READ,MAP_SHARED,gbk_fb,0);
	if(fb_GBK==NULL)
	{
		perror("空间映射失败!\n");
		return 0;
	}
	
	/*4. 控制显示屏*/
	memset(fb_mem,0xFFFFFF,fix.smem_len); //将屏幕清屏为白色
	
	ShowFont(100+0*32,100,32,"嵌");
	ShowFont(100+1*32,100,32,"入");
	ShowFont(100+2*32,100,32,"式");
	ShowFont(100+3*32,100,32,"开");
	ShowFont(100+4*32,100,32,"发");
	
	ShowASCII(100+0*16,200,32,'A');
	ShowASCII(100+1*16,200,32,'C');
	ShowASCII(100+2*16,200,32,'B');
	
	munmap(fb_mem,fix.smem_len);
	close(fd);
	return 0;
}

今天的文章嵌入式Linux下完成LCD屏文字显示(帧缓冲框架)分享到此就结束了，感谢您的阅读。

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