LCD应用程序测试

最新推荐文章于 2021-05-09 04:53:16 发布

weixin_30538029

最新推荐文章于 2021-05-09 04:53:16 发布

阅读量390

点赞数

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/linux-37ge/p/10212540.html

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)        ;
    }
}