[技术]

【飞凌T507开发板试用体验】基于FrameBuffer的LCD显示测试(内有避坑提示)

jf_1137202360

2022-11-9 16:24:17 2536

rgb刷屏

前言

GUI的开发可以有多种方式,比如使用Qt等,而Linux下的Framebuffer可直接类似于操作显存的方式直接写点的颜色,更简单直接,开发环境也更简单,不需要像Qt一样搭建比较复杂的开发环境。所以我们先从简单开始测试下基于Framebuffer的LCD显示,后面基于该方式进行GUI程序的开发。

过程

基于Frambebuffer开发只需要安装编译器即可,环境搭建很简单,

安装GCC编译器

sudo apt-get install gcc-aarch64-linux-gnu

查看编译器版本

aarch64-linux-gnu-gcc -v

编写代码framebuffer.c如下

#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/fb.h>
int main(int argc, char *argv[])
{
    int fd = -1;
    int ret = -1;
    uint8_t *p_fb = 0;
    struct fb_fix_screeninfo finfo;
    struct fb_var_screeninfo vinfo;
    memset(&finfo,0,sizeof(finfo));
    memset(&vinfo,0,sizeof(vinfo));
    fd = open(argv[1],O_RDWR);
    if(fd < 0)
    {
        fprintf(stderr,"open %s err, %s\n",argv[1],strerror(errno));
        return -1;
    }
    ret = ioctl(fd, FBIOGET_FSCREENINFO, &finfo);
    if(ret < 0)
    {
        fprintf(stderr,"ioctl finfo err, %s\n",strerror(errno));
        close(fd);
        return -1;
    }
    ret = ioctl(fd, FBIOGET_VSCREENINFO, &vinfo);
    if(ret < 0)
    {
        fprintf(stderr,"ioctl vinfo err, %s\n",strerror(errno));
        close(fd);
        return -1;
    }

    vinfo.yoffset = 0;
    ret = ioctl(fd, FBIOPAN_DISPLAY, &vinfo);
    if(ret < 0)
    {
        fprintf(stderr,"ioctl vinfo err, %s\n",strerror(errno));
        close(fd);
        return -1;
    }

    unsigned long len = vinfo.xres_virtual  * vinfo.yres_virtual * vinfo.bits_per_pixel / 8;
    p_fb = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if(p_fb == NULL)
    {
        fprintf(stderr,"mmap len %ld err\n",len);
        close(fd);
        return -1;
    }
    //fprintf(stderr,"x = %d y = %d vx = %d vy = %d bits = %d len = %ld\n",vinfo.xres,vinfo.yres,vinfo.xres_virtual,vinfo.yres_virtual,vinfo.bits_per_pixel,len);
    fprintf(stderr,"x = %d, y = %d\r\n",vinfo.xres,vinfo.yres);
    fprintf(stderr,"vx = %d, vy = %d\r\n",vinfo.xres_virtual,vinfo.yres_virtual);
    fprintf(stderr,"ox = %d, oy = %d\r\n",vinfo.xoffset,vinfo.yoffset);
    fprintf(stderr,"bits = %d\r\n",vinfo.bits_per_pixel);
    fprintf(stderr,"gray = %d\r\n",vinfo.grayscale);
    fprintf(stderr,"red offset:%d length:%d msb_right:%d\r\n",vinfo.red.offset,vinfo.red.length,vinfo.red.msb_right);
    fprintf(stderr,"green offset:%d length:%d msb_right:%d\r\n",vinfo.green.offset,vinfo.green.length,vinfo.green.msb_right);  
    fprintf(stderr,"blue offset:%d length:%d msb_right:%d\r\n",vinfo.blue.offset,vinfo.blue.length,vinfo.blue.msb_right);  
    fprintf(stderr,"transp offset:%d length:%d msb_right:%d\r\n",vinfo.transp.offset,vinfo.transp.length,vinfo.transp.msb_right); 
    
    volatile int times = 30;
    while(times--)
    {
        if(vinfo.bits_per_pixel == 16)
        {
            for(unsigned int i=0; i< len; )
            {
                *((uint16_t*)(p_fb + i)) = 0xF800;
                i+=2;
            }
            usleep(atoi(argv[2])*1000);
            for(unsigned int i=0; i< len;)
            {
                *((uint16_t*)(p_fb + i)) = 0x07E0;
                i+=2;
            }
            usleep(atoi(argv[2])*1000);
            for(unsigned int i=0; i< len;)
            {
                *((uint16_t*)(p_fb + i)) = 0x001F;
                i+=2;
            }
            usleep(atoi(argv[2])*1000);
        }
        else
        {
            for(unsigned int i=0; i< len;)
            {
                *((uint32_t*)(p_fb + i)) = 0xFFFF0000;
                i+=4;
            }
            usleep(atoi(argv[2])*1000);
            for(unsigned int i=0; i< len;)
            {
                *((uint32_t*)(p_fb + i)) = 0xFF00FF00;
                i+=4;
            }
            usleep(atoi(argv[2])*1000);
            for(unsigned int i=0; i< len;)
            {
                *((uint32_t*)(p_fb + i)) = 0xFF0000FF;
                i+=4;
            }
            usleep(atoi(argv[2])*1000);
        }
    }
    munmap(p_fb,len);
    close(fd);
    return 0;
}

编译代码

aarch64-linux-gnu-gcc framebuffer.c -o framebuffer

将代码通过串口rz导入到开发板

将代码添加可执行权限

chmod +x framebuffer

运行

./framebuffer /dev/fb0 1000

打印了一些fb_var_screeninfo信息

root@forlinx:/# ./framebuffer /dev/fb0 1000

x = 1024, y = 600

vx = 1024, vy = 1200

ox = 0, oy = 0

bits = 32

gray = 0

red offset:16 length:8 msb_right:0

green offset:8 length:8 msb_right:0

blue offset:0 length:8 msb_right:0