前言
基于framebuffer快速对hdmi输出进行测试，以下都是直接串口终端登录开发板，使用开发板自己的编译工具链进行编译，无需交叉编译非常方便。
代码新建fb.c
vi fb.c
输入如下内容
#include <unistd.h>#include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <linux/fb.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <stdint.h> int main(int argc, char *argv[]) { int fbfd = 0; struct fb_var_screeninfo vinfo; unsigned long screensize = 0; unsigned long location = 0; char *fbp = 0; int x = 0, y = 0; int seg_len = 0; int tmp_seg_len = 0; int seg_num = 0; uint32_t rgb = 0; uint32_t r = 0, g = 0, b = 0; // Open the file for reading and writing fbfd = open("/dev/fb0", O_RDWR); if (!fbfd) { printf("Error: cannot open framebuffer device.\n"); exit(1); } printf("The framebuffer device was opened successfully.\n"); // Get variable screen information if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) { printf("Error reading variable information.\n"); exit(1); } printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel); //if (vinfo.bits_per_pixel != 16) { // printf("Error: not supported bits_per_pixel, it only supports 16 bit color\n"); // exit(1); //} // Figure out the size of the screen in bytes screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel/8; // Map the device to memory fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0); if ((int)fbp == -1) { printf("Error: failed to map framebuffer device to memory.\n"); exit(4); } printf("The framebuffer device was mapped to memory successfully.\n"); seg_len = vinfo.yres/6; #if 1 seg_len = vinfo.yres/6; for (seg_num = 0; seg_num < 6; seg_num++) { if (seg_num == 5) tmp_seg_len = vinfo.yres - seg_len*5; else tmp_seg_len = seg_len; for (y = 0; y < tmp_seg_len; y++) { for (x = 0; x < vinfo.xres; x++) { location = seg_num*seg_len*vinfo.xres*vinfo.bits_per_pixel/8 + (y*vinfo.xres+ x)*vinfo.bits_per_pixel/8; switch (seg_num) { case 0: r = 0xff; g = (0xff/seg_len)*y; b = 0; break; case 1: r = (0xff/seg_len)*(seg_len-y); g = 0xff; b = 0; break; case 2: r = 0; g = 0xff; b = (0xff/seg_len)*y; break; case 3: r = 0; g = (0xff/seg_len)*(seg_len-y); b = 0xff; break; case 4: r = (0xff/seg_len)*y; g = 0; b = 0xff; break; case 5: r = 0xff; b = (0xff/seg_len)*(seg_len-y); g = 0; break; default: printf("%s--%d:unknown seg_num %d\n", __FILE__, __LINE__); break; } if(vinfo.bits_per_pixel == 16) { r = (r*0x1f)/0xff; g = (g*0x3f)/0xff; b = (b*0x1f)/0xff; rgb = (r << 11) | (g << 5) | b; *((uint16_t*)(fbp + location)) = rgb; } else { rgb = (r << 16) | (g << 8) | b; *((uint32_t*)(fbp + location)) = rgb; } } } } sleep(2); seg_len = vinfo.yres/6; for (seg_num = 0; seg_num < 6; seg_num++) { if (seg_num == 5) tmp_seg_len = vinfo.yres - seg_len*5; else tmp_seg_len = seg_len; for (y = 0; y < tmp_seg_len; y++) { for (x = 0; x < vinfo.xres; x++) { location = seg_num*seg_len*vinfo.xres*vinfo.bits_per_pixel/8 + (y*vinfo.xres+ x)*vinfo.bits_per_pixel/8; switch (seg_num) { case 0://grey r = 100; g = 100; b = 100; break; case 1: //black r = 0x00; g = 0x00; b = 0x00; break; case 2://white r = 0xff; g = 0xff; b = 0xff; break; case 3://red r = 0xff; g = 0; b = 0; break; case 4: //green r = 0; g = 0xff; b = 0; break; case 5: //blue r = 0; g = 0; b = 0xff; break; default: printf("%s--%d:unknown seg_num %d\n", __FILE__, __LINE__); break; } if(vinfo.bits_per_pixel == 16) { r = (r*0x1f)/0xff; g = (g*0x3f)/0xff; b = (b*0x1f)/0xff; rgb = (r << 11) | (g << 5) | b; *((uint16_t*)(fbp + location)) = rgb; } else { rgb = (r << 16) | (g << 8) | b; *((uint32_t*)(fbp + location)) = rgb; } } } } #endif #if 1 sleep(2); seg_len = vinfo.xres/6; for (seg_num = 0; seg_num < 6; seg_num++) { if (seg_num == 5) tmp_seg_len = vinfo.xres - seg_len*5; else tmp_seg_len = seg_len; for (x = 0; x < tmp_seg_len; x++) { for (y = 0; y < vinfo.yres; y++) { location = y*vinfo.xres*vinfo.bits_per_pixel/8 + (seg_num*seg_len + x)*vinfo.bits_per_pixel/8; switch (seg_num) { case 0: r = 0xff; g = (0xff/seg_len)*x; b = 0; break; case 1: r = (0xff/seg_len)*(seg_len-x); g = 0xff; b = 0; break; case 2: r = 0; g = 0xff; b = (0xff/seg_len)*x; break; case 3: r = 0; g = (0xff/seg_len)*(seg_len-x); b = 0xff; break; case 4: r = (0xff/seg_len)*x; g = 0; b = 0xff; break; case 5: r = 0xff; g = 0; b = (0xff/seg_len)*(seg_len-x); break; default: printf("%s--%d:unknown seg_num %d\n", __FILE__, __LINE__); break; } if(vinfo.bits_per_pixel == 16) { r = (r*0x1f)/0xff; g = (g*0x3f)/0xff; b = (b*0x1f)/0xff; rgb = (r << 11) | (g << 5) | b; *((uint16_t*)(fbp + location)) = rgb; } else { rgb = (r << 16) | (g << 8) | b; *((uint32_t*)(fbp + location)) = rgb; } } } } sleep(2); seg_len = vinfo.xres/6; /* white black gray red green blue */ for (seg_num = 0; seg_num < 6; seg_num++) { if (seg_num == 5) tmp_seg_len = vinfo.xres - seg_len*5; else tmp_seg_len = seg_len; for (x = 0; x < tmp_seg_len; x++) { for (y = 0; y < vinfo.yres; y++) { location = y*vinfo.xres*vinfo.bits_per_pixel/8 + (seg_num*seg_len + x)*vinfo.bits_per_pixel/8; switch (seg_num) { case 0://grey r = 100; g = 100; b = 100; break; case 1://black r = 0; g = 0; b = 0; break; case 2: //white r = 0xff; g = 0xff; b = 0xff; break; case 3://red r = 0xff; g = 0; b = 0; break; case 4: //green r = 0; g = 0xff; b = 0; break; case 5: //blue r = 0; g = 0; b = 0xff; break; default: printf("%s--%d:unknown seg_num %d\n", __FILE__, __LINE__); break; } if(vinfo.bits_per_pixel == 16) { r = (r*0x1f)/0xff; g = (g*0x3f)/0xff; b = (b*0x1f)/0xff; rgb = (r << 11) | (g << 5) | b; *((uint16_t*)(fbp + location)) = rgb; } else { rgb = (r << 16) | (g << 8) | b; *((uint32_t*)(fbp + location)) = rgb; } } } } #endif munmap(fbp, screensize); close(fbfd); return 0; }
复制代码gcc -o3 fb.c -o fb
运行先登录桌面wetson,桌面终端中输入init 1,关闭图形桌面
(串口终端中输入init 5可恢复桌面）
./fb
效果如下
/4 
