Hey Guys,
Recently I tried something really crazy. I m not really good at Java, so I was trying to find out an easy way of displaying an image on frame buffer without having to write a Java program. Here is how it works
Prerequisites:
1. Phone must be rooted.
2. Android platform build setup ready. I have downloaded the Android jellybean 4.1.1 from source.google.com at $PROJECT = /home/jai/NexusS.
create a folder in lcdtest in $PROJECT/external/ and add the following two files
$PROJECT/external/lcdtest/lcdtest1.cpp
$PROJECT/external/lcdtest/Android.mk
lcdtest.cpp looks as follows:
Contents of Android.mk
Now the files are ready. To build the file for Nexus S, first setup the build environment as follows.
Go to $PROJECT directory
Now the build environment is ready. To build the android binary in the shell type
To run this on Nexus, connected the rooted Nexus S device
After phone has restarted:
Good luck and Enjoyy !!!!
Recently I tried something really crazy. I m not really good at Java, so I was trying to find out an easy way of displaying an image on frame buffer without having to write a Java program. Here is how it works
Prerequisites:
1. Phone must be rooted.
2. Android platform build setup ready. I have downloaded the Android jellybean 4.1.1 from source.google.com at $PROJECT = /home/jai/NexusS.
create a folder in lcdtest in $PROJECT/external/ and add the following two files
$PROJECT/external/lcdtest/lcdtest1.cpp
$PROJECT/external/lcdtest/Android.mk
lcdtest.cpp looks as follows:
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
int main()
{
int fbfd = 0;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
long int screensize = 0;
char *fbp = 0;
int x = 0, y = 0;
long int location = 0;
// Open the file for reading and writing
fbfd = open("/dev/graphics/fb0", O_RDWR); //use "/dev/fb0" in linux
if (fbfd == -1) {
perror("Error: cannot open framebuffer device");
exit(1);
}
printf("The framebuffer device was opened successfully.\n");
// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
perror("Error reading fixed information");
exit(2);
}
// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
perror("Error reading variable information");
exit(3);
}
printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
// 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 ( fbp == NULL) {
perror("Error: failed to map framebuffer device to memory");
exit(4);
}
printf("The framebuffer device was mapped to memory successfully.\n");
x = 100; y = 100; // Where we are going to put the pixel
// Figure out where in memory to put the pixel
for (y = 100; y < 200; y++)
for (x = 100; x < 200; x++) {
location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
(y+vinfo.yoffset) * finfo.line_length;
if (vinfo.bits_per_pixel == 32) {
*(fbp + location) = 0;100; //100; // Some blue
*(fbp + location + 1) = 255;//15+(x-100)/2; // A little green
*(fbp + location + 2) = 0;//200-(y-100)/5; // A lot of red
*(fbp + location + 3) = 0; // No transparency
} else { //assume 16bpp
int b = 10;
int g = (x-100)/6; // A little green
int r = 31-(y-100)/16; // A lot of red
unsigned short int t = r<<11 | g << 5 | b;
*((unsigned short int*)(fbp + location)) = t;
}
}
vinfo.activate |= FB_ACTIVATE_NOW | FB_ACTIVATE_FORCE;
if(0 > ioctl(fbfd, FBIOPUT_VSCREENINFO, &vinfo)) {
printf("Failed to refresh\n");
return -1;
}
munmap(fbp, screensize);
close(fbfd);
return 0;
}
Contents of Android.mk
ifneq ($(TARGET_SIMULATOR), true) LOCAL_PATH:= $(call my-dir) include $(CLEAR_VARS) LOCAL_SRC_FILES:=\ lcdtest1.cpp LOCAL_CFLAGS:= -g LOCAL_MODULE:= lcdtest1 LOCAL_MODULE_TAGS := optional include $(BUILD_EXECUTABLE) endif
Now the files are ready. To build the file for Nexus S, first setup the build environment as follows.
Go to $PROJECT directory
$ source build/envsetup.sh $ lunch full_crespo-eng
Now the build environment is ready. To build the android binary in the shell type
$ make -j4 lcdtest1This would create a binary at out/target/product/crespo/system/bin/lcdtest1
To run this on Nexus, connected the rooted Nexus S device
$ adb remount $ adb push out/target/product/crespo/system/bin/lcdtest1 system/lib $ adb reboot
After phone has restarted:
$ adb shell # lcdtest1You would see a green overlay patch as shown.
 |
| Green patch on top of display |
Good luck and Enjoyy !!!!
