Created
May 1, 2011 19:58
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Writing to the frame buffer on a chumby in c
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#include <stdio.h> | |
#include <stdlib.h> | |
#define FRAMESIZE 320*240*2 | |
char * framebuffer; | |
void set_screen(FILE * frame); | |
void set_colour(FILE * frame, char colour[]); | |
void draw_pixel(int x, int y, char * colour); | |
char * rgb_to_byte(int red, int green, int blue); | |
int main() { | |
printf("INFO: Started screen test \n"); | |
// open the framebuffer to read/write | |
FILE * frame = fopen("../../dev/fb0", "r+b"); | |
// make an array size of the framebuffer | |
framebuffer = malloc(sizeof(char)*(FRAMESIZE)); | |
if (frame == NULL) { | |
printf("ERR: Could not access framebuffer \n"); | |
} | |
else { | |
printf("INFO: Created framebuffer \n"); | |
} | |
/** | |
fread(framebuffer, 1, FRAMESIZE, frame); | |
int i; | |
for (i=0; i<FRAMESIZE; i++) { | |
printf("%x \n", framebuffer[i]); | |
}**/ | |
// set background to white | |
char * colour = rgb_to_byte(0, 0, 0); | |
set_colour(frame, colour); | |
// draw line of red | |
int i; | |
for (i=20; i<220; i++) { | |
draw_pixel(160, i, rgb_to_byte(120, 0, 0)); | |
draw_pixel(161, i, rgb_to_byte(120, 0, 0)); | |
} | |
// draw line of cyan | |
int j; | |
for (j=20; j<220; j++) { | |
draw_pixel(165, j, rgb_to_byte(0, 120, 120)); | |
draw_pixel(162, j, rgb_to_byte(0, 120, 120)); | |
} | |
// write array to framebuffer | |
set_screen(frame); | |
fclose(frame); | |
} | |
// writes array to the framebuffer | |
void set_screen(FILE * frame) { | |
rewind(frame); | |
fwrite(framebuffer, 1, FRAMESIZE, frame); | |
} | |
// sets the entire frame buffer to colour | |
void set_colour(char colour[]) { | |
int i; | |
for (i=0; i<(320*240*2); i=i+2) { | |
framebuffer[i] = colour[0]; | |
int j = i; | |
j++; | |
framebuffer[j] = colour[1]; | |
} | |
} | |
// converts rgb to byte | |
char * rgb_to_byte(int red, int green, int blue) { | |
short int colour16 = (short)(((blue&0xf8)<<8) + | |
((red&0xfc)<<3) + ((green&0xf8)>>3)); | |
char * arr = malloc(sizeof(char)*2); | |
arr[0] = ((colour16 >> 8) & 0xff); | |
arr[1] = ((colour16 >> 0) & 0xff); | |
return arr; | |
} | |
// sets a single pixel to colour | |
void draw_pixel(int x, int y, char * colour) { | |
int pos = (((320*y)+x)*2); | |
framebuffer[pos] = colour[0]; | |
framebuffer[pos+1] = colour[1]; | |
} |
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cool!