displaying to TRDB_LCM

i'm doing my project where i need to read the JPEG file from sd card and then display it to lcd screen TRDB_LCM. i've been able to read the data and decompressed it. so now i have to display them. i use the sdram as the buffer. so i use vga controller core, pixel buffer core, and sdram controller core. i set the memory buffer start address to sdram controller base address.

and to test it, i use the code below:

alt_up_pixel_buffer_dev * pixel_buf_dev;

// open the Pixel Buffer port

//pixel_buf_dev = alt_up_pixel_buffer_open_dev ("/dev/pixel_buffer");

if ( pixel_buf_dev == NULL)

alt_printf ("Error: could not open pixel buffer device \n");

else

alt_printf ("Opened pixel buffer device \n");

/* Clear and draw a blue box on the screen */

alt_up_pixel_buffer_clear_screen (pixel_buf_dev, 0);

volatile int i =0;

volatile int j =0;

volatile int cnt =0;

while(1){

if(cnt==50000){

if(j==200){

j=0;

i+=20;

}

if(i==200)i=0;

//

alt_up_pixel_buffer_clear_screen (pixel_buf_dev, 0);

alt_up_pixel_buffer_draw_box (pixel_buf_dev, j, 10, i, 10, 0xf01F, 0);

j++;

cnt = 0;

}

cnt++;

}

but there's nothing displayed on the screen, just all white.

i dont know what's wrong. do i have to store the RGB data to sdram first?? are there any other configurations need to be done??

thanks before