void showButton(int yPlace, int xPlace){        // y = x && x = y
    short int file_handle, i, j, x, y;
    int color;
    file_handle = alt_up_sd_card_fopen("knopje.bmp", 0);
    if (file_handle >= 0) {

        // Skip header data
        short int read_byte;
        for(i = 0; i < 54 ; i++) {
            read_byte = alt_up_sd_card_read(file_handle);
        }

        // Read image
        for(j = 0; j < 16; j++) {
            for(i = 0; i < 16; i++) {
                read_byte = alt_up_sd_card_read(file_handle);
                x = read_byte;
                if( read_byte == -1 ) {
                    printf("no bytes to read\n");
                    break;
                }
                read_byte = alt_up_sd_card_read(file_handle);
                y = read_byte;
                color =  (x << 8) | y;
                //color =  x | (y << 8);
                //if (color != 0) printf("Color = %x\n", color);
                *(pixel_buffer + ((xPlace-j) << 9) + (i + yPlace)) = (unsigned int) color;
            }
        }
    } else {
        printf("Can't open button image\n");
    }
    alt_up_sd_card_fclose(file_handle);
}