AM335X用RGB888连接LCD如何以16位色彩模式显示图片

在AM335x中，在连接显示屏的时候，存在一个问题。这个在am335x Sillicon Errata已经提到过在RGB888模式中

 而对于RGB565模式的硬件连接

不难看出，这个RGB是反的。看一下我们自己硬件的连接方式我们自己的硬件连接是RGB888

在模式设置成32位真彩显示时没有问题，但是一旦把32位换成32位时，就会发现图片的颜色显示异常。换一张纯色的红色bmp图片到开发板上，显示成蓝色。效果如图

   那么如何让RGB888的硬件连接也能正常显示16位呢？ 第一步：首先将开发板的bpp从32位改成16位 

  接下来修改驱动程序da8xx-fb.c修改函数fb_check_var 实际上就是将红色与蓝色调换一下 

static int fb_check_var(struct fb_var_screeninfo *var,
struct fb_info *info)
{
int err = 0;
struct da8xx_fb_par *par = info->par;
int bpp = var->bits_per_pixel >> 3;
unsigned long line_size = var->xres_virtual * bpp;switch (var->bits_per_pixel) {
case 1:
case 8:
var->red.offset = 0;
var->red.length = 8;
var->green.offset = 0;
var->green.length = 8;
var->blue.offset = 0;
var->blue.length = 8;
var->transp.offset = 0;
var->transp.length = 0;
break;
case 4:
var->red.offset = 0;
var->red.length = 4;
var->green.offset = 0;
var->green.length = 4;
var->blue.offset = 0;
var->blue.length = 4;
var->transp.offset = 0;
var->transp.length = 0;
break;
case 16:/* RGB 565 */
var->red.offset = 11;  //改成var->blue.offset = 11;
var->red.length = 5;   //改成var->blue.length = 5;
var->green.offset = 5;
var->green.length = 6;
var->blue.offset = 0;  //改成var->red.offset = 0;
var->blue.length = 5;  //改成var->red.length = 5;
var->transp.offset = 0;
var->transp.length = 0;
break;
case 24:
var->red.offset = 16;
var->red.length = 8;
var->green.offset = 8;
var->green.length = 8;
var->blue.offset = 0;
var->blue.length = 8;
break;
case 32:
var->transp.offset = 24;
var->transp.length = 8;
var->red.offset = 16;
var->red.length = 8;
var->green.offset = 8;
var->green.length = 8;
var->blue.offset = 0;
var->blue.length = 8;
break;
default:
err = -EINVAL;
}var->red.msb_right = 0;
var->green.msb_right = 0;
var->blue.msb_right = 0;
var->transp.msb_right = 0;if (line_size * var->yres_virtual > par->vram_size)
var->yres_virtual = par->vram_size / line_size;if (var->yres > var->yres_virtual)
var->yres = var->yres_virtual;if (var->xres > var->xres_virtual)
var->xres = var->xres_virtual;if (var->xres + var->xoffset > var->xres_virtual)
var->xoffset = var->xres_virtual - var->xres;
if (var->yres + var->yoffset > var->yres_virtual)
var->yoffset = var->yres_virtual - var->yres;return err;
}

–  

x

   1

static int fb_check_var(struct fb_var_screeninfo *var,

2

struct fb_info *info)

3

{

4

int err = 0;

5

struct da8xx_fb_par *par = info->par;

6

int bpp = var->bits_per_pixel >> 3;

7

unsigned long line_size = var->xres_virtual * bpp;

8

9

switch (var->bits_per_pixel) {

10

case 1:

11

case 8:

12

var->red.offset = 0; 

13

var->red.length = 8; 

14

var->green.offset = 0;

15

var->green.length = 8;

16

var->blue.offset = 0;

17

var->blue.length = 8;

18

var->transp.offset = 0;

19

var->transp.length = 0;

20

break;

21

case 4:

22

var->red.offset = 0;

23

var->red.length = 4;

24

var->green.offset = 0;

25

var->green.length = 4;

26

var->blue.offset = 0;

27

var->blue.length = 4;

28

var->transp.offset = 0;

29

var->transp.length = 0;

30

break;

31

case 16:/* RGB 565 */

32

var->red.offset = 11;  //改成var->blue.offset = 11;

33

var->red.length = 5;   //改成var->blue.length = 5; 

34

var->green.offset = 5;

35

var->green.length = 6;

36

var->blue.offset = 0;  //改成var->red.offset = 0; 

37

var->blue.length = 5;  //改成var->red.length = 5;

38

var->transp.offset = 0;

39

var->transp.length = 0;

40

break;

41

case 24:

42

var->red.offset = 16;

43

var->red.length = 8;

44

var->green.offset = 8;

45

var->green.length = 8;

46

var->blue.offset = 0;

47

var->blue.length = 8;

48

break;

49

case 32:

50

var->transp.offset = 24;

51

var->transp.length = 8;

52

var->red.offset = 16;

53

var->red.length = 8;

54

var->green.offset = 8;

55

var->green.length = 8;

56

var->blue.offset = 0;

57

var->blue.length = 8;

58

break;

59

default:

60

err = -EINVAL;

61

}

62

63

var->red.msb_right = 0;

64

var->green.msb_right = 0;

65

var->blue.msb_right = 0;

66

var->transp.msb_right = 0;

67

68

if (line_size * var->yres_virtual > par->vram_size)

69

var->yres_virtual = par->vram_size / line_size;

70

71

if (var->yres > var->yres_virtual)

72

var->yres = var->yres_virtual;

73

74

if (var->xres > var->xres_virtual)

75

var->xres = var->xres_virtual;

76

77

if (var->xres + var->xoffset > var->xres_virtual)

78

var->xoffset = var->xres_virtual - var->xres;

79

if (var->yres + var->yoffset > var->yres_virtual)

80

var->yoffset = var->yres_virtual - var->yres;

81

82

return err;

83

}

  这样就能在开发板上正常显示颜色了

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