AM335X用RGB888连接LCD如何以16位色彩模式显示图片

Posted 2020-10-10 bigmagic

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

 

<wiz_tmp_tag id="wiz-table-range-border" contenteditable="false" style="display: none;">