[U-Boot] Displaying characters on the display in u-boot

[Bhargav A K]

Hi

> Why are you using 0xA5000000 address here as the frame buffer base
> address?

Yeah this is a very much a valid frame buffer address. I 'used' to use this for splash screen also and it
worked fine.

>  Can you see changes on the display if you write data to this address by
> U-Boot "mw" command (i.e. "mw a5000000 ffffffff 100") ?

No.. but the memory will have all "f"'s contained in it until I reboot.

> Probably the frame buffer or display controller configuration is
> wrong then. Is the display backlight enabled?

Frame buffer configuration has to be right.. it worked for the splash screen
Is it any different for text displaying ?

Yeah, backlight is enabled.

> lcd_drawchars() will not help since you do not use the lcd driver.

I displayed the bmp images on the LCD, which I had been asking u in the
'u-boot.10912.n7.nabble.com' forum.
The method I used goes like this,
- I created a gzip of the bmp
- used the xxd -i to create a HEX dump of it.
- made it part of the u-boot compilation process, that was a requirement imposed.
- gunzip it runtime, just use a portion of lcd_display_bitmap, which does the conversion
  to RGB888. The portion of the code where bmp_bpix=32, in the switch case.
- its just too good, the u-boot.bin is 330 KB with more that 15 images inside it :D
- my u-boot just became awesome after that.

On the same lines, I tried using lcd_drawchars(). Please correct me if I'm wrong.

But the bigger problem here is I'm not able to figure out where the mistake is.
I'm pretty conversant with using the Lauterbach to debug. I have JTAG pins drawn out on my board.

Please give me Ur suggestions.

Regards
Bhargav
________________________________________
From: Anatolij Gustschin [agust at denx.de]
Sent: Sunday, April 28, 2013 7:52 PM
To: Bhargav A K
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] Displaying characters on the display in u-boot

Hi,

On Fri, 19 Apr 2013 21:29:33 +0530
Bhargav A K <bhargav.ak at sasken.com> wrote:

> Hi All,
>
> I have enabled the following configurations.
> in my board's config header
>
> #define CONFIG_VGA_AS_SINGLE_DEVICE
> #define CONFIG_VIDEO
> #define CONFIG_CFB_CONSOLE
>
> video_hw_init() returns a pointer to GraphicsDevice structure.
>
> It does the following
> -----------------------------------------------------
> omap4_GD.winSizeX = 480; //__raw_readl()
> omap4_GD.winSizeY = 800;
> omap4_GD.gdfBytesPP = 4;
> omap4_GD.gdfIndex = GDF_32BIT_X888RGB;
>
> __raw_writel(0xA5000000, DISPC_GFX_BA0);
> omap4_GD.frameAdrs = __raw_readl(DISPC_GFX_BA0);

Why are you using 0xA5000000 address here as the frame buffer base
address? Are you sure that this is a valid memory address? Can you
see changes on the display if you write data to this address by
U-Boot "mw" command (i.e. "mw a5000000 ffffffff 100") ?
Which frame buffer base address did you use before for working
splashscreen?

> initDisplay(); // Do all other clocks, GPIOs, OMAP4 registers specific for LCD(DSI, DISPC, DSS).
> ------------------------------------------------------
>
> board_video_init() is just a dummy call.
>
> I did a console_assign() to redirect stderr and stdout to vga.
> All the printf's doesn't come on the serial console or the LCD.
>
> I tried using the video_drawstring(10, 20, "hello world"),
> after resetting the stdout to serial. I see all the "printf's" on the
> serial console, but the string from video_drawstring()(hello world)
> won't come on the LCD even after syncing LCD pipelines (GO_LCD in OMAP4470).

Probably the frame buffer or display controller configuration is
wrong then. Is the display backlight enabled?

> Then I just exported the lcd_drawchars() function into my LCD code,
> tried to write characters to the LCD, nothing came onto the screen.

lcd_drawchars() will not help since you do not use the lcd driver.

Thanks,

Anatolij

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