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Configure U-Boot Splash Screen

U-Boot Splash Screen

U-Boot can be configured to display a splash screen before the Linux kernel boots. This is typically used to display a product logo.

Enabling the splash screen in U-Boot 2013.10

The AM335x devkit's U-Boot has a branch (u-boot-2013.10) with integrated splash screen support. This branch supports the NEC NL6448BC20-21D, a 640x480 display when connected to the MitySOM-335x Dev Kit baseboard. A sample splash image has been provided. If you are using a custom baseboard and you want to use these instructions, please verify that your pinmux for the display pins matches the MitySOM-335x Dev Kit.

In order to enable the display of the splash screen, please note that you have to uncomment the relevant section of include/configs/mityarm335x.h to define the CONFIG_VIDEO option.

Adding your display configuration

The display driver (DA8xx) needs to be configured to support a specific display.

Display configurations are found at board/cl/mityarm335x/som.c.

For an example see the NEC NL6648BC20-21D's configuration

static const struct da8xx_panel lcd_panel = {
    .name = "640x480",
    .width = 640,
    .height = 480,
    .hfp = 13,
    .hbp = 45,
    .hsw = 63,
    .vfp = 11,
    .vbp = 32,
    .vsw = 2,
    .pxl_clk = 25175000,
    .invert_pxl_clk = 0,
};

LCD Panel configuration fields

Field Description
name Name of the LCD panel. Must be less than 24 characters. This should be in the form of <vendor>_<model> to be descriptive but could be the panel's resolution.
width Width of the panel in pixels.
height Height of the panel in pixels.
hfp Horizontal front porch.
hbp Horizontal back porch.
hsw Horizontal sync pulse width.
vfp Vertical front porch.
vbp Vertical back porch.
vsw Vertical sync pulse width.
pxl_clk Pixel clock frequency.
invert_pxl_clk Set to 1 to invert the pixel clock, 0 otherwise.

This information is provided on the LCD's datasheet although names may differ.

Warning: Running an LCD panel with incorrect clock settings may damage the panel.

Adding your own splash image

U-Boot will automatically pull in a splash image into its binary it builds. To use this feature, the splash image must be added to the tools/logos directory and must have the same name as the build target.
For example, the patch adds a splash image to the mityarm335x board so its image is found at: tools/logos/mityarm335x.bmp

The splash image must be saved as an 8-bit palletized BMP.
This can best be done in Microsoft Paint by saving the image as a "256 Color Bitmap".
Other tools such as ImageMagick's convert may not produce a compatible image.
The image's file type can be checked with the file command:

PC bitmap, Windows 3.x format, 640 x 480 x 8

Make sure the width and height match the screen's resolution and that the bit depth is 8.

Note: Due to the low palette size, images with many colors or gradients may have their colors distorted.

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