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This application note explains how to show a static splash image on the display immediately after power-on / reboot. This feature can be used to indicate to the user that the device is alive and running, while the system still continues to boot up.

1. Understanding Static Splash Image Implementation

1.1. U-Boot Display Driver

The existing U-Boot STM32 LTDC driver (drivers/video/stm32/stm32_ltdc.c) is used to provide support for displaying a splash screen image on the display. By default, the U-Boot LCD display is configured to support the 480x272 resolution. Only true color (24 bpp) images can be displayed by U-Boot. Format of the splash screen image is "PC bitmap, Windows 3.x format, 480 x 272 x 24".

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&ltdc {
        status = "okay";
        pinctrl-0 = <&ltdc_pins>;
        display-timings {
                timing@0 {
                        clock-frequency = <12000000>;
                        hactive = <480>;
                        vactive = <272>;
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1.2. U-Boot Splash Image

The stm32h7-splash-24bpp.bmp splash image stored in board/emcraft/stm32h7-som in the U-Boot source tree is used as the default image to be displayed.

2. Manipulating Splash Image

2.1. Installation Script

The system installation kermit script stm32h7-som-prog.kermit allows to write the splash image to the dedicated UBI volume on the QSPI Flash system partition.

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1. From the U-Boot command interface, call the loadb command to load a splash image to SDRAM from the development host via UART using the kermit utility.

2. From the U-Boot command interface, call the ubi write $loadaddr splash $filesize command to copy splash image from SDRAM to the QSPI NAND Flash.

2.2. Updating Splash Image

Perform the following step-wise procedure to update a splash image on the STM32H7 SOM:

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