DESK-MX9-L/Development/How to create a bootable microSD card

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Issue Date Notes
2024/01/31 DESK-MX9-L-5.x.x release



How to create a bootable SD card[edit | edit source]

This article shows how to (re)create the bootable SD card, from the binary images produced by the DESK-MX-L Yocto build, using a standard SD image flasher like balenaEtcher

The process is relatively straightforward: it consists of writing the WIC file of interest generated by Yocto onto the SD card. The following instruction explains how to use balenaEtcher on a Windows host. The procedure is similar when working with a Linux host.

  • download the desired binary image to flash (*.wic or *.wic.bz2) from the mirror binary server selecting the proper DESK-MX9-L release
    • among the binaries made available in the mirror there are several *.wic.bz2 files for the available releases. In particular, there is the dave-image-devel-desk-mx9.wic.bz2 (for AURA) file. This image is the one used to program the microSD card delivered along with the evaluation kit.
  • connect the microSD card to the PC Host
  • open balenaEtcher tool
  • once the tool is open:
    • select the binary to flash by clicking on Flash from file
    • select the microSD to flash by clicking on Select target
    • flash the uSD by clicking o Flash
Unpacking
Flashing
Validating

SD card structure[edit | edit source]

The created SD card has the following structure:

  • raw sectors for the bootloader storage: typically this is an 8MB raw part that stores the bootloader binaries (like imx9_flash.bin) for the bootrom startup
  • FAT32 first partition: this will be mapped to the /dev/mmcblk1p1 device in Linux
    • usually this partition contains the Linux kernel binary and the device tree blob
    • splash screen image is stored in this partition too for a splash image showing during U-Boot startup
  • ext4 second partition: this will be mapped to the /dev/mmcblk1p2 device in Linux
    • this partition contains the Linux root file system

Creating the SD card from binary artifacts[edit | edit source]

Even if the overall binary artifacts have been created by the Yocto build, it is highly discouraged to manually create the SD card starting from them.

The Yocto build takes care of the overall binary consistency (like kernel modules and so on) avoiding mismatching different versions.

Moreover, the SD card is intended to be used during the development process and not for the production phase (where other deployment specifications and details have to be taken into account).


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