Fastboot is a protocol for communication between your device and a computer. It allows you to modify file system images over a USB connection, which is a quick way to update firmware during development. Fastboot requires the USB interface to work as 'device'.

Although it was originally developed for Android images, its implementation on the NXP UUU (Universal Update Utility) tool extends the functionality to any file type.

To update U-Boot via USB OTG using uuu and the Fastboot protocol:

  1. Download the latest Universal Update Utility (UUU), a software tool from NXP.

    UUU version should be v1.5.11 or higher.

  2. Place the uuu executable in a directory in your PATH, such as /usr/bin.

  3. Install udev rules to allow any user to run uuu to access the USB port:

    $ sudo sh -c "uuu -udev >> /etc/udev/rules.d/70-uuu.rules"
$ sudo udevadm control --reload

  4. Connect a micro USB cable to your development PC and the other end to the target USB recovery connector.

  5. Reset the device by pressing the reset button on the board and immediately press any key in the serial terminal to stop the auto-boot process. The U-Boot bootloader prompt displays:

    U-Boot SPL dub-2020.04-r6.1 (Sep 19 2023 - 07:19:27 +0000)
DDRINFO: start DRAM init
DDRINFO: DRAM rate 3000MTS
DDRINFO:ddrphy calibration done
DDRINFO: ddrmix config done
Normal Boot
Trying to boot from MMC2
NOTICE:  BL31: v2.4(release):lf-5.10.72-2.2.3-2-gb67eb4618
NOTICE:  BL31: Built : 07:19:48, Sep 19 2023


U-Boot dub-2020.04-r6.1 (Sep 19 2023 - 07:19:27 +0000)

CPU:   i.MX8MMQ rev1.0 1600 MHz (running at 1200 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 32C
Reset cause: POR
DRAM:  2 GiB
MCA:   HW_VER=1  FW_VER=1.00
MMC:   FSL_SDHC: 1, FSL_SDHC: 0
In:    serial
Out:   serial
Err:   serial
Model: Digi ConnectCore 8M Mini Development Kit
ConnectCore 8M Mini SOM variant 0x03: 2 GiB LPDDR4, Wi-Fi, Bluetooth, MCA, Crypto-auth
  Board version 3, ID undefined
Boot:  MMC2

 BuildInfo:
  - ATF b67eb46
  - U-Boot dub-2020.04-r6.1

flash target is MMC:0
Net:   eth0: ethernet@30be0000
Fastboot: Normal
Normal Boot
Hit any key to stop autoboot:  0
=>
    Information in the console log may vary.

  6. On the target, in U-Boot, execute the following command:

    => fastboot 0

  7. On your development PC, change to your Digi Embedded Yocto project’s deploy images folder:

    $ cd tmp/deploy/images/ccimx8mm-dvk/

  8. Run the install_linux_fw_uuu.sh script with -h parameter to check the syntax:

    $ ./install_linux_fw_uuu.sh -h
############################################################
#           Linux firmware install through USB OTG         #
############################################################
Usage: ./install_linux_fw_uuu.sh [options]

  Options:
   -b                     Activate bootcount mechanism (3 boot attempts).
   -d                     Install firmware on dualboot partitions (system A and system B).
                          (Implies -b).
   -h                     Show this help.
   -i <dey-image-name>    Image name that prefixes the image filenames, such as 'dey-image-qt',
                          'dey-image-webkit', 'core-image-base'...
                          Defaults to 'dey-image-qt' if not provided.
   -k <dek-filename>      Update includes dek file.
                          (implies -t)."
   -n                     No wait. Skips 10 seconds delay to stop script.
   -t                     Install TrustFence artifacts.
   -u <u-boot-filename>   U-Boot filename.
                          Auto-determined by variant if not provided.

  9. To program the default image files (dey-image-qt):

    $ ./install_linux_fw_uuu.sh

  10. Once the firmware is installed, the device boots automatically. The default username is root with no password.