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 1.5.11 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 USB type-C cable to your development PC and the other end to the target USB type-C 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-2023.04-r3.2 (Jan 30 2024 - 10:57:23 +0000)
SOC: 0xa1009300
LC: 0x2040010
PMIC: Over Drive Voltage Mode
M33 prepare ok
Normal Boot
Trying to boot from BOOTROM
Boot Stage: Primary boot
image offset 0x0, pagesize 0x200, ivt offset 0x0
Load image from 0x4f400 by ROM_API
NOTICE:  BL31: v2.8(release):lf-6.1.55-2.2.0-0-g08e9d4eef226-dirty
NOTICE:  BL31: Built : 16:47:44, Jan 30 2024


U-Boot dub-2023.04-r3.2 (Jan 30 2024 - 10:57:23 +0000)

CPU:   i.MX93(52) rev1.1 1700 MHz (running at 1692 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 42C
Reset cause: POR (0x1)
DRAM:  992 MiB
Core:  202 devices, 29 uclasses, devicetree: separate
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
In:    serial
Out:   serial
Err:   serial
Model: Digi ConnectCore 93 Development Kit
ConnectCore 93 SOM variant 0x01: 992 MiB LPDDR4, Wi-Fi, Bluetooth
Boot:  MMC0

BuildInfo:
  - ELE firmware version 0.1.0-44880904

flash target is MMC:0
Net:   eth0: ethernet@428a0000 [PRIME]
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 1

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

    $ cd tmp/deploy/images/ccimx93-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.
   -n                     No wait. Skips 10 seconds delay to stop script.
   -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.