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 micro USB cable to your development PC and the other end to the target USB OTG 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:

    NOTICE:  CPU: STM32MP157CAC Rev.Z
NOTICE:  Model: Digi International ConnectCore MP15 Development Kit
NOTICE:  BL2: v2.6-stm32mp1-r1.0(release):dub-2021.10-r1.1
NOTICE:  BL2: Built : 13:07:24, Nov  4 2022
NOTICE:  BL2: Booting BL32
optee optee: OP-TEE: revision 3.16 (9f1b4813)


U-Boot dub-2021.10-r1.1 (Nov 04 2022 - 13:58:26 +0100)

CPU: STM32MP157CAC Rev.Z
DRAM:  512 MiB
optee optee: OP-TEE: revision 3.16 (9f1b4813)
Clocks:
- MPU : 650 MHz
- MCU : 208.878 MHz
- AXI : 266.500 MHz
- PER : 24 MHz
- DDR : 533 MHz
WDT:   Started with servicing (32s timeout)
NAND:  512 MiB
MMC:   STM32 SD/MMC: 1
In:    serial
Out:   serial
Err:   serial
Model: Digi International ConnectCore MP15 Development Kit
ConnectCore MP15 SOM variant 0x01: 512 MiB DDR3, Wi-Fi, Bluetooth
  Board version 1
Boot:  NAND
Net:   eth0: ethernet@5800a000
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/ccmp15-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:
   -a <atf-filename>      Arm-trusted-firmware filename.
                          Auto-determined by variant if not provided.
   -f <fip-filename>      FIP filename.
                          Auto-determined by variant if not provided.
   -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-webkit' if not provided.
   -n                     No wait. Skips 10 seconds delay to stop script.
   -d                     Install firmware on dualboot partitions (system A and system B).

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

    $ ./install_linux_fw_uuu.sh

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