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:
Download the latest Universal Update Utility (UUU) tool, a software tool from NXP.
Place the uuu executable in a directory in your PATH, such as
udevrules to allow any user to run the uuu for accessing the USB port:
~$ sudo sh -c "uuu -udev >> /etc/udev/rules.d/99-uuu.rules" ~$ sudo udevadm control --reload-rules
Connect a micro USB cable to your development PC and the other end to the target USB OTG connector.
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 dub-2020.04-r2.2 (Jan 18 2021 - 15:58:10 +0000) CPU: i.MX6UL rev1.2 528 MHz (running at 396 MHz) CPU: Industrial temperature grade (-40C to 105C) at 32C Reset cause: POR I2C: ready DRAM: 256 MiB MCA: HW_VER=1 FW_VER=1.19 PMIC: PFUZE3000 DEV_ID=0x30 REV_ID=0x11 NAND: 256 MiB MMC: FSL_SDHC: 0 In: serial Out: serial Err: serial Model: Digi International ConnectCore 6UL SBC. ConnectCore 6UL SOM variant 0x06: Industrial Ultralite 528MHz, 256MB NAND, 256MB DDR3, -40/+85C, Wireless, Bluetooth Board version 3, ID 135 Boot device: NAND Net: FEC0 [PRIME] Fastboot: Normal Normal Boot Hit any key to stop autoboot: 0 =>
Information in the console log may vary.
On the target, in U-Boot, execute the following command:
=> fastboot 0
On your development PC, change to your Digi Embedded Yocto project’s deploy images folder and execute the following command:
~$ cd tmp/deploy/images/ccimx6ulsbc/ ~$ ./install_linux_fw_uuu.sh
Once the firmware is installed, the device boots automatically. The default username is root with no password.