The ConnectCore 6UL platform uses U-Boot (Universal Bootloader) as its primary bootloader. U-Boot is an open-source project. You can find standard documentation about commands, environment variables, Flattened Device Tree support, and more at www.denx.de/wiki/U-Boot/Documentation.

About this guide

This guide only describes specific changes made to the standard U-Boot by Digi International.

Version

U-Boot for ConnectCore 6UL is based on standard U-Boot v2020.04 plus NXP patches at https://source.codeaurora.org/external/imx/uboot-imx/.

Supported interfaces

The U-Boot for ConnectCore 6UL supports the following interfaces:

  • UART5 for console (115200/8/N/1)

  • DDR3

  • NAND Flash

  • uSD card (on USDHC2)

  • 10/100Mbps Ethernet on SMSC LAN8720 PHY (RMII)

  • I2C multi-port

  • One-Time-Programmable (OTP) bits

U-Boot has not fully implemented device tree support. Although U-Boot source code contains a device tree, not all drivers make use of this information. Changes you make to the U-Boot device tree may not have any effect if the modified nodes and properties are not supported by their corresponding drivers.

Fastboot support

Fastboot protocol is a mechanism for communicating with bootloaders over USB. It is designed to be used across a wide range of devices and from hosts running different operating systems.

Fastboot enables you to boot and control your device, including:

  • Running any U-Boot command on the target from your host machine

  • Downloading images and files directly into RAM

  • Programming and erasing entire partitions from NAND

To start Fastboot on your device, run the fastboot command:

=> fastboot <USB interface>

This leaves the device awaiting communication from the host through the selected USB interface. You can use UUU NXP tool in your host machine to communicate with the device.

See the UUU release repository for additional Fastboot documentation.

Carrier board version and ID

Digi uses non-volatile media to store the carrier board version and ID. See Carrier board version and ID.