The ConnectCore 8X 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

About this guide

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


U-Boot for ConnectCore 8X is based on standard U-Boot v2018.03 plus NXP patches at

Supported interfaces

The U-Boot for ConnectCore 8X supports the following interfaces:

  • LPUART2 for console (115200/8/N/1)

  • LPDDR4

  • eMMC for storage (on USDHC1)

  • uSD card (on USDHC2)

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

  • 10/100/1000Mbps Ethernet on Atheros AR8031 PHY (RGMII) on SBC Pro

  • I2C multi-port

  • One-Time-Programmable (OTP) bits

  • USB device for Fastboot communication

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 eMMC

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.