The ConnectCore MP15 platform uses ARM Trusted Firmware-A (TF-A) as first stage bootloader and U-Boot (Universal Bootloader) as second stage 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 MP15 is based on standard U-Boot v2021.10 plus STMicroelectronics patches at

Supported interfaces

The U-Boot for ConnectCore MP15 supports the following interfaces:

  • UART4 for console (115200/8/N/1)

  • DDR3L

  • NAND

  • microSD card

  • 10/100/1000Mbps Ethernet on Marvell 88E1512 PHY (RGMII)

  • 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 NAND

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

=> fastboot 0

This leaves the device awaiting communication from the host through the selected USB interface. You can use NXP Universal Update Utility (uuu) in your host machine to communicate with the device.

See the uuu repository for additional information.

Carrier board version and ID

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