Chapter 5
Building and programming with MCUXpresso
5.1 Understanding the boot flow
shows the series of checks that occur during the boot. There are configuration options in various applications (ROM
bootloader, bootstrap, bootloader) that determine which sequence is followed. If at any point a signature check fails and the High
Assurance Booting (HAB) or image verification is enabled, the boot process stops.
Figure 15. Boot security flowchart
By default, the SLN-LOCAL2-IOT kit has the image verification enabled and the HAB disabled in the bootstrap and bootloader.
The bootstrap project is the first application that boots. The architecture is described below. Bootstrap is a minimal FreeRTOS
application that is responsible for image verification. If the i.MX RT HAB is enabled on the chip, bootstrap is the signed trusted
firmware. This firmware is designed to avoid any updates, because the corruption of this image results in unbootable image and
bricked device.
The bootloader project is a second-stage bootloader that manages jumping into the local_demo application. This application can
be used for any additional bootloader functionality needed for the product. This bootloader is also responsible for the Mass Storage
Device (MSD) dragging and dropping and updating the application image Over-the-Air (OTA) as well as Over-the-Wire (OTW).
The bootloader also validates OTA / OTW images via signature verification.
The local_demo is the main application that runs the far-field local voice control.
5.2 Building the bootstrap, bootloader, and local voice control demo
From the "Quickstart Panel", select “Build” to start the compilation and linking of the application for sln_local2_iot_bootstrap,
sln_local2_iot_bootloader, and sln_local2_iot_local_demo.
shows that the sln_local2_iot_local_demo project is selected
and will start to compile after clicking the “Build” button.
NXP Semiconductors
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