Building & Programming

Note: This is if you want to use Circuit Dojo's Zephyr Tools extension.

Building

In VSCode you can build a project with the

Zephyr Tools: Build

Zephyr Tools: Build Pristine

commands.

You can also build manually by running this in your application root:

west build -b circuitdojo_feather_nrf9151/nrf9151/ns -p -d build/circuitdojo_feather_nrf9151 --sysbuild

Note: the board target name has changed in NCS 2.7 for usage with west it's now: circuitdojo_feather_nrf9151/nrf9151/ns

While not required, it's recommended to have the rust toolchain installed before you install probe-rs. Install rustup first by following the instructions here. This is useful for installing probe-rs and other Rust tools from source.

To install use:

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/probe-rs/probe-rs/releases/latest/download/probe-rs-tools-installer.sh | sh

You will also need to set up udev rules on Linux. See here for more info.

For the nRF9160, you can program using:

probe-rs download --chip nRF9160_xxAA --binary-format hex path/to/merged.hex

For the nRF9151, you can program using:

probe-rs download --chip nRF9151_xxAA --binary-format hex path/to/merged.hex

And once the probe-rs runner has made its way to NCS:

west flash --runner probe-rs

More info on probe-rs can be found on their website.

Securing the Bootloader

By default, MCUboot uses a built-in signing key that is not secure. You'll see this warning during build:

WARNING: Using default MCUboot signing key file, this file is for debug use only and is not secure!

To deliver secure over-the-air updates, you need to generate your own signing key. Here's the process:

Generate an ECDSA-P256 key using imgtool:

pip install imgtool
imgtool keygen -k your-signing-key.pem -t ecdsa-p256

Place the .pem file in your application root directory (next to prj.conf).

In your sysbuild.conf, point to the key file:

SB_CONFIG_BOOTLOADER_MCUBOOT=y
SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="${APPLICATION_CONFIG_DIR}/your-signing-key.pem"

Then start a pristine build using west:
```
west build -b circuitdojo_feather_nrf9151/nrf9151/ns -p --sysbuild
```
Make sure you're building with --sysbuild or have it enabled in the VSCode extension (on by default).

A pristine build should happen before releasing so the version data is up to date. For newer versions of the SDK, the update artifact is located at build/dfu_application.zip instead of app_update.bin. It's critical not to lose your-signing-key.pem as it's the key for (secure) OTA updates to succeed.