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Merged
gminn merged 1 commit into from
Jan 15, 2026
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update practical-zephyr series to recent versions of Zephyr and the nRF Connect SDK #620

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112 changes: 75 additions & 37 deletions _posts/2024-01-10-practical_zephyr_basics.md
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78 changes: 39 additions & 39 deletions _posts/2024-01-24-practical_zephyr_kconfig.md
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ The simplest way to log text in Zephyr is the `printk` function. `printk` can ta
#include <zephyr/kernel.h>
#define SLEEP_TIME_MS 100U

void main(void)
int main(void)
{
printk("Message in a bottle.\n");
while (1)
Expand All @@ -67,7 +67,7 @@ As mentioned in the previous article, we're using a development kit from [Nordic
The connection settings for the UART interface are configured using [devicetree](https://docs.zephyrproject.org/latest/build/dts/index.html) - which we'll explore in a later article. Since these default settings are all we need for now, let's focus on Kconfig. We build and flash the project as follows:

```bash
$ west build --board nrf52840dk_nrf52840 --build-dir ../build
$ west build --no-sysbuild --board nrf52840dk/nrf52840 --build-dir ../build
$ west flash --build-dir ../build
```

Expand Down Expand Up @@ -157,7 +157,7 @@ In the header file `zephyr/lib/os/printk.h` we can see that `printk` is replaced
With `printk` disabled in our application configuration file, let's try to rerun our application to verify that the output is indeed disabled:

```bash
$ west build --board nrf52840dk_nrf52840 --build-dir ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 --build-dir ../build --pristine
$ west flash --build-dir ../build
```

Expand Down Expand Up @@ -202,7 +202,7 @@ Zephyr contains _hundreds_ of so-called Kconfig _fragments_. It is therefore alm
For the `build` command, _West_ has some builtin _targets_, two of which are used for _Kconfig_:

```bash
$ west build --build-dir ../build -t usage
$ west build --no-sysbuild --build-dir ../build -t usage
-- west build: running target usage
...
Kconfig targets:
Expand Down Expand Up @@ -276,7 +276,7 @@ The downside of saving the configuration to `zephyr/.config` in the build direct
The people at [Golioth](https://golioth.io/) published a [short article](https://blog.golioth.io/zephyr-quick-tip-show-what-menuconfig-changed-and-make-changes-persistent/) that shows how to leverage the `diff` command to find out which configuration options have changed when using the normal _Save_ operation: Before writing the changes to the `zephyr/.config` file, Kconfig stores the old configuration in `build/zephyr/.config.old`. Thus, all changes that you make between a _Save_ operation are reflected by the differences between `zephyr/.config` and `build/zephyr/.config.old`:

```bash
$ west build --board nrf52840dk_nrf52840 -d ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build --pristine
$ west build -d ../build -t menuconfig
# Within menuconfig:
# - Disable BOOT_BANNER and PRINTK.
Expand Down Expand Up @@ -306,7 +306,7 @@ Both `menuconfig` and `guiconfig` have the _Save minimal config_ option. As the
Let's try this out with our settings for the `BOOT_BANNER` and `PRINTK` symbols.

```bash
$ west build --board nrf52840dk_nrf52840 -d ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build --pristine
$ west build -d ../build -t menuconfig
# Within menuconfig:
# - Disable BOOT_BANNER and PRINTK.
Expand All @@ -331,7 +331,7 @@ CONFIG_UART_CONSOLE=y
CONFIG_EARLY_CONSOLE=y
```

As you can see, this minimal configuration contains a lot more options than we changed within `menuconfig`. Some of these options come from the selected board, in my case `zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig`, but are still listed since they do not use default values. However, the two changes to `PRINTK` and `BOOT_BANNER` are still visible. We can just take those options and write them to our application configuration file:
As you can see, this minimal configuration contains a lot more options than we changed within `menuconfig`. Some of these options come from the selected board, in my case `zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig`, but are still listed since they do not use default values. However, the two changes to `PRINTK` and `BOOT_BANNER` are still visible. We can just take those options and write them to our application configuration file:

```bash
$ cat prj.conf
Expand Down Expand Up @@ -359,9 +359,9 @@ At the time of writing and for this repository, the following configuration opti

```json
{
"nrf-connect.toolchain.path": "${nrf-connect.toolchain:2.4.0}",
"nrf-connect.topdir": "${nrf-connect.sdk:2.4.0}",
"kconfig.zephyr.base": "${nrf-connect.sdk:2.4.0}",
"nrf-connect.toolchain.path": "${nrf-connect.toolchain:3.2.1}",
"nrf-connect.topdir": "${nrf-connect.sdk:3.2.1}",
"kconfig.zephyr.base": "${nrf-connect.sdk:3.2.1}",
"nrf-connect.applications": ["${workspaceFolder}/path/to/app"]
}
```
Expand Down Expand Up @@ -425,14 +425,14 @@ We can now instruct _West_ to use this `prj_release.conf` _instead_ of our `prj.

```bash
$ rm -rf ../build
$ west build --board nrf52840dk_nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
```

If you scroll through the output of the `west build` command, you'll notice that _Kconfig_ merged `prj_release.conf` into our final configuration:

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj_release.conf'
Configuration saved to '/path/to/zephyr_practical/build/zephyr/.config'
```
Expand All @@ -447,7 +447,7 @@ Aside from the application configuration file [prj.conf](https://github.com/lmap

E.g., throughout this guide, we're using the nRF52840 development kit, which has the board name `nrf52840dk_nrf52840`. Thus, the file `boards/nrf52840dk_nrf52840.conf` is automatically merged into the `Kconfig` configuration during the build, if present.

Let's try this by disabling UART as console output using a new fragment `boards/nrf52840dk_nrf52840.conf`. For the nRF52840 development kit, this symbol is enabled by default. You can go ahead and verify this by checking the default configuration `zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig` - or take my word for it:
Let's try this by disabling UART as console output using a new fragment `boards/nrf52840dk_nrf52840.conf`. For the nRF52840 development kit, this symbol is enabled by default. You can go ahead and verify this by checking the default configuration `zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig` - or take my word for it:

```bash
tree --charset=utf-8 --dirsfirst
Expand All @@ -470,19 +470,19 @@ CONFIG_UART_CONSOLE=n
Then, we perform a _pristine_ build of the project. Notice that a `--pristine` build is required at this point because otherwise, the build system does not pick up our newly added `.conf` file. This is one of the very few occasions where a pristine build is actually required.

```bash
$ west build --board nrf52840dk_nrf52840 -d ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build --pristine
```

In the output of `west build` shown below you can see that the new file `boards/nrf52840dk_nrf52840.conf` is indeed merged into the `Kconfig` configuration. You can also see a warning that the Zephyr library `drivers__console` is excluded from the build since it now has no `SOURCES`:

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj.conf'
Merged configuration '/path/to/01_kconfig/boards/nrf52840dk_nrf52840.conf'
Configuration saved to '/path/to/build/zephyr/.config'
...
CMake Warning at /opt/nordic/ncs/v2.4.0/zephyr/CMakeLists.txt:838 (message):
CMake Warning at /opt/nordic/ncs/v3.2.1/zephyr/CMakeLists.txt:838 (message):
No SOURCES given to Zephyr library: drivers__console
Excluding target from build.
```
Expand All @@ -495,12 +495,12 @@ How are board fragments used by our previously created `release` build type? Let

```bash
$ rm -rf ../build
$ west build --board nrf52840dk_nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
```

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj_release.conf'
Configuration saved to '/path/to/build/zephyr/.config'
```
Expand Down Expand Up @@ -533,12 +533,12 @@ Now, when we rebuild the project, we see that our board fragment is merged into

```bash
$ rm -rf ../build
$ west build --board nrf52840dk_nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build -- -DCONF_FILE=prj_release.conf
```

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj_release.conf'
Merged configuration '/path/to/01_kconfig/boards/nrf52840dk_nrf52840_release.conf'
Configuration saved to '/path/to/build/zephyr/.config'
Expand Down Expand Up @@ -579,13 +579,13 @@ We can now pass the two extra configuration fragments to the build system using

```bash
$ rm -rf ../build
$ west build --board nrf52840dk_nrf52840 -d ../build -- \
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build -- \
-DEXTRA_CONF_FILE="extra0.conf;extra1.conf"
```

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj.conf'
Merged configuration '/path/to/01_kconfig/boards/nrf52840dk_nrf52840.conf'
Merged configuration '/path/to/01_kconfig/extra0.conf'
Expand All @@ -597,14 +597,14 @@ The fragments specified using the `EXTRA_CONF_FILE` variable are merged into the

```bash
$ rm -rf ../build
$ west build --board nrf52840dk_nrf52840 -d ../build -- \
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build -- \
-DCONF_FILE="prj_release.conf" \
-DEXTRA_CONF_FILE="extra1.conf;extra0.conf"
```

```
Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj_release.conf'
Merged configuration '/path/to/01_kconfig/boards/nrf52840dk_nrf52840_release.conf'
Merged configuration '/path/to/01_kconfig/extra1.conf'
Expand All @@ -620,13 +620,13 @@ We can use this tool to check our normal and _release_ configurations:

```bash
$ # test normal build
$ west build --board nrf52840dk_nrf52840 \
$ west build --no-sysbuild --board nrf52840dk/nrf52840 \
-d ../build \
--pristine \
-t hardenconfig

$ # test release build
$ west build --board nrf52840dk_nrf52840 \
$ west build --no-sysbuild --board nrf52840dk/nrf52840 \
-d ../build \
--pristine \
-t hardenconfig \
Expand All @@ -637,7 +637,7 @@ For the normal build using `prj.conf`, the hardening tool displays a table of al

```
-- west build: running target hardenconfig
[0/1] cd /path/to/zephyr/kconfig/hardenconfig.py /opt/nordic/ncs/v2.4.0/zephyr/Kconfig
[0/1] cd /path/to/zephyr/kconfig/hardenconfig.py /opt/nordic/ncs/v3.2.1/zephyr/Kconfig
name | current | recommended || check result
==============================================================================
CONFIG_OVERRIDE_FRAME_POINTER_DEFAULT | n | y || FAIL
Expand Down Expand Up @@ -707,12 +707,12 @@ By sourcing the `Kconfig.zephr` file, we're loading all _Kconfig_ menus and symb
Let's rebuild our application without configuring `USR_FUN` and have a look at the build output. A `--pristine` build is required to pick up the new `Kconfig` file:

```bash
$ west build --board nrf52840dk_nrf52840 -d ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build --pristine
```

```
Parsing /path/to/01_kconfig/Kconfig
Loaded configuration '/opt/nordic/ncs/v2.4.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Loaded configuration '/opt/nordic/ncs/v3.2.1/zephyr/boards/nordic/nrf52840dk/nrf52840dk_nrf52840_defconfig'
Merged configuration '/path/to/01_kconfig/prj.conf'
Merged configuration '/path/to/01_kconfig/boards/nrf52840dk_nrf52840.conf'
Configuration saved to '/path/to/build/zephyr/.config'
Expand All @@ -721,7 +721,7 @@ Kconfig

Have a good look at the very first line of the _Kconfig_-related output:
* In our previous builds, this line indicated the use of Zephyr's default `Kconfig` file as follows:
`Parsing /opt/nordic/ncs/v2.4.0/zephyr/Kconfig`,
`Parsing /opt/nordic/ncs/v3.2.1/zephyr/Kconfig`,
* Whereas now it uses our newly created `Kconfig` file:
`Parsing /path/to/01_kconfig/Kconfig`.

Expand Down Expand Up @@ -813,7 +813,7 @@ Let's first extend our `main.c` file to use `usr_fun` regardless of any configur

#define SLEEP_TIME_MS 100U

void main(void)
int main(void)
{
printk("Message in a bottle.\n");
usr_fun();
Expand All @@ -828,7 +828,7 @@ void main(void)
Unsurprisingly, building this application fails since `usr_fun.c` is not included in the build:

```bash
$ west build --board nrf52840dk_nrf52840 -d ../build --pristine
$ west build --no-sysbuild --board nrf52840dk/nrf52840 -d ../build --pristine
```

```
Expand Down Expand Up @@ -860,7 +860,7 @@ This, however, defeats the purpose of having a configurable build: The build wou

#define SLEEP_TIME_MS 100U

void main(void)
int main(void)
{
printk("Message in a bottle.\n");

Expand Down
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