Use of EXTRA_ZEPHYR_MODULES and custom board within a project with several freestanding apps

[Ignacio]

Some guidance on this query,please.
I have a project with several freestanding application (please check topology below). I would like all the apps to acccess a custom board definition. I use the same zephyr west workspace for several projects so I would not like to follow the example-application T2: Star topology.

For that purpose I have added a zephyr/moudles.yml with the following parameters:

# Copyright (c) 2021 Nordic Semiconductor ASA
# SPDX-License-Identifier: Apache-2.0

build:
settings:
# Additional roots for boards and DTS files. Zephyr will use the
# `<board_root>/boards` for additional boards. The `.` is the root of this
# repository.
board_root: .

and also added below line to CMakeList.txt file of each app:

set(EXTRA_ZEPHYR_MODULES ../)

File Structure

<opt/zephyr>/
└──── zephyrproject/
├─── .west/
│ └─── config
├── zephyr/
├── bootloader/
├── modules/
└── ...


<home/user>/
└─── project/
|───app1/
| ├── CMakeLists.txt
| ├── prj.conf
| └── src/
| └── main.c
|───app2/
| ├── CMakeLists.txt
| ├── prj.conf
| └── src/
| └── main.c
|───app3/
| ├── CMakeLists.txt
| ├── prj.conf
| └── src/
| └── main.c
|
|───boards/arm/custom_board
| └── ...
|
└── zephyr/
└── module.yml

Am I missing sth? Is this structure possible at all?

Thanks

[Vidar Berg]

Hello,

I beleive you need to specify the absolute path to your zephyr module when setting it from your CMakelists.txt file before find_package().

e.g.,

cmake_minimum_required(VERSION ...
set(EXTRA_ZEPHYR_MODULES "${CMAKE_CURRENT_SOURCE_DIR}/../")

find_package(..

 

Also, 'boards' should be a subdirectory of your module directory. 

e.g.,

my_module/
├── boards
│   └── arm
└── zephyr
└── module.yml

module.yml

build:
  settings:
    board_root: .

Another way to use an out-of-tree board without creating a new Zephyr module is to append the path to your board root to the BOARD_ROOT variable by adding the following line to your CMakeLists.txt file: 

list(APPEND BOARD_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../)

Regardless of the approach you use, you may need to specify the board root path in the VS code extension for it to detect your custom board:

https://docs.nordicsemi.com/bundle/nrf-connect-vscode/page/guides/bd_boards_devices.html#finding-new-boards 

Best regards,

Vidar

[Ignacio]

Thanks for the prompt reply Vidar. If I try to set the module directly on the proect folder, I get the below error. Is there a way to overcome this? Is it a requirement to place the modules files on a separate directory?

CMake Error at /opt/ncs/v2.6.0/zephyr/CMakeLists.txt:591 (add_subdirectory):
The binary directory

/home/x/git/zephyr_project_sample/source/build

is already used to build a source directory. It cannot be used to build
source directory

/home/x/git/zephyr_project_sample

Specify a unique binary directory name.

[Vidar Berg]

Hi,

I tried testing this on my end but did not encounter any build errors. I've attached the test sample I created. Could you please review it to see what we are doing differently?

external_module_test.zip

Folder structure:

external_module_test/
├── hello_world
│   ├── build
│   ├── CMakeLists.txt
│   ├── prj.conf
│   ├── README.rst
│   ├── sample.yaml
│   └── src
├── hello_world_1
│   ├── build
│   ├── CMakeLists.txt
│   ├── prj.conf
│   ├── README.rst
│   ├── sample.yaml
│   └── src
└── my_module
├── boards
└── zephyr