Undefined driver enable symbols when adding local driver and Kconfig

Supporting observation that newly created Kconfig causes the above multiple undefined symbols errors, when I set aside the Kconfig in project directory blink-plus-uart the error count goes to one. Only the symbol I referenced for the new sensor driver is undefined. Truthfully I do not yet know where to define this symbol, and I could locate through recursive pattern matching where any of the other undefined symbols above are defined in ncs 1.6.1 or the Zephyr release tag within ncs 1.6.1.

Build messages here for same project as throughout this post, but Kconfig along side src/main.c and the newly added drivers directory and subdirs moved aside and not visible to cmake:

ted@localhost:~/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart$ west build -b sparkfun_thing_plus_nrf9160 -p
-- west build: making build dir /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/build pristine
-- west build: generating a build system
Including boilerplate (Zephyr base): /home/ted/projects/embedded/ncs/zephyr/cmake/app/boilerplate.cmake
-- Application: /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart
-- Zephyr version: 2.6.0-rc1 (/home/ted/projects/embedded/ncs/zephyr), build: v2.6.0-rc1-ncs1
-- Found Python3: /usr/bin/python3.8 (found suitable exact version "3.8.10") found components: Interpreter 
-- Found west (found suitable version "0.11.0", minimum required is "0.7.1")
-- Board: sparkfun_thing_plus_nrf9160
-- Cache files will be written to: /home/ted/.cache/zephyr
-- Using toolchain: zephyr 0.12.4 (/opt/zephyr-sdk-0.12.4)
-- Found dtc: /opt/zephyr-sdk-0.12.4/sysroots/x86_64-pokysdk-linux/usr/bin/dtc (found suitable version "1.5.0", minimum required is "1.4.6")
-- Found BOARD.dts: /home/ted/projects/embedded/ncs/zephyr/boards/arm/sparkfun_thing_plus_nrf9160/sparkfun_thing_plus_nrf9160.dts
-- Found devicetree overlay: /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/app.overlay
sparkfun_thing_plus_nrf9160.dts.pre.tmp:59.42-71.3: Warning (unique_unit_address_if_enabled): /soc/peripheral@50000000/flash-controller@39000: duplicate unit-address (also used in node /soc/peripheral@50000000/kmu@39000)
sparkfun_thing_plus_nrf9160.dts.pre.tmp:311.19-317.3: Warning (unique_unit_address_if_enabled): /soc/peripheral@50000000/clock@5000: duplicate unit-address (also used in node /soc/peripheral@50000000/power@5000)
-- Generated zephyr.dts: /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/build/zephyr/zephyr.dts
-- Generated devicetree_unfixed.h: /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/build/zephyr/include/generated/devicetree_unfixed.h
-- Generated device_extern.h: /home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/build/zephyr/include/generated/device_extern.h
Parsing /home/ted/projects/embedded/ncs/zephyr/Kconfig
Loaded configuration '/home/ted/projects/embedded/ncs/zephyr/boards/arm/sparkfun_thing_plus_nrf9160/sparkfun_thing_plus_nrf9160_defconfig'
Merged configuration '/home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/prj.conf'

/home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/prj.conf:7: warning: attempt to assign the value 'y' to the undefined symbol KX132_1211

error: Aborting due to Kconfig warnings

CMake Error at /home/ted/projects/embedded/ncs/zephyr/cmake/kconfig.cmake:264 (message):
  command failed with return code: 1
Call Stack (most recent call first):
  /home/ted/projects/embedded/ncs/zephyr/cmake/app/boilerplate.cmake:555 (include)
  /home/ted/projects/embedded/ncs/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:24 (include)
  /home/ted/projects/embedded/ncs/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:35 (include_boilerplate)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
FATAL ERROR: command exited with status 1: /usr/bin/cmake -DWEST_PYTHON=/usr/bin/python3 -B/home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart/build -S/home/ted/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart -GNinja -DBOARD=sparkfun_thing_plus_nrf9160
ted@localhost:~/projects/embedded/ncs/zephyr/samples/sandbox-de-ted/blink-plus-uart$

Hi Jared. This may be a very basic question: where is, or how do I determine, the outside-of-app file to change so drivers needed by the app are built first?

At this point now I’ve spent a good ten plus hours searching, reading, and experimenting with various suggested example changes to correctly “inform” my project of the larger Nordic SDK in which it lives. This has only become an issue as I implement a local driver.

I’ve reviewed each of your replies, again much appreciated, and I’ve looked pretty extensively over the pyrinas project you have on github. When I add a Kconfig.kx132 in the top dir of my example app, a file analogous to Kconfig.pyrinas, this causes all of the blinky driver enable flags to become undefined. Without this app top-level Kconfig file, only my newly drafted driver flag CONFIG_KX132_1211 is not found by cmake and reported as undefined.

Where exactly should a variable such as CONFIG_PCF85063A be defined? I find many references to Zephyr’s official driver CONFIG_ flags, but no place in the Zephyr 2.6.0 cloned repository, nor the ncs 1.6.1 repository where any of these flags are pound defined.

As for knowing the context of my example app, I know that I am using for my SDK, ncs v1.6.1. I know which directory is the root dir of this SDK where I ran west init. I know the path from this SDK root to the basic\blinky example, and likewise to my modified version of that example app. But if to “include my driver outside my app” requires a “within app” change, it is unclear to me which file and which stanzas to change.

You state I “must include my drivers outside of my application”. How does one include one’s drivers outside of their application? Must modify a file outside my app in the larger SDK, or a file within my app?

Looking at the original Nordic ncs 1.6.1 / Zephyr basic/blinky app, I see there is a CMakeLists.txt file but no Kconfig file. The CMakeLists.txt file contains:

 # SPDX-License-Identifier: Apache-2.0
  2
  3 cmake_minimum_required(VERSION 3.13.1)
  4 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
  5 project(blinky)
  6
  7 target_sources(app PRIVATE src/main.c)

If I follow your blog post tutorial verbatim, I would overwrite this file with something like the following pyrinas, app-top-level-directory CMakeLists.txt file:

#
# Copyright (c) 2020 Circuit Dojo
#
# SPDX-License-Identifier: Apache-2.0
#

# Point to Pyrinas root directory.
set(PYRINAS_DIR ${CMAKE_CURRENT_LIST_DIR} CACHE PATH "Pyrinas root directory")

zephyr_include_directories(include)

add_subdirectory(lib)
add_subdirectory(ext)
add_subdirectory(drivers)

In adding this file to my project I would substitute my project name for ‘pyrinas’, but I’m concerned to delete the find_package() and target_sources() stanzas that are present in my pre-existing CMakeLists.txt file. This file pre-exists because my app is copied from basic/blinky. At this time I also do not have an ext nor lib subdirectly in my example app project.

I’m willing to put in the hours to learn this new material, but as I’m building on an existing example and not from scratch, I need to know which parts of the example are ok to overwrite versus those which must stay in place. This so if I am to follow the blog instructions as close as possible and make them work.

Good evening Jared,
Only last night Satuday 8-21 did I notice your edits to your most recent messages to this longer post. Thank you for the directory structures, reiterated points of import and further guidance. I’m working through these highlighted app and driver pieces now. Hopefully will have a driver which compiles soon!
I may come back to a point I see in the AQW driver top level CMakeLists.txt file. It is not clear to me how to choose what is line 6 in air quality wing CMakeLists.txt:

#
# Copyright (c) 2021 Circuit Dojo LLC
#

# Point to this project's root directory.
set(AQW_DIR ${CMAKE_CURRENT_LIST_DIR} CACHE PATH "Air Quality Wing root directory")

# Subdirectories
add_subdirectory(drivers)
add_subdirectory_ifdef(CONFIG_AQW lib)

# Include headers
zephyr_include_directories(include)
zephyr_include_directories(drivers)

Variable AQW_DIR looks custom, like a name chosen entirely by the developer. I’m searching for where else this is referenced. Is there a naming convention here for this variable? In general terms is this “the given driver root directory”?