Compiler warning question

cptel

<…. a bit long …>
NOTE: I do not use UART and would like to disable it for power savings for final production build. My application works as expected with the exception of power savings due to UART not disabled.

My build file is set as follows:

I am using the default settings in ‘circuitdojo_feather_nrf9151_ns_defconfig’

# Enable uart driver
CONFIG_SERIAL=y

# Enable console
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

and disable them in prj.conf file for my production build:

# Disable console
CONFIG_CONSOLE=n
CONFIG_UART_CONSOLE=n
CONFIG_LOG=n
CONFIG_LOG_MODE_IMMEDIATE=n 
CONFIG_AT_HOST_LIBRARY=n

I am getting these two warnings when I build the project:

-- Including generated dts.cmake file: /opt/pwl/build/mcuboot/zephyr/dts.cmake

warning: UART_CONSOLE (defined at drivers/console/Kconfig:42) was assigned the value 'y' but got the
value 'n'. Check these unsatisfied dependencies: CONSOLE (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_UART_CONSOLE and/or look up UART_CONSOLE in
the menuconfig/guiconfig interface. The Application Development Primer, Setting Configuration
Values, and Kconfig - Tips and Best Practices sections of the manual might be helpful too.


warning: I2C (defined at drivers/i2c/Kconfig:9) was assigned the value 'n' but got the value 'y'.
See http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_I2C and/or look up I2C in the
menuconfig/guiconfig interface. The Application Development Primer, Setting Configuration Values,
and Kconfig - Tips and Best Practices sections of the manual might be helpful too.

Parsing /opt/nordic/ncs/v3.1.1/bootloader/mcuboot/boot/zephyr/Kconfig
Loaded configuration '/opt/nordic/nfed/boards/circuitdojo/feather_nrf9151/circuitdojo_feather_nrf9151_defconfig'
Merged configuration '/opt/nordic/ncs/v3.1.1/bootloader/mcuboot/boot/zephyr/prj.conf'
Merged configuration '/opt/pwl/sysbuild/mcuboot.conf'
Merged configuration '/opt/nordic/ncs/v3.1.1/nrf/modules/mcuboot/tfm.conf'
Merged configuration '/opt/pwl/build/mcuboot/zephyr/.config.sysbuild'
Configuration saved to '/opt/pwl/build/mcuboot/zephyr/.config'
Kconfig header saved to '/opt/pwl/build/mcuboot/zephyr/include/generated/zephyr/autoconf.h'
-- Found GnuLd: /opt/nordic/ncs/toolchains/561dce9adf/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi/bin/ld.bfd (found version "2.38") 
-- The C compiler identification is GNU 12.2.0
-- The CXX compiler identification is GNU 12.2.0
-- The ASM compiler identification is GNU
-- Found assembler: /opt/nordic/ncs/toolchains/561dce9adf/opt/zephyr-sdk/arm-zephyr-eabi/bin/arm-zephyr-eabi-gcc
-- Using ccache: /opt/nordic/ncs/toolchains/561dce9adf/bin/ccache
CMake Warning at /opt/nordic/ncs/v3.1.1/zephyr/CMakeLists.txt:1002 (message):
  No SOURCES given to Zephyr library:
  ..__..__..__nfed__boards__circuitdojo__feather_nrf9151

  Excluding target from build.


MCUBoot bootloader key file: /opt/nordic/ncs/v3.1.1/bootloader/mcuboot/root-ec-p256.pem
CMake Warning at CMakeLists.txt:393 (message):
  WARNING: Using default MCUboot signing key file, this file is for debug use
  only and is not secure!`

It appears that the build process is picking up circuitdojo_feather_nrf_9151_defconfig instead of circuitdojo_feather_nrf_9151_ns_defconfig

what am I doing wrong?

jaredwolff

https://github.com/circuitdojo/nrf9160-feather-examples-and-drivers/blob/v3.1.x/samples/active_sleep/src/main.c

You may want to check this out. I disable it at runtime so I can use it for debugging during development.

Some of the other images may initialize the UART so it’s best to de-init purposefully in your application .

AchimKraus

CONFIG_SERIAL=y

Do you use that still enabled? Try to switch it off with n.

cptel

Thank you Jared & Achim!
setting CONFIG_SERIAL=n didn’t make a difference.

related question…. why does the build process select: circuitdojo_feather_nrf9151_defconfig file and not circuitdojo_feather_nrf9151nsdefconfig file when Board target is set for ’circuitdojo_feather_nrf9151/nrf9151/ns ?

jaredwolff

Depends on which image it’s building. The non NS is for MCUboot and TFM. NS is typically for application code.

cptel

fyi… added the following code and noting about 600mA current drop - thanks!

            static const struct device *const console_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
            /* Disable console UART */
            int err = pm_device_action_run(console_dev, PM_DEVICE_ACTION_SUSPEND);
            if (err < 0)
            {
                LOG_ERR("Unable to suspend console UART. (err: %d)", err);
            }

jaredwolff

Perfect!

AchimKraus

setting CONFIG_SERIAL=n didn’t make a difference.

In my experience, that’s the “game-changer”, equal to suspend the console device.
If you change the “prj.conf”, it sometimes requires a “–pristine” build, otherwise the changes may be not considered.

cptel

one more warning question, the two warnings in YELLOW, do I need to worry about it?

by now… if you haven’t guessed, I am not a build/compiler master 🙂

going through the process of dotting the i’s and crossing the t’s before making that production build

jaredwolff

cptel the main warning that you should care about is the default MCUboot signing key. You should generate your own to secure your application.

https://docs.circuitdojo.com/nrf9160-feather/programming-and-debugging.html?highlight=Mcuboot#securing-the-bootloader

cptel

I followed the steps listed on your site:

Created the cptel-key-rs-2048.pem certificate (success)

Created mcuboot.conf file and added it to my ./src/ directory. Here’s a copy of it:

CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
CONFIG_BOOT_SIGNATURE_KEY_FILE="cptel-key-rsa-2048.pem"

Moved the .pem certificate to same folder as mcuboot.conf

Updated my CMakeLists.txt to include the MCU boot overlay file:

# SPDX-License-Identifier: Apache-2.0

cmake_minimum_required(VERSION 3.11)

# MCUboot related
list(APPEND MCUBOOT_OVERLAY_CONFIG
  "${CMAKE_CURRENT_SOURCE_DIR}/src/mcuboot.conf"
  )


find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
project(pwl)

target_sources(app PRIVATE src/main.c)

Build with PRISTINE option, as I always do. I get images but still see the warning and do not see any reference to the cptel-key-rsa-2048.pem file as part of the build log:

jaredwolff

Ahh those are out of date. I’ll have to update them.

In your application root, add a sysbuild.conf (you should have one if you enabled the bootloader anyway) Add an additional line to point towards your key file.

SB_CONFIG_BOOTLOADER_MCUBOOT=y
SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="\${APPLICATION_CONFIG_DIR}/cptel-key-rsa-2048.pem.pem"

Make sure when you’re building you are using --sysbuild or enable it in the VSCode extension (on by default)

cptel

this helped tremendously.

one additional thing, the 2048-byte RSA generated key (per your instructions) did not work as the MCUboot expects ecdsa_pub_key. I generated an ECDSA-P256 key using same imgtool.py and it compiled fine.

next step - testing 🙂

jaredwolff

Excellent! Added a section on the docs about this:

https://docs.circuitdojo.com/nrf9151-feather/building-and-programming.html#securing-the-bootloader