Flash overflow in nrf5340-nrf7002

[Lavanya_Manohar]

I'm currently working on implementing OpenThread on our custom board based on the nRF5340 along with the nRF7002. While building the project, I'm encountering the following build error:
  "section `rodata' will not fit in region 'FLASH'"
  "region `FLASH' overflowed"
This seems to indicate that the application is exceeding the internal flash limits. I’ve already tried disabling optional OpenThread features, but I still see a large `.rodata` footprint.
Could you please advise on best practices to reduce OpenThread’s memory usage in this configuration, especially while retaining support for the peripheral role?

Additionally, is there an officially supported way to move some of the OpenThread data or code into external flash on the nRF5340? If so, a reference or example would be greatly appreciated.

ERROR LOG
c:/ncs/toolchains/cf2149caf2/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: zephyr\zephyr_pre0.elf section `rodata' will not fit in region `FLASH'
c:/ncs/toolchains/cf2149caf2/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: region `FLASH' overflowed by 167144 bytes

Memory region         Used Size  Region Size  %age Used
           FLASH:      784948 B     892416 B     87.96%
             RAM:      403260 B       440 KB     89.50%
        IDT_LIST:          0 GB        32 KB      0.00%

[runsiv]

Hi

Which version of NCS are you using? 

You can have a look here regarding how to optimize the wifi stack https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/wifi/stack_configuration.html#nrf-wi-fi-driver-performance-and-memory-fine-tuning-controls 

Regards

Runar

[Lavanya_Manohar]

We using v2.6.2 

[runsiv]

Is there a specific reason why you are using 2.6.2? In general I would highly recommend using a newer SDK. For example in NCS 3.0 there s up to 25 kB reduction in the RAM footprint of the Wi-Fi stack on nRF5340 for Wi-Fi applications with low throughput requirements. If you need to use 2.6.x for a spesific reason I would at least recommend that you use 2.6.4 as it contain wifi fixes 

What starting point did you use for your application? Due to the changes that was introduced in NCS 2.7 it will contain breaking changes due to the introduction of Sysbuild and HW model 2. These changes can be found in the migration documentation 

[Lavanya_Manohar]

When we started development, NCS v2.6.2 was the latest available version, and our application was built and finalized using this version. The project is now in the production stage, so upgrading the SDK at this point could introduce delays due to the need for regression testing and validation. That’s why we are currently staying on v2.6.2.

However, for future development or if we plan to update the project, we will evaluate compatibility with the latest SDK version. We understand that changes introduced in NCS, so we’ll make sure to review the migration documentation and check for any required updates to APIs or configuration settings.

As we prepare for potential migration, we would like to clarify the following:

1. What are the recommended steps for upgrading an existing application from NCS 2.6.2 to the latest version (e.g., NCS 3.x)?

   • Are there structured guidelines or tools to help transition to newer features like Sysbuild and HW model 2?

   • What should we watch out for in terms of API/configuration updates, board definitions, or system changes?

In the current version (NCS 2.6.2), are there any known methods or best practices to reduce flash usage?

• We are looking to optimize flash consumption

[Marte Myrvold]

Hi,

Lavanya_Manohar said:

What are the recommended steps for upgrading an existing application from NCS 2.6.2 to the latest version (e.g., NCS 3.x)?

We have migration guides in our documentation. There are guides for migrating from one version to the next, so I recommend going through each. In addition, there are specific guides for migrating from multi-image builds to sysbuild and migrating to the current hardware model. Sysbuild and hw model v2 were introduced in v2.7.0, so these guides are relevant when migrating from v2.6 to v2.7.

Lavanya_Manohar said:

In the current version (NCS 2.6.2), are there any known methods or best practices to reduce flash usage?

We have a memory footprint optimization guide that provides general and protocol-specific tips for optimizing and reducing flash and RAM usage.

Best regards,
Marte

[Amirtha]

Hi 

We have installed NCS 3.0 and resolved the build issues. However, we are facing configuration issues related to Wi-Fi and BLE. Our application builds successfully without the Wi-Fi and BLE configurations, but including them causes an issue. Is there any documentation available for updating the Kconfig settings from version 2.6.2 to 3.0?

Best Regards,
Amirtha N

[Marte Myrvold]

Hi Amirtha,

Amirtha said:

Is there any documentation available for updating the Kconfig settings from version 2.6.2 to 3.0?

You can use the migration guides I mentioned in my previous reply.

If you have any specific issues, please share the complete build log as text by using Insert > Code.

Best regards,
Marte

[Amirtha]

Hi team,
   
      Thanks for your reply.

            We have tried to build our code on nRF SDK v3.0.0 and we follow the steps as per mention in migration guide however still we face some compilation issues, here is the complete build log.

Kindly review and provide how to resolve the configuration file warnings

Fullscreen nrf5340_compilation_error.txt Download

warning: COMMON_LIBC_MALLOC_ARENA_SIZE (defined at
C:/ncs/v3.0.0/zephyr/soc/mediatek/mt8xxx/Kconfig.defconfig:76, lib/libc\common/Kconfig:57) was
assigned the value '21144' but got the value ''. Check these unsatisfied dependencies:
(SOC_FAMILY_MTK || COMMON_LIBC_MALLOC) (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE and/or look
up COMMON_LIBC_MALLOC_ARENA_SIZE 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: LOG_BUFFER_SIZE (defined at C:/ncs/v3.0.0/nrf\subsys/net/openthread/Kconfig.defconfig:96,
subsys/logging\Kconfig.processing:122) was assigned the value '1024' but got the value ''. Check
these unsatisfied dependencies: (NET_L2_OPENTHREAD || (LOG_MODE_DEFERRED && !LOG_FRONTEND_ONLY &&
!LOG_MODE_MINIMAL && LOG)) (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_LOG_BUFFER_SIZE and/or look up
LOG_BUFFER_SIZE 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: MBEDTLS_RSA_C (defined at C:/ncs/v3.0.0/nrf\subsys/net/openthread/Kconfig.defconfig:174,
C:/ncs/v3.0.0/nrf\subsys\nrf_security\Kconfig.legacy:736) was assigned the value 'y' but got the
value 'n'. Check these unsatisfied dependencies: (NET_L2_OPENTHREAD || (!MBEDTLS_USE_PSA_CRYPTO &&
MBEDTLS_LEGACY_CRYPTO_C && NRF_SECURITY)) (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_MBEDTLS_RSA_C and/or look up MBEDTLS_RSA_C
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: BT_SETTINGS_CCC_LAZY_LOADING (defined at
C:/ncs/v3.0.0/zephyr/subsys/bluetooth/host/Kconfig:221, subsys/bluetooth\host/Kconfig:221) was
assigned the value 'y' but got the value 'n'. Check these unsatisfied dependencies: ((BT_CONN &&
BT_SETTINGS && BT_HCI_HOST && BT_RPC_STACK) || (BT_CONN && BT_SETTINGS && BT_HCI_HOST && BT_HCI &&
BT)) (=n). See http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_BT_SETTINGS_CCC_LAZY_LOADING
and/or look up BT_SETTINGS_CCC_LAZY_LOADING 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: BT_PERIPHERAL_PREF_TIMEOUT (defined at
C:/ncs/v3.0.0/zephyr/subsys/bluetooth/host\Kconfig.gatt:267, subsys/bluetooth\host\Kconfig.gatt:267)
was assigned the value '75' but got the value ''. Check these unsatisfied dependencies:
((BT_GAP_PERIPHERAL_PREF_PARAMS && BT_CONN && BT_HCI_HOST && BT_RPC_STACK) ||
(BT_GAP_PERIPHERAL_PREF_PARAMS && BT_CONN && BT_HCI_HOST && BT_HCI && BT)) (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_BT_PERIPHERAL_PREF_TIMEOUT and/or look up
BT_PERIPHERAL_PREF_TIMEOUT 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: WIFI_READY_LIB (defined at C:/ncs/v3.0.0/nrf\subsys\net\lib\wifi_ready/Kconfig:7) was
assigned the value 'y' but got the value 'n'. Check these unsatisfied dependencies:
WIFI_NM_WPA_SUPPLICANT (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_WIFI_READY_LIB and/or look up
WIFI_READY_LIB 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: CC3XX_BACKEND (defined at C:/ncs/v3.0.0/nrf\subsys\nrf_security\Kconfig.legacy:335) was
assigned the value 'y' but got the value 'n'. Check these unsatisfied dependencies:
MBEDTLS_LEGACY_CRYPTO_C (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_CC3XX_BACKEND and/or look up CC3XX_BACKEND
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: WDT_DISABLE_AT_BOOT (defined at drivers/watchdog/Kconfig:17) was assigned the value 'y' but
got the value 'n'. Check these unsatisfied dependencies: HAS_WDT_DISABLE_AT_BOOT (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_WDT_DISABLE_AT_BOOT and/or look up
WDT_DISABLE_AT_BOOT 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: NRF_WIFI_RPU_RECOVERY (defined at drivers/wifi/nrf_wifi/Kconfig.nrfwifi:659) was assigned
the value 'y' but got the value 'n'. Check these unsatisfied dependencies: NRF_WIFI_LOW_POWER (=n),
WIFI_NRF70 (=n). See http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_NRF_WIFI_RPU_RECOVERY
and/or look up NRF_WIFI_RPU_RECOVERY 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: PRINTK (defined at subsys/debug/Kconfig:220) was assigned the value 'n' but got the value
'y'. See http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_PRINTK and/or look up PRINTK 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: LOG_PROCESS_THREAD_SLEEP_MS (defined at subsys/logging\Kconfig.processing:72) was assigned
the value '10' but got the value ''. Check these unsatisfied dependencies: LOG_PROCESS_THREAD (=n),
LOG_MODE_DEFERRED (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_LOG_PROCESS_THREAD_SLEEP_MS and/or look up
LOG_PROCESS_THREAD_SLEEP_MS 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: LOG_PROCESS_THREAD_PRIORITY (defined at subsys/logging\Kconfig.processing:112) was assigned
the value '2' but got the value ''. Check these unsatisfied dependencies:
LOG_PROCESS_THREAD_CUSTOM_PRIORITY (=n), LOG_PROCESS_THREAD (=n), LOG_MODE_DEFERRED (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_LOG_PROCESS_THREAD_PRIORITY and/or look up
LOG_PROCESS_THREAD_PRIORITY 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: NET_CONFIG_MY_IPV6_ADDR (defined at subsys/net/lib/config/Kconfig:83) was assigned the
value '2001:db8::1' but got the value ''. Check these unsatisfied dependencies: NET_IPV6 (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_NET_CONFIG_MY_IPV6_ADDR and/or look up
NET_CONFIG_MY_IPV6_ADDR 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: NET_CONFIG_PEER_IPV6_ADDR (defined at subsys/net/lib/config/Kconfig:88) was assigned the
value '2001:db8::2' but got the value ''. Check these unsatisfied dependencies: NET_IPV6 (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_NET_CONFIG_PEER_IPV6_ADDR and/or look up
NET_CONFIG_PEER_IPV6_ADDR 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: NET_DHCPV6 (defined at subsys/net/lib/dhcpv6/Kconfig:12) was assigned the value 'y' but got
the value 'n'. Check these unsatisfied dependencies: NET_IPV6 (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_NET_DHCPV6 and/or look up NET_DHCPV6 in the
menuconfig/guiconfig interface. The Application Development Primer, Setting Configuration Values,
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: Deprecated symbol POSIX_CLOCK is enabled.


warning: Deprecated symbol POSIX_MQUEUE is enabled.


warning: Experimental symbol TFM_EXPERIMENTAL is enabled.


warning: Experimental symbol WIFI_CREDENTIALS is enabled.


warning: Experimental symbol NET_CONNECTION_MANAGER is enabled.


D:/sensors/application/Node_1/prj.conf:45: warning: attempt to assign the value 'y' to the undefined symbol WPA_SUPP

D:/sensors/application/Node_1/prj.conf:142: warning: attempt to assign the value '5' to the undefined symbol WIFI_NRF700X_SCAN_TIMEOUT_S

D:/sensors/application/Node_1/prj.conf:160: warning: attempt to assign the value 'y' to the undefined symbol WIFI_MGMT_EXT

D:/sensors/application/Node_1/prj.conf:271: warning: attempt to assign the value 'n' to the undefined symbol BT_HCI_VS_EXT

D:/sensors/application/Node_1/boards/nrf7002dk_nrf5340_cpuapp.conf:19: warning: attempt to assign the value '16' to the undefined symbol NRF700X_RX_NUM_BUFS

D:/sensors/application/Node_1/boards/nrf7002dk_nrf5340_cpuapp.conf:20: warning: attempt to assign the value '4' to the undefined symbol NRF700X_MAX_TX_AGGREGATION

error: Aborting due to Kconfig warnings

Parsing D:/sensors/application/Node_1/Kconfig
Loaded configuration 'C:/ncs/v3.0.0/zephyr/boards/nordic/nrf7002dk/nrf7002dk_nrf5340_cpuapp_ns_defconfig'
Merged configuration 'D:/sensors/application/Node_1/prj.conf'
Merged configuration 'D:/sensors/application/Node_1/boards/nrf7002dk_nrf5340_cpuapp.conf'
Merged configuration 'D:/sensors/application/Node_1/build/Node_1/zephyr/.config.sysbuild'
CMake Error at C:/ncs/v3.0.0/zephyr/cmake/modules/kconfig.cmake:396 (message):
  command failed with return code: 1
Call Stack (most recent call first):
  C:/ncs/v3.0.0/nrf/cmake/modules/kconfig.cmake:36 (include)
  C:/ncs/v3.0.0/zephyr/cmake/modules/zephyr_default.cmake:133 (include)
  C:/ncs/v3.0.0/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:66 (include)
  C:/ncs/v3.0.0/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:97 (include_boilerplate)
  CMakeLists.txt:13 (find_package)


-- Configuring incomplete, errors occurred!
See also "D:/sensors/application/Node_1/build/Node_1/CMakeFiles/CMakeOutput.log".
See also "D:/sensors/application/Node_1/build/Node_1/CMakeFiles/CMakeError.log".
FAILED: build.ninja 
C:\ncs\toolchains\0b393f9e1b\opt\bin\cmake.exe --regenerate-during-build -SD:\sensors\application\Node_1 -BD:\sensors\application\Node_1\build\Node_1
ninja: error: rebuilding 'build.ninja': subcommand failed
FAILED: _sysbuild/sysbuild/images/Node_1-prefix/src/Node_1-stamp/Node_1-build D:/sensors/application/Node_1/build/_sysbuild/sysbuild/images/Node_1-prefix/src/Node_1-stamp/Node_1-build 
cmd.exe /C "cd /D D:\sensors\application\Node_1\build\Node_1 && C:\ncs\toolchains\0b393f9e1b\opt\bin\cmake.exe --build ."
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: 'C:\ncs\toolchains\0b393f9e1b\opt\bin\cmake.EXE' --build D:/sensors/application/Node_1/build

.

Thanks,
Amirtha N

[Marte Myrvold]

Hi Amirtha,

If you look at the build log, you can see which Kconfigs are causing issues. Look for lines mentioning undefined symbols or that a Kconfig option got a different value from what it was assigned. Here are two examples:

D:/sensors/application/Node_1/prj.conf:45: warning: attempt to assign the value 'y' to the undefined symbol WPA_SUPP

warning: WIFI_READY_LIB (defined at C:/ncs/v3.0.0/nrf\subsys\net\lib\wifi_ready/Kconfig:7) was
assigned the value 'y' but got the value 'n'. Check these unsatisfied dependencies:
WIFI_NM_WPA_SUPPLICANT (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_WIFI_READY_LIB and/or look up
WIFI_READY_LIB 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.

Please go through the migration guides and release notes, as these changes are mentioned there. For example, from Migration guide for nRF Connect SDK v2.8.0 - nRF70 Series:

• The nRF70 Series support is now part of Zephyr upstream and it requires the following changes:

  • The nRF70 Series driver namespace has been renamed from NRF700X to NRF70. For example, CONFIG_NRF700X_RAW_DATA_RX to CONIFG_NRF70_RAW_DATA_RX. Update your application configurations to use the new namespace.

  • The nRF70 Series driver now uses per-module kernel heap with a higher default. If a sample or an application uses the kernel heap but uses less than the default size, a build warning is displayed. Use the CONFIG_HEAP_MEM_POOL_IGNORE_MIN Kconfig option and enable it to suppress the warning.

• The WPA supplicant is also now part of Zephyr upstream and it requires the following changes:

  • The WPA supplicant namespace has been renamed from WPA_SUPP to WIFI_NM_WPA_SUPPLICANT. For example, CONFIG_WPA_SUPP=y to CONFIG_WIFI_NM_WPA_SUPPLICANT=y. Update your application configurations to use the new namespace.

  • You need to reconcile the application heap and kernel heap usage appropriately to accommodate this switch from application to kernel heap.

I also recommend comparing your project with samples in the SDK.

Best regards,
Marte