samples: bluetooth: mesh: add external flash for dfu distributor

Commit adds ability to use the external flash as
the secondary partition to store image and then
distribute it as well as update distributor by self.
External flash is supported only for nrf52840 DK.

Signed-off-by: Aleksandr Khromykh <[email protected]>

Author: alxelax

samples/bluetooth/mesh/dfu/distributor/README.rst

@@ -237,6 +237,25 @@ In this sample, the UART console is occupied by the shell module.
 Therefore, it uses SEGGER RTT as a logging backend.
 For the convenience, ``printk`` is also duplicated to SEGGER RTT.
 
+External flash support
+======================
+
+This sample supports external flash memory as secondary storage partition for saving of the firmware images, both as for self update as well as for distribution.
+See :ref:`ug_bootloader_external_flash` for more information on external flash support as a partition in the :ref:`ug_bootloader_mcuboot_nsib`.
+The default configuration does not support external flash memory.
+To enable external flash support, set :makevar:`FILE_SUFFIX` to ``ext_flash`` when building the sample.
+
+Build the sample using the following command:
+
+.. code-block:: console
+
+   west build -p -b *board_name* -- -DFILE_SUFFIX=ext_flash
+
+.. note::
+   The external flash is not erased during the internal flash erasing procedure.
+   See `nRF Util`_ for more information on how to erase the external flash.
+   Currently, only the external flash on the ``nrf52840dk/nrf52840`` board is supported at the moment.
+
 Dependencies
 ************
 

samples/bluetooth/mesh/dfu/distributor/sample.yaml

@@ -32,3 +32,15 @@ tests:
       - bluetooth
       - ci_build
       - sysbuild
+  sample.bluetooth.mesh_dfu_distributor.ext_flash:
+    sysbuild: true
+    build_only: true
+    integration_platforms:
+      - nrf52840dk/nrf52840
+    platform_allow:
+      - nrf52840dk/nrf52840
+    extra_args: FILE_SUFFIX=ext_flash
+    tags:
+      - bluetooth
+      - ci_build
+      - sysbuild

samples/bluetooth/mesh/dfu/distributor/sysbuild/distributor_ext_flash.overlay

@@ -0,0 +1,10 @@
+/* Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		nordic,pm-ext-flash = &mx25r64;
+	};
+};

samples/bluetooth/mesh/dfu/distributor/sysbuild/mcuboot.conf

@@ -1,3 +1,9 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+################################################################################
 # RTT is used for interacting with the distributor over shell. Having it enabled in mcuboot will
 # require a user to manually provide correct _SEGGER_RTT address otherwise RTT Viewer will pick
 # wrong buffer and shell will not work.

samples/bluetooth/mesh/dfu/distributor/sysbuild/mcuboot_ext_flash.conf

@@ -0,0 +1,17 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+################################################################################
+# RTT is used for interacting with the distributor over shell.
+# Having it enabled in mcuboot will require a user to manually provide correct _SEGGER_RTT address.
+# Otherwise RTT Viewer will pick wrong buffer and shell will not work.
+CONFIG_USE_SEGGER_RTT=n
+
+CONFIG_NORDIC_QSPI_NOR=y
+CONFIG_NORDIC_QSPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096
+CONFIG_NORDIC_QSPI_NOR_STACK_WRITE_BUFFER_SIZE=16
+
+# Maximum number of sectors that image can have
+CONFIG_BOOT_MAX_IMG_SECTORS=256

samples/bluetooth/mesh/dfu/distributor/sysbuild/mcuboot_ext_flash.overlay

@@ -0,0 +1,11 @@
+/* Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		zephyr,code-partition = &boot_partition;
+		nordic,pm-ext-flash = &mx25r64;
+	};
+};

samples/bluetooth/mesh/dfu/distributor/sysbuild_ext_flash.conf

@@ -0,0 +1,11 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+SB_CONFIG_BOOTLOADER_MCUBOOT=y
+SB_CONFIG_PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY=y
+SB_CONFIG_DFU_ZIP=y
+SB_CONFIG_DFU_ZIP_BLUETOOTH_MESH_METADATA=y
+SB_CONFIG_DFU_ZIP_BLUETOOTH_MESH_METADATA_FWID_MCUBOOT_VERSION=y