Simple Management Protocol module

Use the Simple Management Protocol module to perform a Device Firmware Upgrade (DFU) over Bluetooth LE.

The DFU can be performed among others using the nRF Connect Android application. The DFU button appears in the Bluetooth connected device’s tab on the Android device. After pressing the button you can select the *.bin file that will be used for the firmware update.

Note

The SMP firmware update file is generated as zephyr/app_update.bin in the build directory when building the nRF Desktop application for configuration with the MCUboot bootloader and the SMP enabled. In contrast to Device Firmware Upgrade module, the SMP does not use the zephyr/dfu_application.zip file.

Module events

Source Module	Input Event	This Module	Output Event	Sink Module
Source modules for module_state_event	module_state_event	smp
			ble_smp_transfer_event	Bluetooth LE latency module
			module_state_event	Sink modules for module_state_event

Note

See the Overview: Firmware architecture for more information about the event-based communication in the nRF Desktop application and about how to read this table.

Configuration

Make sure that the following Kconfig options are enabled:

• CONFIG_MCUMGR_CMD_IMG_MGMT The module uses MCUmgr image management handlers. See the Device Management for details about Zephyr’s device management subsystem.

• CONFIG_MCUMGR_SMP_BT The device receives SMP commands over Bluetooth.

• CONFIG_DESKTOP_CONFIG_CHANNEL_DFU_ENABLE The Device Firmware Upgrade module performs a secondary image FLASH area erase in the background and confirms the currently running MCUboot image.

• CONFIG_BOOTLOADER_MCUBOOT The DFU over Simple Management Protocol in Zephyr is supported only with the MCUboot bootloader.

Enable the module using the CONFIG_DESKTOP_SMP_ENABLE Kconfig option.

Implementation details

During the initialization, the module registers the SMP Bluetooth service.

The module registers the upload_confirm() callback that is used to confirm or reject the image upload. The image upload is rejected only if the Device Firmware Upgrade module has called the dfu_lock() function. You can find the header file of the dfu_lock() at the following path: src/util/dfu_lock.h. Before the image is received through the SMP, the Simple Management Protocol application module calls the lock function. Also, firmware updates through the Device Firmware Upgrade module are disabled until the nRF Desktop device is rebooted. The modification of the data in the secondary image slot, by any other application module during the ongoing DFU, would result in a broken firmware image that would be rejected by the bootloader.

The module periodically submits ble_smp_transfer_event while the image is being uploaded. Bluetooth LE latency module decreases the connection slave latency when it receives this event. This is done to speed up the data transfer.