SMP server

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Overview

This sample application implements a Simple Management Protocol (SMP) server. SMP is a basic transfer encoding for use with the MCUmgr management protocol. For more information about MCUmgr and SMP, please see Device Management.

This sample application supports the following MCUmgr transports by default:

  • Shell

  • Bluetooth

  • UDP

smp_svr enables support for the following command groups:

  • fs_mgmt

  • img_mgmt

  • os_mgmt

  • stat_mgmt

  • shell_mgmt

Caveats

  • The MCUboot bootloader is required for img_mgmt to function properly. More information about the Device Firmware Upgrade subsystem and MCUboot can be found in MCUboot.

Prerequisites

Use of a tool

To interact remotely with the management subsystem on a device, a tool is required to interact with it. There are various tools available which are listed on the Tools/libraries page of the Management subsystem documentation which can be used as a client for a Zephyr MCUmgr SMP server.

Building a BLE Controller

Note

This section is only relevant for Linux users

If you want to try out Device Firmware Upgrade (DFU) over the air using Bluetooth Low Energy (BLE) and do not have a built-in or pluggable BLE radio, you can build one and use it following the instructions in Using the controller with BlueZ.

Building the sample application

The below steps describe how to build and run the smp_svr sample in Zephyr with MCUboot included. The smp_svr sample comes in different flavours.

To build the bluetooth sample:

west build -b nrf52dk/nrf52832 --sysbuild samples/subsys/mgmt/mcumgr/smp_svr -- -DEXTRA_CONF_FILE="overlay-bt.conf"

Flashing the sample image

The original application will be built for slot-0, see Flash map for details on flash partitioning. Flash both MCUboot and the sample application:

west flash

Sample image: hello world!

The smp_svr app is ready to run. Just reset your board and test the app with your choice of tool’s echo functionality, which will send a string to the remote target device and have it echo it back.

Device Firmware Upgrade (DFU)

Now that the SMP server is running on your board and you are able to communicate with it using a client, you might want to test what is commonly called “OTA DFU”, or Over-The-Air Device Firmware Upgrade. This works for both BT and UDP.

The general sequence of a DFU process is as follows:

  • Build an MCUboot enabled application using sysbuild, see Building the sample application

  • Upload the signed image using an MCUmgr client

  • Listing the images on the device using an MCUmgr client

  • Mark the uploaded image for testing using an MCUmgr client

  • Reset the device remotely using an MCUmgr client

  • Confirm the uploaded image using an MCUmgr client (optional)

Direct image upload and Image mapping to MCUboot slot

Currently MCUmgr supports, for direct upload, 4 target images, of which first two are mapped into MCUboot primary (slot-0) and secondary (slot-1) respectively.

For clarity, here is DTS label to slot to <image> translation table:

DTS label

Slot

-n <image>

“image-0”

slot-0

1

“image-1”

slot-1

0, 1

“image-2”

2

“image-3”

3

Note

There is a slot info command that can be used to see information on all slots and get the upload image ID to use to update that slot, see Slot info for details.

Upload the signed image

To upload the signed image, refer to the documentation for your chosen tool, select the new firmware file to upload and begin the upload.

Note

At the beginning of the upload process, the target might start erasing the image slot, taking several dozen seconds for some targets.

List the images

A list of images (slot-0 and slot-1) that are present can now be obtained on the remote target device using the tool of your choice, which should print the status and hash values of each of the images present.

Test the image

In order to instruct MCUboot to swap the images, the image needs to be tested first, making sure it boots, see the instructions in the tool of your choice. Upon reboot, MCUBoot will swap to the new image.

Note

Some tools may allow for listing the hash of an image without needing to upload them. imgtool can also be used to list the image hash, albeit in a C hex-array format, by using the dumpinfo command on the signed update file, e.g.

imgtool dumpinfo smp_svr/zephyr/zephyr.signed.bin

Printing content of signed image: zephyr.signed.bin

#### Image header (offset: 0x0) ############################
magic:              0x96f3b83d
...
#### TLV area (offset: 0xbfa0) #############################
magic:     0x6907
area size: 0x150
        ---------------------------------------------
        type: SHA256 (0x10)
        len:  0x20
        data: 0x9b 0xa9 0x84 0x48 0xe5 0x4d 0xac 0x40
              0x62 0x29 0xe2 0x11 0x17 0x96 0x66 0xd9
              0xae 0x83 0x9a 0x37 0x71 0x00 0xfc 0xe2
              0xc0 0x30 0x30 0x4f 0xfc 0x40 0x58 0xaa
        ---------------------------------------------
...

The full SHA256 hash for the above output would be: 9ba98448e54dac406229e211179666d9ae839a377100fce2c030304ffc4058aa

Reset remotely

The device can be reset remotely to observe (use the console output) how MCUboot swaps the images, check the documentation in the tool of your choice. Upon reset MCUboot will swap slot-0 and slot-1.

Confirm new image

The new image is now loaded into slot-0, but it will be swapped back into slot-1 on the next reset unless the image is confirmed. Confirm the image using the tool of your choice.

Note

If you try to send the very same image that is already flashed in slot-0 then the procedure will not complete successfully since the hash values for both slots will be identical.

Download files from/upload files to file system

SMP server supports downloading files from/uploading files to the on-device File Systems, this is useful with e.g. FS log backend, when files are stored in non-volatile memory. Build and flash smp_svr using sysbuild and then use the tool of your choice to download files from the file system. The full path of the file on the device must be known and used.