Set Up Basic LWM2M System

Now that you have installed the Zephyr and Linux microPlatforms, it’s time to use them to set up an end-to-end IoT demonstration system using the OMA Lightweight M2M (LWM2M) protocol.

A block diagram of this system is shown here. Though it is not explicitly shown, one or more IoT devices can connect to the network through the same gateway.

LWM2M System Diagram

The system contains Zephyr-based IoT devices, a Linux-based IoT gateway, and a web application, Leshan, that is used as the LWM2M server. With Leshan, you can issue commands, query data, and perform firmware over the air (FOTA) updates on the IoT device(s).

Using the demonstration system described here, you can:

  • See live data readings from your devices using the Leshan web application.
  • Send commands to the device, such as turning on and off an LED.
  • Use Leshan to update your IoT device firmware.

For simplicity, this basic system does not secure its network communications. Instructions in the next page describe how to set up secure channels using the DTLS protocol.

Prepare the System

Set up IoT Gateway

The gateway-containers project includes a simple docker-compose file that can start up a minimal set of containers to support this tutorial. Log into your gateway using SSH and then run:

git clone https://github.com/foundriesio/gateway-containers.git

cd gateway-containers
docker-compose up -d

You can watch the logs of the containers with:

# From your gateway-containers directory:
docker-compose logs -f            # tail logs from all containers
docker-compose logs -f bt-joiner  # tail logs for a single container

To get a list of running containers, use docker ps.

Your gateway device is now ready for use.

Set up IoT Device(s)

Build and flash the demonstration application for your board:

BLE Nano 2

./zmp build -b nrf52_blenano2 zephyr-fota-samples/dm-lwm2m
./zmp flash -b nrf52_blenano2 zephyr-fota-samples/dm-lwm2m

nRF52 DK (nRF52832)

./zmp build -b nrf52_pca10040 zephyr-fota-samples/dm-lwm2m
./zmp flash -b nrf52_pca10040 zephyr-fota-samples/dm-lwm2m

nRF52840 DK

./zmp build -b nrf52840_pca10056 zephyr-fota-samples/dm-lwm2m
./zmp flash -b nrf52840_pca10056 zephyr-fota-samples/dm-lwm2m

Use the System

Now that your system is fully set up, it’s time to check that sensor data are being sent to the cloud, and do a FOTA update.

Look in your IoT device console for a log line ending in something like this:

LWM2M Endpoint Client Name: zmp:sn:deadbeef

Above, the value zmp:sn:deadbeef is your device’s client ID, which it uses to register with the LWM2M server. Look for that ID in the clients list at https://mgmt.foundries.io/leshan/#/clients, and click on it to view available LWM2M objects on your device.

Note

This LWM2M server interface is provided by Foundries.io only for ease of use bringing up the system and prototyping. Availability etc. are not guaranteed.

Read and Write Objects

When a device registers with the Leshan server, Leshan will automatically render known object types in its web interface. You can interact with these objects by clicking the Read, Write, etc. buttons which appear next to them.

  • Read device instance information

    To read general device instance information, scroll down to “Device” > “Instance 0” and click the “Read” button as shown in the following figure.

    Instance 0 information

    Click on the Read button following “Instance 0”.

  • Read current state of temperature and light objects

    To read the current status of the temperature and light control objects, click the “Read” button next to each “Instance” of these objects as shown in the following figure.

    Read the light settings in Leshan

    Click on the Read buttons following the instances.

  • Change state of the light object

    Click “Write” buttons to bring up interfaces for changing data. An example of this interface for the light object is shown here.

    Write the light settings in Leshan

    Clicking the On/Off Write button brings up this interface.

Initiate a Firmware Update

It’s now time to update the device firmware, using the Firmware Update object view in Leshan. This involves writing a URI where the firmware update is hosted to the “Package URI” field for this object. To keep things simple, you’ll “update” the firmware using the same binary you built previously, but you can also change and rebuild the program before following these steps to write new firmware.

Start a Python 3 HTTP server on your workstation from the Zephyr microPlatform binary build directory for your board:

BLE Nano 2

cd build/zephyr-fota-samples/dm-lwm2m/nrf52_blenano2/app/
python3 -m http.server

The update will then be available at:

http://YOUR_WORKSTATION_IP:8000/zephyr/dm-lwm2m-nrf52_blenano2-signed.bin

nRF52 DK (nRF52832)

cd build/zephyr-fota-samples/dm-lwm2m/nrf52_pca10040/app/
python3 -m http.server

The update will then be available at:

http://YOUR_WORKSTATION_IP:8000/zephyr/dm-lwm2m-nrf52_pca10040-signed.bin

nRF52840 DK

cd build/zephyr-fota-samples/dm-lwm2m/nrf52840_pca10056/app/
python3 -m http.server

The update will then be available at:

http://YOUR_WORKSTATION_IP:8000/zephyr/dm-lwm2m-nrf52840_pca10056-signed.bin

(Adjust the above as needed for other boards.)

To start the firmware update, click the Write button for the “Package URI” field in the Firmware Update object, then write this value in the resulting popup, like so.

User interface for setting Package URI

Set the Package URI field.

Once you click the Update button, the file will begin transferring to the target.

In general, the Package URI must be hosted where it is routable from your IoT device. The URI schema can be either coap:// or http://. The length of the Package URI must be less than 255 characters.

Monitor for a Completed Transfer

Click the “Observe” button in the State line of the Firmware Update object:

Leshan interface showing State value equal to 1

Example State observation. Value is 1 (downloading).

The state values and their meanings are:

  • 0: Idle
  • 1: Downloading
  • 2: Downloaded
  • 3: Updating

If you’re connected to the device console, progress is logged as in the following example:

[0912360] [fota/lwm2m] [INF] firmware_block_received_cb: 77%
[0920080] [fota/lwm2m] [INF] firmware_block_received_cb: 78%
[0927350] [fota/lwm2m] [INF] firmware_block_received_cb: 79%
[0931870] [lib/lwm2m_rd_client] [INF] do_update_reply_cb: Update callback (code:2.4)
[0931870] [lib/lwm2m_rd_client] [INF] do_update_reply_cb: Update Done
[0932510] [fota/lwm2m] [INF] firmware_block_received_cb: 80%
[0939070] [fota/lwm2m] [INF] firmware_block_received_cb: 81%
[0946090] [fota/lwm2m] [INF] firmware_block_received_cb: 82%
[0951050] [fota/lwm2m] [INF] firmware_block_received_cb: 83%

Monitor the transfer until the State value is 2 (Downloaded):

Leshan interface showing State value equal to 2

State value is now 2 (Downloaded).

Download completion is logged on the device console as in the following example:

[1073870] [fota/lwm2m] [INF] firmware_block_received_cb: 98%
[1078930] [fota/lwm2m] [INF] firmware_block_received_cb: 99%
[1085540] [fota/lwm2m] [INF] firmware_block_received_cb: 100%

Execute the Update

After the device has downloaded the update file, initiate the update by clicking on the “Exec” button on the Update line.

The device console logs messages as it resets into the bootloader, MCUBoot, which will load the new image:

[1171230] [fota/lwm2m] [DBG] firmware_update_cb: Executing firmware update
[1171230] [fota/lwm2m] [INF] firmware_update_cb: Update Counter: current -1, update -1
[1172260] [fota/lwm2m] [INF] reboot: Rebooting device
[MCUBOOT] [INF] main: Starting bootloader
[MCUBOOT] [INF] boot_status_source: Image 0: magic=good, copy_done=0xff, image_ok=0x1
[MCUBOOT] [INF] boot_status_source: Scratch: magic=unset, copy_done=0x2f, image_ok=0xff
[MCUBOOT] [INF] boot_status_source: Boot source: slot 0
[MCUBOOT] [INF] boot_swap_type: Swap type: test
[MCUBOOT] [INF] main: Bootloader chainload address offset: 0x8000
[MCUBOOT] [INF] main: Jumping to the first image slot
***** BOOTING ZEPHYR OS v1.9.99 - BUILD: Nov  8 2017 22:04:52 *****
[0000000] [fota/main] [INF] main: Linaro FOTA LWM2M example application
[0000010] [fota/main] [INF] main: Device: nrf52_blenano2, Serial: 1ef8e685

When the update execution is complete, the device will register with Leshan again.

Congratulations! You’ve just read and written objects, and done your first FOTA update using this system. Continue to the next page to secure LWM2M communications using DTLS.

Reporting Issues

Please report any issues to the Foundries.io Support Portal.