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This guide provides design guidelines for developing an application on top of the 6LoWPAN mesh solution. The APIs and technologies are not discussed in detail here. The nodes are connected to a cloud service for feeding in the sensor or control data. The colours in the illustrations represent different device types and are used in the examples throughout this tutorial. Arm does not provide translation to IPv4 network due the limited address space.
We recommend using IPv6 tunnels over IPv4 network when operating in such environment. The border router also authenticates the nodes joining the network and keeps track of the routing topology.
This role is required to form a topological or mesh network. This configuration does not allow nodes to sleep because they route packets to their siblings. It has only one parent routing the packets. Depending on the business requirements and use cases the network may have different setups and requirements.
Star topology is the simplest form of a mesh network. Actually, it is not mesh at all. Every node connects directly to the border router. In a star network, nodes can be very low-power devices with least amount of RAM because they have no routing responsibilities.
It also allows sleeping nodes. Every node selects a primary parent for routing so the result looks like a tree. This network type allows to cover large areas because each node extends the range of the network.
However, the packet is retransmitted on every hop, which means that the transfer capacity of the network decreases as the size of the network increases. Thread was designed with one goal in mind; to create the best way to connect and control products in home.
The key features of Thread are:. Internet Protocol IP provides the core mechanism for relaying datagrams across IP networks, and its routing capabilities enable internetworking. Mbed OS is an open source embedded operating system designed specifically to facilitate the creation and deployment of commercial, standards-based IoT solutions at scale. Mbed OS features full support for Thread to simplify development of secure IoT applications in home and to ease the Thread product certification.
Nanostack provides a set of C API headers with more functionalities. The nanostack repository has the following header files:. In a SED device, the radio is switched off during the sleep times. To take the full advantage of the SED configuration, the application developer must implement the sleep procedures in the device. For an end device or a router example, see mesh minimal example. Mbed OS offers separate configurations for different Thread end device types.
Usually, the end devices are the most constrained devices in the Thread network. They serve as last hop in the mesh topology. Devices such as plain sensors, controls and switches can be implemented as end devices only. For the most constrained hardware, the minimal end device MED or the sleepy end device SED is an optimal selection as the implementation requires the smallest amount of flash and RAM memory due to the limited functionality.
Note that a sleepy end device also requires more resources on the parent device. End devices communicate through a parent and can switch to another parent if the current connection is broken. A Thread network does not work with end devices only. There must be router devices, that can route the traffic between nodes and to the back-end network through the border router.
In Thread networks, devices operate in several specific roles separated by the services they provide. All router devices provide mesh routing and they can switch the state between an active router and a REED device without any user interaction. The first router on a network becomes a leader, that manages:. Additionally, a router can act as a border router must be configured in build time , that provides services for devices within the Thread mesh network and the backbone network.
Mbed OS offers a separate build for a Thread border router. The border router routes IPv6 traffic to the external IPv6 networks. Currently, our border router uses an Ethernet connection to the backbone IP network, but also other means of connectivity are available cellular or WiFi.
See an example of a Thread border router. Commissioning takes place when new devices need to be added to the Thread network.
In Thread, there can be one commissioner, that allows new devices to join the network. There are three types of commissioners:. When you select the network to connect to, the application asks for the network passphrase. The passphrase is usually placed on a label on the border router box like in WiFi. After the authentication phase, the commissioner requests the Thread network leader to petition the commissioner to become an authorized commissioner.
Here, the border router works as an arbitrator in the middle. Thread uses hashing and elliptic curve algorithms for the secure communication. The Mbed OS Thread stack supports all three types of commissioners. Currently, there is no reference implementation for native or on-mesh commissioners. External commissioning is supported through the Nanostack border router. An external Commissioning application Android is already available.
Also an IOS version will be available soon. See Thread commissioning guide how to commission a Thread device to the network in practice. In addition to the Thread Group certification, where the focus is to ensure interoperability with different implementations, the Arm Mbed team is focused on delivering a high quality implementation of the software components required in the Thread implementation.
We have invested in the automated test environment, where we can verify all the change requests as well as the regular releases. The data rate available per node should be considered when designing the application. Basically, the data rate is divided between all nodes in the network.
Roughly half of the channel capacity should be allocated for signalling purposes, and each hop requires retransmisson of the packet. The bandwidth per node is divided by the number of nodes in the network and the number of hops. As the stack runs on multiple different Mbed OS development boards there might be combinations of board and RF shields that may, or may not, work together due to pin collision or other reasons.
Please see Notes on different hardware on Mesh example application for up to date copy of this list. The following table shows which development boards have been tested.
It does not present our current testing infrastructure, so we cannot guarantee all combinations but we do our best to ensure it is up to date. They will differ based on the toolchains or the status of the repository. The final size can only be estimated when linking the final application.
The indicated size only gives you a guideline of what kind of changes to expect between different options. If you want to optimize the flash usage, you need to select a proper configuration for Nanostack. The configuration depends mostly on the preferred use case. These same principles apply also to Thread protocol. Then you may optionally choose to select the non-routing mode for those networks.
If you want to use the Thread commissioning, add the following lines to your. You can use the mesh-minimal application as an example. Setting thread-use-static-link-config to false prevents the usage of the predefined link configuration values and allows the device to start network scanning. You can use a free online tool to generate a QR code. In the tool, fill in the URL field: These are just example values. To print the MAC address, you need to connect the node to the Thread network with static configuration enabled, unless you have your own configuration for the MAC address.
You can use the Thread Android application for commissioning:. There are no different commissioning modes for devices joining to the network, there are only different kinds of commissioners on-mesh, native, external.
Thread devices either have the configuration or not. Then they do the commissioning using DTLS to authenticate themselves and if successful, they will receive the network credentials and become a part of the network. The commissioner can modify the configuration at any time. The manufacturer does not decide the Thread link configuration.
Ad-hoc networks with devices from different manufacturers can be easily created by commissioning. An example application is downloadable from the Android store. The mesh minimal uses socket communication and multicasting. See more details in the mesh minimal example. Thread is based on the IPv6 protocol.
If the communication must go over IPV4 network, there are two solutions available:. There are no special Thread codes available, you will have the normal internet error codes. An application must handle the temporary network connection problems with proper retry logic. IPv6 multicast messages are supported.