"Many low-power wireless interfaces and protocols, such as low-power Bluetooth, ZigBee, thread, etc., are common in smart home and smart industrial sensor mesh applications. However, developers found that these RF protocols were designed before the advent of the Internet of things (IOT), so they usually lack interoperability with internet protocol (IP) IPv4 and IPv6, which makes it challenging to connect relevant designs with IOT to achieve the goal of intelligent sensing, automation and control.
There are many ways to solve the problem of IP interoperability, such as converting data packets or using IP compatible wireless interfaces. The first option is inefficient, and the second reduces the designer's Wi Fi selection range.
This article will focus on the third way: IOT gateway. They can be used as network aggregators and usually have advanced security and a variety of I / O backhaul options. This article will describe its functions and features, then introduce the appropriate solution and how to maximize its role.
Wireless options for IOT
Despite the lack of direct IP interoperability, many popular low-power wireless interfaces and protocols have good range and throughput, coexistence with other 2.4 GHz technologies, and mesh network support（ See digi key article "comparison of low power wireless technologies.")
Two way wireless connection enables users to remotely monitor and control the system, and analyze process data through powerful cloud based algorithms to achieve the objectives of optimizing performance, saving energy or improving productivity.
As mentioned earlier, there are three ways to overcome the lack of IP interoperability of low-power wireless protocols. The first is to select the protocol with network adaptation layer, which can "convert" data packets so that they can be transmitted through IPv6 network. Some manufacturers provide low-power Bluetooth, ZigBee, thread and other RF Protocol "stacks" including IPv6 Based low-power wireless personal area network (6LoWPAN) transport layer. Generally, these protocol stacks can work normally, but the implementation is more complex, and each node needs more processor resources and power consumption.
The second option is to use a wireless protocol with local IP support. Wi Fi may be the best example. Strictly speaking, Wi Fi only defines the physical (PHY) layer, media access control (MAC) layer and logical link control (LLC) layer of the protocol stack. However, Internet Wi Fi connections are everywhere, and suppliers usually provide a complete TCP / IP protocol stack based on the lower layer of Wi Fi. The cost is that Wi Fi nodes are larger, more expensive, and have higher power than other competing wireless technologies, so they are not suitable for all applications.
The third method is to use IOT gateway. These devices are self-contained devices, including all the software and hardware needed to bridge the gap between LAN and IOT (Figure 1). Gateway is also a good choice for developers with limited RF expertise or those who want to increase Internet connectivity in traditional low-power wireless networks.
Figure 1: designers can choose from three schemes for connecting wireless sensor networks to IOT. The first selection shown here describes how to connect the wireless node to the IOT gateway to connect it to the Internet as a relay（ Image source: Texas Instruments)
Differences between gateways and routers
It is necessary to distinguish between gateway and router. Router is a simpler device. It serves nodes, shares a common protocol, and needs to separately transfer the data transmitted through the protocol to and from the Internet. Wi Fi router is a good example; These devices route data between IP enabled mobile devices (such as smartphones and laptops) and the Internet, but do not interact.
In contrast, IOT gateway integrates data from different wireless sources and interfaces and connects it to the Internet. In some cases, the gateway is used in conjunction with the router to facilitate implementation. The main advantage of gateway is that it does not need independent network nodes, so it supports IP with its related complexity and cost characteristics.
Gateways can be simple or complex. The simple device organizes and "converts" the packets received by the node, making it suitable for transmission on the Internet. Moreover, a simple gateway can convert the data packets received from the Internet and distribute them to each node in the network.
More complex gateways not only have this function, but also have advanced security features and resources to handle all or part of the application process (sharing load with nodes). The advantage of the system is that the nodes are simpler, cheaper and lower power consumption. In a system with many nodes, the cost of concentrating processing power on the gateway is lower than distributing it to all nodes. More complex gateways also ensure that the LAN continues to work when Internet access is interrupted, and can buffer node data for cloud transmission when Internet access is re established.
Gateway solution
Many manufacturers offer commercial IOT gateway solutions. Devices are usually mains powered devices that can be configured to use a variety of wireless interfaces, including the selection of low-power RF protocols. Generally, IOT is connected through IP based wireless wide area network (WAN) interfaces such as Wi Fi (or wired types such as Ethernet). Some newer designs include Internet access through cellular networks or proprietary WAN technologies such as lorawan.
WAN technology usually adopts heavyweight protocol stack controlled by operating system (OS) such as Linux. In order to meet the computing requirements of such firmware, commercial IOT gateways are equipped with powerful embedded microcontrollers.
More advanced gateways support multiple network platforms, such as hsdk, nat64, PC ble serialization and lorawan gateway bridge, as well as a variety of cloud services, such as those of Amazon, Microsoft, Ayla and IBM. These advanced devices also have features such as remote management of application installation, firmware update and configuration change, terminal device firmware update, and remote management of mesh network topology and devices.
Rigado's Vesta series IOT gateways are a good example of the latest generation of configurable gateways. The product is powered by NXP i.mx6 Ultralite arm running yocto Linux OS ® Cortex ®- A7 provides support for application processors. The device supports 2.4 and 5 GHz Wi Fi (IEEE 802.11a / B / g / N), Bluetooth 4.2, low-power Bluetooth and IEEE 802.15.4 (including thread). The gateway also supports Ethernet powered by IEEE 802.3af Ethernet (POE) and USB 2.0. The gateway requires a 4.5 to 5.5 V power supply or operates through a Poe connection. According to rigado, cellular and lorawan expansion options will be provided soon.
Sierra wireless's fx30 IOT gateway also has arm ® Cortex ®- A7 application processor with open source yocto Linux OS (Figure 2). The Internet connection is realized through the cellular infrastructure (LTE cat 1), and the device can receive Wi Fi, Bluetooth and ZigBee inputs from the IOT connector expansion slot. Standard units are designed to use wired interfaces, such as Ethernet and USB only, and require a 4.75 to 32 V power supply. The low power consumption of the device is remarkable, the power consumption in standby mode is less than 1 W, and the power consumption in sleep mode is only 2 MW, which is firm and durable. The device meets the vibration and mechanical shock requirements of mil-std-810, and the operating temperature range is from - 30 ° to + 75 ° C. It is a good choice for industrial applications.
Figure 2: fx30 IOT gateway of Sierra wireless connects to the Internet using cellular technology（ Image source: Sierra wireless)
A third example of a commercial IOT gateway comes from Laird Technologies. Its sentrius rg1xx series is famous for using lorawan, a long-distance low-power WAN technology connected to the Internet. The device adopts ATMEL A5 embedded microprocessor and runs Linux OS. In addition to lorawan, the device also provides 2.4 and 5 GHz Wi Fi, Bluetooth 4.0 and low-power Bluetooth interfaces and Ethernet interfaces. Due to the long-distance connection, sentrius is very suitable for smart meters, industrial automation and agricultural applications.
Debug gateway
IOT gateways such as rigado, Sierra wireless and Laird Technologies allow designers to connect their low-power wireless networks to the Internet and cloud services without designing complex connection hardware and firmware. However, some development work is needed to ensure seamless operation. Fortunately, IOT gateway manufacturers usually provide products, tools and services that facilitate this development process.
For example, Laird's sentrius is specifically designed to connect the company's rm186 / 191 series lorawan / Low-Power Bluetooth wireless module for wireless sensor applications. These devices combine convenience and low-power Bluetooth smartphone interoperability, and lorawan extends up to 15 km. Laird provides the development kit dvk-rm186-sm-01 to simplify the process of connecting modules to the sentrius gateway. Using the company's node red development environment and relevant guidelines, the process becomes more direct and clear.
Sierra wireless recommends using the legato open source Linux platform to connect its fx30 IOT gateway to the cloud. Legato has an application "sandbox" that provides a secure environment for running and controlling multiple applications. The platform also provides application programming interfaces (APIs) that enable developers to connect to the cloud.
For developers who need to design advanced networks, legato provides an eclipse based integrated development environment (IDE) with multilingual support and a set of diagnostic tools to start local and remote debugging, troubleshooting, monitoring and analysis.
Send data to cloud
Rigado has further simplified wireless network and cloud connectivity through its vg3-23e4-wib0c0-asa-dek IOT development kit, including Vesta gateway and Nordic thing: 52 Low Power Bluetooth development kit (Figure 3). The development kit allows engineers to design prototype solutions that connect Bluetooth 5 / Low-Power Bluetooth sensors to the cloud. The advantage of using the IOT development kit is that no RF experience is required because the thingy: 52 sensor is configured to communicate with Vesta gateway. Since rigado's node red development environment includes demonstration applications, the data of thingy: 52 sensors can be forwarded to Amazon Web services (AWS) cloud services through Vesta gateway, and the prototype design is further simplified.
The method of sending Nordic thingy: 52 sensor data to AWS through Vesta gateway is straightforward. Vesta is first configured as a Wi Fi access point and connected to the developer's Wi Fi network through a browser. Click the URL provided to launch the node red application, which then automatically scans Nordic thingy: 52 to try to connect and scan the universal unique identifier (UUID). After the connection is established, the sensor data is read from Nordic thingy: 52 and sent to AWS and node red application dashboard. Developers can make changes through the dashboard to filter the information to be transmitted and the frequency of transmission.
The node red development environment also provides an easy way for experienced developers to create browser based workflows to connect hardware devices, application programming interfaces (APIs) and cloud services.
Connecting the sensor network to the cloud through IOT gateway can multiply the utilization of the system. Cloud service providers usually provide infrastructure to process sensor raw data, control and analyze data, and provide useful information or feedback from it.
For example, when using AWS cloud system, Vesta gateway connects to AWS API gateway (Figure 4). Through the API gateway, developers can create, configure and host APIs for Vesta gateway applications to access the cloud. For example, applications can upload temperature and humidity data from Nordic thingy: 52 built-in sensors using the API. The raw data can then be stored in Amazon S3 "buckets" or Amazon dynamodb database services.
Figure 4: Vesta gateway uses Amazon's AWS cloud service to collect data and run all relevant code（ (source: rigado.)
Another part of AWS, AWS lambda, provides computing services that allow developers to run cloud based code without preparing or managing servers. AWS lambda supports node.js, Java, c# and python.
For example, developers can use the code running on AWS lambda to announce temperature and humidity extremes and daily, weekly and monthly averages using the raw data sent by Nordic thing: 52.
Configuring AWS lambda to run code in response to trigger events is relatively straightforward, such as making specific changes to data in buckets or databases. For example, developers can choose to run a set of codes to send notifications to smartphones when the temperature or humidity exceeds a set threshold.
After the prototype design is completed, rigado semiconductor based Nordic can be used The module family (for Bluetooth 5 / Bluetooth low-power wireless sensor network applications) replaces Nordic thingy: 52 to form the final production design.
summary
Cloud connectivity is critical to maximizing the benefits of intelligent wireless technology
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