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A Cloud Link for Energy Harvesting Wireless Networks
The ready-made middleware EnOcean Link provides a universal interface between energy harvesting wireless solutions and any automation application.
|Marian Hönsch, Product Marketing – Software Architect, EnOcean GmbH|
Link is a
middleware for energy harvesting wireless networks.
It transforms EnOcean telegrams into ready-for-use data which eases the
integration of energy harvesting wireless solutions into a wide range
of applications and networks, thus facilitating the development of
deeply interconnected systems. Using EnOcean Link as a web service via
the Internet moves the effort of processing to the cloud, enabling
lightweight cost-efficient gateways.
In today’s deeply
connected world, there is an increasing demand to
incorporate batteryless devices into networks based on several
different communication standards such as WiFi, GSM, Ethernet/IP,
BACnet, LON, KNX or DALI. With EnOcean Link, product manufacturers
(OEMs) can easily transfer energy harvesting wireless signals into the
requested communication protocol.
Interpretation of data
The ready-made middleware EnOcean Link provides a universal interface between energy harvesting wireless solutions and any automation application that further processes the wireless information. Therefore, the software converts the bits and bytes of an EnOcean telegram directly into data values. As a result, sensor data such as humidity or temperature is prepared so that different devices, servers and even cloud services can process it immediately. OEMs can now integrate energy harvesting wireless technology easier and faster into a wide range of applications and systems, such as those found in building automation.
A middleware is a separate piece of software which functions as a
connective link between different systems or applications. It does not
contribute to the application itself but enables the application to
understand the messages from all components and systems in a network,
even when they are based on different standards. This seamless
communication is enabled because the different protocols address
similar use cases (e.g. building automation). This eases the
combination of several functionalities and applications to a more
beneficial technical framework. EnOcean Link resembles a library, which
offers services for other layers. By using the software, developers
gain control of the execution order, of inbound and outbound
communication interfaces and the data storage.
However, the main functionalities of the middleware are to
automatically take into account all specifications of the EnOcean
protocol stack, the application profiles (EnOcean Equipment Profiles,
EEPs) and Generic Profiles of the EnOcean Alliance as well as data
encryption mechanisms. Generally speaking, the software has the
following three key tasks:
Values for further processing
The protocol (EnOcean Serial Protocol 3.0; ESP3) describes the serial
communication between a host and energy harvesting wireless receivers,
such as an EnOcean USB dongle. Hosts are external microcontrollers or
PCs that include application-specific software tools. ESP3 is a
point-to-point protocol with a packet data structure. This protocol
encapsulates actual user data (payload), command, event or response
Every ESP3 packet consists of telegram header, data and optional
data. Each of these groups consists of fields with 1 or x bytes.
The packet header, for example, is composed of the fields: data length
(number of bytes of the data group), optional length (number of bytes
of the group optional data) and the packet type (e.g. radio, response,
EnOcean Link middleware provides several service layers to operate an
energy harvesting wireless sensor network. These service layers are
connected together to provide a clear user interface. On the physical
layer, EnOcean Link receives the UART data stream (Universal
Asynchronous Receiver/Transmitter) from the gateway. The ESP3 encoder
is located over the physical layer. This layer handles all necessary
operations to prepare the telegram data fields into a suitable form for
The profile interpreter, based on the stored application profiles, interprets the telegram payload into human readable values such as temperature or humidity. These values are presented as the so-called device channels. These are made available to the application through the API interface, which can be called directly from the application’s source code or through a tunneling protocol that encapsulates EnOcean Link. The device profiles, being how the device transmits and codes its values, are described in the EEPs or Generic Profiles.
EnOcean Link in the Cloud
OEMs can use the middleware for any gateway application to integrate
energy harvesting wireless devices and systems into a broader network.
The signal of the UART data stream can come directly from a gateway or
can be provided by a backbone which was optionally tunneled before to
forward the encapsulated payload protocol. So, for a scenario with
simple and cost-effective gateway solutions, EnOcean Link can be run as
a web service in the cloud. Here, an EnOcean gateway and the according
application are combined onto a separate hardware. Smart nodes, such as
batteryless sensors and actuators, provide their information to the
gateway that forwards a request to the EnOcean Link web service via the
Internet to interpret the received telegrams. The middleware extracts
the value and data and sends them back to the gateway/application
hardware for further processing. That way, the major part of the
EnOcean-specific data processing is executed by the middleware in the
cloud. Therefore, the gateways itself don’t need to cover a high
computing power and can simply focus on the application.
The actual data interpretation service runs on an external server
outside the building and can be offered as service on demand. In a
scenario of a wider building automation system, several gateways and
applications can access the same EnOcean Link web service. This enables
system planers to easy and flexible build up complex networks on the
basis of simple and cost-effective gateways.
Test web service
Particularly for OEMs who intend to set up their own cloud service
based on EnOcean Link middleware, EnOcean offers a test web service
that can be used through a website or from an application. The service
acts like EnOcean Link via HTTP requests and demonstrates the
functionality of the middleware in the cloud. It is useful for smaller
demonstrators or as a starting point for an own web service
development. Its main purpose is to demonstrate the potential of
EnOcean Link and its use in the cloud.
The web service
can analyze, for example, ESP3 telegrams supplied by a
sensor and return the complete parsed telegram structure (e.g. RORG,
DATA, Source ID etc). If the forwarded telegram is a teach-in telegram,
the web service stores the ID and EEP for further processing. If this
data is not used in a specific period of time, the information in the
database is deleted. If a telegram is being forwarded using a known ID
and EEP, the web service interprets the given telegram according to the
chosen profile and provides the included channels as described before.
The interpreted data are returned afterwards. Further details on the
usage of the test service and steps how to build up an own cloud
service based on EnOcean Link middleware can be found in the
application note “Combining EnOcean Link with a web
One middleware – multiple use cases
Using EnOcean Link as a cloud service is just one example that shows
the possibilities of the middleware for flexible automation scenarios.
As the middleware works independently of a specific frequency, it can
be integrated into any gateway, regardless of the communication
standard it uses. Due to its embedded architecture, EnOcean Link can
even be run on a mobile device, bringing the intelligence to the
smartphone, for example. Thus, OEMs can develop apps based on the
As the middleware transforms energy harvesting wireless communication
to any other standard protocol, it consequently opens up various fields
of application even outside buildings. In such scenarios, self-powered
sensors can monitor the structural health of bridges or send an alarm
signal when they measure the heat of a forest fire as part of an early
warning system. Finally, EnOcean Link lays the foundation of an
Internet of Things where billions of batteryless devices are connected
to each other and the Internet. Having said that, the middleware offers
OEMs a future-proof approach as it is updated continuously to cover
even next generation energy harvesting wireless solutions.
About the Author
Hönsch is Product Manager and Software Architect at EnOcean. In this
position, he is responsible for EnOcean software products and security
concept, including the development of EnOcean Link middleware. Marian
holds a bachelor in Informatics and a Master of Science magna cum laude
in Software Engineering.
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