The introduction of Windows 10 IoT running on the Raspberry PI enabled the Windows platform for the implementation of all kind of interesting applications using the familiar development environments such as Visual Studio and C#. Now with the release of .NET Core 2.2, the Windows IoT platform supports web application development out of the box requiring no custom solutions (e.g. web server running as a background application).
A typical scenario for a Raspberry PI based application is home automation. Besides typical monitoring applications with a variety of sensors, the integration of different devices such as ventilation units, power meters, PV inverters, heating boilers, Z-Wave controls become an important issue.
The various devices provide a wide set of application and user interfaces ranging from web interfaces, REST based web API's to industrial Modbus TCP. Some of the systems provide remote access to cloud based services requiring different security support (two phase login, OAuth, custom secrets, passwords etc.).
The home control web application should provide a web interface for selected data, the integration to cloud based monitoring services such as ThingSpeak, and a consolidated REST based web API to simplify data access. The Home Control Web Application gathers data from a various sources using REST based Web API's or Modbus TCP:
- ETA PU 11 Pellets Boiler
- b-Control EM300-LR energy manager
- BMW Wallbox Connect
- Helios KWL EC 200 Ventilation Unit
- Fronius Symo Inverter
- Netatmo Weather Station and Modules
- Zipato Zipatile Z-Wave Home Control Unit
- Windows 10 IoT Core
- ASP.NET Core 2.2
- Serilog Logging Framework
- Modbus TCP (NModbus Library)
- Swagger (Swashbuckle.AspNetCore)
- Syncfusion (UI Controls)
Windows IoT Core is a version of Windows 10 that is optimized for smaller devices with or without a display that run on both ARM and x86/x64 devices.
With ASP.NET Core 2.2 the promise of cross platform development of various application types (console applications, web applications etc.) become even simpler. As it has been shown before, the deployment of ASP.NET web applications to a Raspberry PI running Windows 10 IoT is pretty easy
- just compile the web application for the win-arm run-time platform
- and publish all to a directory on the Raspberry PI.
Serilog logging for ASP.NET Core is available with the Serilog.AspNetCore package. This package routes ASP.NET Core log messages through Serilog, combining information about ASP.NET's internal operations logged to the same Serilog sinks as your application events.
NModbus is a C# implementation of the Modbus protocol and provides connectivity to Modbus slave compatible devices and applications. It supports serial ASCII, serial RTU, TCP, and UDP protocols.
Swashbuckle.AspNetCore is a Swagger tooling for API's built with ASP.NET Core. It allows to generate API documentation, including a UI to explore and test operations, directly from your routes, controllers and models.
In addition to its Swagger generator, Swashbuckle also provides an embedded version of the wellkown swagger-ui that's powered by the generated Swagger JSON.
Syncfusion's Essential Studio Enterprise Edition is a suite of components and frameworks for developing web, mobile, and desktop applications. Eligible developers and small businesses have free access to Syncfusion's components, controls and frameworks for web, mobile, and desktop development.
The access to the various devices is implemented in custom libraries targeting the .NET Standard 2.0. This allows the use of the libraries in different applications (console application, Windows Universal application, ASP.NET Web application). All the internal specifics of the data access is hidden, exposing only the various data properties and read and (optional) write operations.
- ETAPU11
- KWLEC200
- BControl
- EM300LR
- Fronius
- SYMO823M
- Netatmo
- Zipato
- NModbus
- DataValue
- BaseClass
- HomeControl (UWP)
- HomeMonitor (Xamarin)
Typically for a particular device a .NET Standard 2.0 library is created, providing all necessary communication and data fields to support the device. A console application is provided to allow read and write operations (if the device supports write access) for testing and convenience. A Web application providing simple monitoring, a REST based API and a SignalR based monitoring hub for all the device data. A test project based on XUnit is used to test the various applications and libraries.
Every device project has typically four projects:
- DeviceApp (a .NET Core 2.2 console application)
- DeviceWeb (an ASP.NET Core 2.2 web application)
- DeviceLib (the .NET Standard 2.0 device library)
- DeviceTest (a XUnit test application)
Some device project contains a simulation (console) application to simplify testing. The Windows 10 UWP app uses the various Web applications to provide a simple common user interface. The Xamarin based monitoring app is an example of a mobile application running on Android phones.
The console application uses several utilities to provide a simple to use application framweork:
- CommandLine.Core.CommandLineUtils
- CommandLine.Core.Hosting
- Microsoft.AspNetCore
- Microsoft.Extensions.Configuration.Json
- Microsoft.Extensions.Configuration.EnvironmentVariables
- Newtonsoft.Json
- Serilog
The console application implements the Program class (providing the main entry point) and the Startup class implementing configuration and logging. The device specific singleton instance (using a Modbus or HTTP client) is created. The various commands (root, read, info, monitor etc.) implement the actual device operations provided by the device library.
All console applications are using a JSON configuration file containing common application settings ("appsettings.json").
The various devices have very different interfaces ranging from custom web services to Modbus TCP.
| Device / Service | Interface |
|---|---|
| ETA PU 11 Pellet Boiler | Modbus TCP, REST Web Service (local) |
| Helios KWL EC 200 ventilation unit | Modbus TCP |
| b-control EM300 LR energy manager | Modbus TCP, REST Web Service (local) |
| Fronius Symo 8-2-3M | Modbus TCP, REST Web Service (local) |
| Netatmo Weather station | REST Web Service (remote) |
| Zipato Zipatile | REST Web Service (remote, local) |
The various REST web services also have different authentication requirements. All the access methods and the various data values are handled in their respective .NET Standard 2.0 libraries.
The device library implements read (and optional write) operation for the observed device data values. Depending on the device communication the library hides the actual protocol implementation. The use of Modbus is simplified by using a Modbus TCP client (provided by a custom NModbus extension library). In case of a device specific web service, the HTTP communication is provided by a HTTPClient instance. The device specific rest web api's and associated security implementation (username, password, usersecrets etc.) simplifies the data access.
The constructor of the device class provided by the device library uses a logger, a client instance (Modbus or HTTP client), and device specific settings data. The cached device data hold the device specific data values as properties. The device data typically are derived from the DataValue helper class and implement the IPropertyHelper interface.
The web application uses the device specific library to implement a consolidated REST based web api for access to the (cached or updated) device data values. The cached device data values are typically updated every minute utilizing a background timer task. The updated data values are also provided by a SingalR based serivce propagating the update events. The web application also provides a common web site with access to the data values (updated using SignalR) and a Swagger based web api test interface.
The XUnit based test project typically implements tests for the device specific library, the web application, and the console application.
The BaseClass library provides a set of helper classes to facilitate the implementation of applications by providing standardized implementations in various contexts. An application class is derived from the corresponding base class using the default implementation (constructor, properties, methods).
In order to facilitate the access to the actual monitored (or controlled) data, property set and get routines are added to allow a dot-notation for properties supporting nested classes and simple arrays and lists.
The devices providing a Modbus TCP interface are integrated using the NModbus Library with several extensions for additional datatypes such as strings, floats and double. The Modbus TCP protocol is used only on the internal network and is not exposed to the outside. This is also used for additional tools such as a gerneric command line Modbus application or an Modbus TCP gateway providing a REST based interface via HTTPS.
The standard ASP.NET web application template using razor pages. Several pages are added to display selected data from the various components. For a more graphical overview the Syncfusion components are used to display circular gauges. An additional page is used to embed the Swagger Web API.
The SignalR communication framework in ASP.NET Core 2.2 is used for propagating updated data values. It is used to allow the monitored data values to be updated and displayed on the associated web pages automatically in the background.
Simple singleton services provide the access to the instances for the actual devices. The monitor services running in the background implement the automatic update of monitored data typically every minute, accessing the devices (Modbus TCP, Web API's etc.) and synchronizing the local cached data instances.
The monitored data from the various devices are also made available via set of consolidated REST based web API's. Swagger integration provided by the Swashbuckle project adds Swagger to the WebApi project providing a rich discovery, documentation and playground experience to the REST API consumers.
In order to simplify the access to the monitor and control values a consistent set of REST based web services are implemented. The typical REST interface is comprised of a simple set of functions:
GET /api/{device}/all - Returns all device data.
GET /api/{device}/overview - Returns a subset of the device data.
GET /api/{device}/property/{name} - Returns a single device property.
PUT /api/{device}/property/{name}?value={value} - Writes a single device property.
The varios subsets provided by the REST interface (and the underlying library) are used to prevent to update all data values (could be rather slow, depending on the device interface). Note that only the ETAPU11, the KWLEC200, and the Zipato device support write operations.
A Web application can be deployed on the various platforms supported by the ASP.NET Core 2.2 framework. It also runs on a Raspberry PI 3 or Raspberry PI 2 B using Windows 10 IoT Core by simply publishing to a directory on the Raspberry PI.
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