Our last research project was real fun: Build a Webcam with temp and light sensor to do some home/office automation.

We took a RaspberryPi model B, temp sensor (DS18B20) and light sensor (TSL45315).

The temp sensor had a 1-wire interface and the Internet had many tutorials to connect the sensor to a RasPi. It should be a trivial job, if you read the tutorials and it should be ready in max. 10 minutes. Should!

The theory wasn't the reality and the tutorials didn't cover our environment, because we had a new Raspbian ISO with kernel 3.16 and 3.18 some hours later.

We tried to connect the sensor as described (with and without pullup resistor, with parasite power and without) but it wasn't detected. It was horrible because the driver was loaded without problems and logged a simple success message.
We didn't find information about the problem because we didn't see an error. It simply did nothing and the filesystem didn't contain the relevant files and directories. Our /sys/bus/w1/devices directory was clean and empty. After some hours error searching, without any ideas we tried an older Raspbian image with kernel 3.6 and our sensor worked out-of-the-box without modifications. We saw additional log information from the 1-wire module which we didn't have with our 3.18 kernel. So we knew that something has changed in the kernel or kernel config...

But we weren't happy because the whole thing should work with an up-to-date setup. After we knew that the kernel caused our problems, we tried to find a solution and found: http://www.raspberrypi.org/forums/viewtopic.php?t=97216&p=676793 (first posting on 2nd page). There was a hint about the device tree. With this information, we found: https://github.com/raspberrypi/documentation/blob/master/configuration/device-tree.md

We disabled the device-tree by adding device_tree= to our config.txt and everything worked after a reboot, with our 3.18 kernel. So far so good.

It also worked with device_tree_overlay=overlays/w1-gpio-overlay.dtb. This option was our preferred one because it didn't disable the device_tree.

After our temp sensor worked without problems we connected the Raspicam and made some tests. Everything worked without problems. The last piece of our project was the light sensor. It was a littly bit tricky to use the sensor with our Pi because the source code example wasn't available for Java/Pi4J, but here it is:

We compared the output with an Arduino board and the values were "the same".

It wasn't possible to use the light sensor without required modules. We simply added device_tree_param=i2c1=on to our config.txt and I2C worked. You should install

to verify connected sensors, via:

After we thought that everything will work, we put all pieces together: temp sensor, cam, light sensor.
During development, we didn't use all parts together - only the relevant sensor, to rule out errors.

Everything worked fine after starting the Pi, but the cam stopped capturing after some minutes... frustrating.
So again we tried to find an error without detailed information and without logs. We thought it might be a module loading problem and found some hints: https://github.com/raspberrypi/linux/issues/435. But nothing worked for us. The only working solution was: disable the device tree

The whole system is up and running for some days and there we no problems.

We currently don't know what's the problem with the device tree or what we should configure to avoid problems, but if you have similar problems, this posting could help. If you have a working solution with the device tree... leave a comment

I wrote in a previous article about my problems with Jetty and Vaadin push support.

I found the problem in the meantime and Jetty works well on my Raspi. The performance is a little bit better than with Tomcat 8.

What was the problem?

Vaadin 7.1 push implementation was incompatible with Jetty 9.2.6. I had to use Jetty 9.0.7.

I didn't use Jetty as embedded server, it runs standalone via bin/jetty.sh. It was a little bit tricky to add an external lib to the classpatch because the commandline argument changed from 9.0 to 9.2.

I had to add following to my jetty.sh:

With 9.2:

You have to know the pitfalls

It seems that Vaadin' websocket implementation for Jetty is better than for Tomcat because Vaadin handles multiple rotate/resize events faster with less communication. I know that Vaadin 7.3 has a better websocket implementation and it's also up-to-date and should work with Jetty 9.2.6, but I still use Vaadin 7.1.

I recommend Jetty for your embedded project because it's fast and simple. If you prefer Tomcat, you can't do anything wrong.

Oh... I also solved the problem with missing request from / to /index.html. The redirection won't work if you don't have a file with the name index.html in your public web area because Jetty does nothing in that case. I didn't find an option for that, but creating an empty index.html solved my problem because I had a Servlet which was listening on /index.html.

It's not rocket science and we didn't write code, but it's nice to see our UIs on SmartTVs

Here are some impressions:

SmartTV - Statistic		SmartTV - Data
SmartTV - Window Shutter

Because I got some emails, here's the window shutter UI how it looks on my Wii U. Sure, the space is not perfectly used, but the UI wasn't optimized for Wii U. Also the agent name of the browser wasn't checked to optimize controls.

But it's ok and control just works

The pictures (phone cam):

Wii-U controller

Wii-U (TV)

It's about two years ago that I wrote about controlling window shutters. The system run for 2 years without problems but it was time to change "something" because it was vacation time and I thought it would be useful to showcase our vaadin UI

The old system was controled via (good old) SMS - without GUI. It had a lot of commands but only en/disable up/down were heavily used because the integrated public holiday and weekend automatism solved most use cases. The SMS contol was great and worked without problems but it was a problem if you didn't know the commands and syntax by heart!

Another consideration was a simple real-world showcase for our vaadin UI, the responsive feature and push support. Our application frame was already responsive and worked on desktop, tablet and smartphone browsers. I thought about using AngularJS or different "hypeware" but I didn't have weeks to research and implement. My new GUI had to be finished in few hours. And it should be maintainable for the next two (or more) years without problems.

I love researching hypeware... but simply read some articles if you want:

• 10 Amazing Libraries for Your Web-based JavaScript Applications
• 7 Exceptional JavaScript Frameworks for Mobile App Developers
• Generation Javascript

There are too many frameworks, everyone is different - no real standard APIs (didn't count HTML and CSS). You can't be sure that the framework is future-proof because developers love to change software to be incompatible with previous versions just to be state-of-the-art.
And why should a developer use 5 or more frameworks to create a simple application for desktop and mobile? You'll need more libs if your application needs DB and CRUD support.
C'mon we need simple and small frameworks and not what we have right now! The world is talking about microservices and what about "micro frameworks"?

Conclusio: I didn't find something comparable to JVx. Of course, it's my opinion and I'm JVx developer, but I'm a researcher and the technology isn't a problem if it makes sense to use it.

To be honest: Our Vaadin UI in combination with other JVx features is unbeatable for most application types. Of course, it's not recommended for web pages with custom layout requirements. If you need an "application style" solution with menu and screen/work area or form based - there's nothing comparable.

After I knew that my new GUI would be a JVx' vaadin solution, I had to think about the details. The whole application should be responsive to support every modern device and desktop browsers as well. The application server should be Jetty or Tomcat and it should run on the RasPi. The performance is not critical because the hardware is limited (but cheap).

Software stack: clear
Hardware: clear
Deployment type: clear

Next step was development. This was easy because I re-used existing classes and added some get/set methods to access internal members. The most important change was an event listener because every vaadin client should be updated immediate via push. It wasn't possible without notification mechanism. I thought about an event bus and played around with mbassador. It's a nice and small lib, fast and just works (recommendable).
To be honest: I didn't need it because I didn't need more than one listener and an event bus is not much more than a listener abstraction (with some extras).

After some hours developing and refactoring, everything was ready for a test.... The next decission: Jetty or Tomcat?
I worked with Tomcat for many years and didn't know much about Jetty, only that it's the number one for embedding into applications, supports SPDY and has websocket support. I played around with Jetty and got it running. The installation of my GUI worked like a charme and everything worked except push. I found solutions for embedded run mode but not for standalone Jetty. I'm pretty sure that I missed something, but I wasn't very patient and switched to Tomcat 8.
Not only because of my push problem but Jetty didn't handle requests as expected:

http://localhost/house/ didn't redirect to http://localhost/house/index.html automatically. I didn't have an index.html file in the public file area, anyway the request should be executed. Such requests work with Tomcat without additional configuration.

I'm not happy that my Jetty server didn't work but I'll retry it in the next days

Here's a simple screencast of my solution because it's easier to understand:

It took me less than one day to finish my GUI and the best: It's family safe.
I tried the GUI with PS4 and WiiU integrated browser and it was great to see shutters moving.

Summary

I've used a RaspberryPi, installed Tomcat 8 with Java8 and deployed my application as war file. The GUI is responsive and supports push via websockets and runs on every device in my house. It wasn't planned using gaming consoles

Oh, I forgot to mention: During my tests I found out that Android and iOS support custom Bookmark images for Desktop links but this needs additional tags in index.html (works without, but it's better to include the tags). Our VaadinUI now has built-in support for such images

The switch component is available in the Vaadin Directory.

My latest article about cross platform GUI development is available in current edition of Java aktuell. It's a German magazine and the article is in German!

It's all about application development for Desktop, Web and Mobile (native or web). It's based on Single sourcing and JVx.

You can read the article here (if German isn't a problem). Feel free to post your Feedback!

There's a nice AddOn in the Vaadin Directory. It's a switch button/checkbox. There's an older version for vaadin 6.6+ and the current version for 7.2+.

But the 7.2+ version is not compatible with vaadin 7.1+. We checked the source code and made a version for 7.1.

If you need a 7.1 compatible switch AddOn, simply use this archive. It's a zip archive which contains the pre-compiled class files and changed source files. Simply use the zip (or rename it to jar) to rebuild your widgetset.

Don't use the 7.1 version for 7.2 because the API is different and it won't work. Simply use the original version for 7.2 and newer.

Plain JVx Vaadin applications don't have page navigation as known from e.g. JSF applications. If you press "back" in your browser, the whole application is lost and "forward" will create a new application. Same problem with "reload".

It has nothing to to with JVx because it's a technology restriction. Isn't it?
Not necessarily!

You should know that vaadin has support for Browser Navigation, but this feature has no standard implementation because every application is different and has different requirements. If you create your own Vaadin application, you'll have to implement your own Navigation. It's not tricky but you should know how it works. A good starting point can be found in the book of vaadin. The main thing is that you should create your application with different views. A view is more or less a page. The navigator supports navigation between views. If you have different views, it's easy to use the Navigator.

But our generic application is a little bit different to plain Vaadin applications because JVx has work-screens. A work-screen is like a View or a page, but technology independent. A work-screen can be used for desktop applications and web applications without code changes. A desktop application usually doesn't offer Navigation as known from web browsers. So it's a good idea to have work-screens because it's independent of the used GUI technology and platform features.

If you use a JVx application as web application with Vaadin UI, you'll miss page navigation - for sure. We made some experiments with vaadin' page Navigation and are happy to present an awesome solution for this problem.

We did a generic implementation in our application frame and now it's possible to navigate between work-screens - out-of-the-box. It's implemented once in our application frame. Simply use it and page navigation works!

Here's a short demonstration:

We have a great new feature in our generic web application. It's now responsive and supports big and small devices like smartphones, without additional coding. Everything will work out-of-the-box.

The application is generic which means that it's an application frame that can be used for you own requirements. We have a simple demo application for our internal tests.

Have a look:

The menu changes the position and size. Also padding and margin are different if there's not enough space.

Merry X-mas

We have a little present for you. It's a connector for Dropbox.

The source code is available here.

It's a full IStorage implementation and allows CRUD operations to your Dropbox account. We use it for sharing dynamicly created reports and as document archive. It's very useful because your application doesn't need a mobile client to exchange data with the backend.

If your secretary creates the management report (Word, Excel or Pdf), simply modify or read it via Dropbox. It's really simple because Word and Excel are available for mobile devices. Both tools have a built-in Dropbox support and thus makes it easy to access files.

How to use the storage?

Currently, we don't have a pre-compiled lib, but simply clone the repository and use the ANT build to create your own lib.

It's simple to integrate the storage in your application:

Before the storage will work, prepare your dropbox account to get an access token. It's not tricky and everything is documented.

There are some examples available as JUnit tests.

A simple Dropbox screen could look like this one:

Dropbox access with JVx