I have an Android app (not written in Qt) and a Linux application (written in Qt). They shall communicate via NFC with each other. The Linux box has an ACR122 smart card reader.
My plan is to use the Linux side as the initiator and the Android app as the target of the NFC communication. Moreover, I plan to use the peer-to-peer mode of NFC in the passive variant. I.e. the Linux box actively powers the HF field all the time, NFCIP-1 is used on the transport layer, on top of that LLCP and finally NDEF messages are exchanged.
If I understand the specs correctly, the initiator dictates the operation mode (424 kb/s, p2p-mode, passive). But I do not find any way how to set the operation mode through the Qt library.
What am I missing?
Some more background info
My initial idea was to (only) use libnfc for the Linux application as the application is only a CLI daemon and so Qt is actually not a real requirement. However, then I found out that libnfc is really low level. It does not provide an interface for the LLCP level nor NDEF data structures. I also found libllcp from nfc-tools and libndef (which is based on Qt core) but both seem to lack any documentation. Finally, I ended up with the idea to use Qt for the Linux application.
Related
I try to developing simple scada system with C++ in Qt. I want to control hardware or get status(or something) of hardware and send to server or router.(actually my application control softwares too)
And in finish: Qt have a good tools for scada systems?
As of QT 5.7 there is a new Serial Bus library for use with protocols such as CAN BUS and MODBUS, you can read more about it here:
http://doc.qt.io/qt-5/qtserialbus-index.html
For your scenario, QT has plenty of Network support that you could use for your interface, depending on what your hardware specification is. QT does not compare to 'out of the box' SCADA solutions such as a Siemens SCADA system, however developing one based on QT could give you much more flexibility. Depending on what you are trying to achieve, this becomes a trade-off between productivity/time to market and flexibility/value add.
Also there is an opensource qt scada toolkit https://github.com/IndeemaSoftware/QSimpleScada, for visualization.
I am developing an application on Windows 10 that interacts with custom device drivers, the NTFS filesystem and DirectX 12. The app is a Windows Universal App written in C++, WRL, XAML and DirectX. For DirectX I have chosen a SwapChainPanel control and the DirectX portion of the app works great. The app is Sideloaded so I have a bit more freedom than an app that needs to go through the store
Unfortunately the Windows Universal Apps have a number of restrictions with regards to API calls. WinRt APIs are favored.
Here are a list of WinRt APIs to call to replace Win32 APIs:
https://msdn.microsoft.com/en-us/library/windows/apps/hh464945.aspx
In addition Windows Universal Apps can call Win32 APIs that are partitioned to the application (however not the ones partitioned to the desktop) as indicated in the documentation of each function and in the header file. Here is a link:
https://msdn.microsoft.com/en-us/library/windows/apps/br205762.aspx
In addition the Winsock APIs are now allowed from Windows Universal Apps
However I am still left without my favorite (and necessary APIs)
CreateFile()
ReadFile()
WriteFile()
DeviceIoControl()
CloseHandle()
In particular I need to read and write files to all locations without user interaction (and not to the locations restrict by the Windows Universal App Sandbox). In addition I need to send IOCTLs to my multiple device drivers.
I could abandon Windows Universal Apps and go with WPF. However I have a touch intensive application and I need touch to work really well. In addition I have to wonder about the lack of fixes and commitment to WPF on the behalf of Microsoft. I have considered other UI frameworks but none have been as promising as a Windows Universal App.
Microsoft has allowed two paths in Windows 10 for Universal Apps that will allow calling all Win32 functions (For side loaded apps).
Brokered Windows Runtime Component
and IPC though TCPIP
I have written a brokered windows runtime component and it works well. However the solution requires a C# app to be in the mix and I do not need/want that as I need fast load times of the app and do not want to pull the CLR in.
The next option is IPC through TCPIP. I would use Fast TCP Loopback as explained in the blog post: Fast TCP Loopback Performance and Low Latency with Windows Server 2012 TCP Loopback Fast Path. I would link to it but I am at my (very generous) two link limit for a first post.
I have a couple of questions:
1) If I go this route should I place the IPC between the XAML controls/buttons and the rest of the App? This would allow the rest of the app to be strictly Win32. Or should I just place the IPC between the app and calls to the specific functions I need that fall outside of the those allowed by Win32.
2) I have looked for a library or paper that has code and/or ideas for implementing IPC with TCPIP. However so far the papers that talk about IPC with TCPIP seem to simply describe winsock programming which is something I already know how to do. I would enjoy coding up IPC but would prefer a solution that has been tested. This needs to work flawlessly and I would rather have code with some time on it. Has anyone used or heard of code and or a design for IPC over TCPIP that is available to share?
I am writing an application using Qt and want to try and deploy it as a web-application. I want user's to be able to use my application by accessing it through a web browser. I'm guessing that's what a web-application is? What kind of options do I have? I've never looked into doing anything like this but I'd like to learn something new.
EDIT: What if I deployed my application on a Linux server and had users access/run it through a terminal? I think writing web application is going to be more complicated than I had originally thought.
If all you have is a Qt application, then the best you can do is use Qt 5 and run it using a remote visualization package:
Use WebGL streaming, introduced in Qt 5.10. Qt exposes a browser-connectible interface directly, without need for third-party code.
For Qt 5.0-5.9, you can use the vnc platform plugin. Then connect using a web-browser based vnc client.
For many uses it might be sufficient, and certainly it's much less effort than coding up a web app.
You're looking for Wt which provides a different set of drawing routines for many Qt GUI elements, turning them from lines on screen to HTML controls.
http://www.webtoolkit.eu/wt
It also handles websocket calls to provide interactivity. It seems a great idea, let us know how it works in practice.
For the case of QML there is QmlWeb which is a JavaScript library that is able to parse QML-code and create a website out of it using normal HTML/DOM elements and absolute positions within CSS, translating the QML properties into CSS properties.
QmlWeb is a small project by Lauri Paimen that he’s already developing for a few years now. QmlWeb of course doesn’t yet support everything Qt’s implementation of QML does, but it already supports a quite usable subset of it. It supports nearly all of the most basic QML syntax. Moreover it has support for HTML input elements (Button, TextInput, TextArea are currently supported, more to come).
Well, QmlWeb is not finished. I hope Digia help with this project to make it ready with mature features.
Interestingly, it is possible to compile Qt applications to javascript using emscripten-qt. These run fairly fast with Firefox's asm.js interpreter:
http://vps2.etotheipiplusone.com:30176/redmine/projects/emscripten-qt/wiki
Try "Qt for Webassembly".
Webassembly allows the C/C++ code to be compiled and run natively inside majority of the browsers:
WebAssembly (Wasm, WA) is a web standard that defines a binary format and a corresponding assembly-like text format for executable code in Web pages. ... It is executed in a sandbox in the web browser after a verification step. Programs can be compiled from high-level languages into Wasm modules and loaded as libraries from within JavaScript applets ... Its initial aim is to support compilation from C and C++, though support for other source languages such as Rust and .NET languages is also emerging.
To run a Qt application unchanged over the web so users can operate it in a browser, you can compile it for Android using the x86 Android ABI, run it inside an Android emulator on a server and supply the Android Cast videostream to users' browsers. You'll also need to have JavaScript in place that records the keyboard and mouse events on the web clients and relays them back to the server.
I had previously tried Qt WebGL streaming and found it to be good over the local network but too slow over the Internet. A 10 s application startup time is acceptable, but 3 s to show a new screen is rather not. I had the exact same experience with the Qt VNC platform plugin. Compared with that, the Android Cast streaming based appetize.io solution (see below) was much faster, providing a well usable user experience even over my 8 Mbit/s connection.
Existing solutions
Here is an overview of commercial products and open source software components that I found that can help you with this approach:
appetize.io. This is a commercial product to run Android applications over the web for demo and testing purposes. I have just done this with a Qt QML based application and liked the outcome. When choosing an Android 9 / 10 device you can see that the "Screencast" setting is on; which is why I believe that this solution uses the Android Cast technology.
runthatapp.com. This is another commercial offer. Not as sophisticated (yet) as appetize.io, but providing a nice pay-as-you-go scheme.
ScreenStream. An open source Android app that provides a web server to view the screen of one Android device in a web browser, also relying on the Android Cast technology. That Android device could be an emulator running on a web server. And to make this multi-user capable you can employ a small load balancer similar to a technique that I developed for Qt WebGL streaming. The ScreenStream README shows that the application might consume up to 20 Mbit/s per client in short bursts.
Ideas for future improvements
Serving your Qt app as an interactive live video stream seems a promising idea to me, given that I found it already less sluggish than VNC and similar solutions. There are ways to make this even faster, such as using a hardware H.265 video encoder to create a video stream with very little delay. By operating multiple such encoders on a single server, the server could serve multiple clients and still keep its CPU load low. Maybe there are even better video formats for such a purpose, given that user interfaces of programs lend themselves well to lossless compression.
Some hints for appetize.io
Finally: since I used the appetize.io product for a Qt application over the last few days, here are some tips from that experience:
It is necessary to compile your Qt application for the x86 Android ABI. The default armeabi-v7a ABI will not work because most appetize.io devices are actually server-based Android emulators and the only ARM based device ("Nexus 5 Physical") failed to start any Qt application I tried to use with it.
The x86_64 ABI may also work, but you might then have to also compile Qt yourself for it, as not all versions of Qt come pre-compiled for that architecture.
All appetize.io links (both for standalone pages and embeddable iframes) support GET parameters to configure the app presentation format. Especially relevant here is screenOnly=true to show the app without a picture of a phone or tablet around it.
Features that rely on phone hardware (camera, position etc.) will not work or only show dummy data. But if you really wanted, you could create a hybrid application combined with client-side JavaScript. It would run device-dependent code in the user's browser, for example to take a photo with the webcam, and then provide the results to the Qt application via the appetize.io cross-document messaging protocol. The following message types seem suitable to build a simple communication protocol: pasteText(value), keypress(key, shiftKey) and openUrl(value).
In the default appetize.io standalone app demo pages, only the key events of ordinary letter keys are sent to the app, not keyboard shortcuts or function keys like F2 and Esc. This might be possible to fix with JavaScript on an own page embedding the appetize.io iframe, as their cross-document messaging protocol provides the keypress(key, shiftKey) message type.
Qt does not support writing browser based web applications. Unfortunately.
You need to use common web programming technologies for this. There are a lot of ways, but Qt is not one of them.
I wanted to know if there is any stack independent C/C++ bluetooth api for windows (XP, Vista, 7, x86 and x64).
My target is to create a connection and send/receive some time critical data over bluetooth.
My researches gave me the following options and there disadvantage for this task:
Windows Sockets for BluetoothOnly works with microsoft bluetooth stack
Using the COM port (CreateFile/ReadFile/...)Slower than the socket option and the user has to connect to the device first.
Use stack dependent APIThis would require to detect the used stack and create read/write functions for every stack. Very time consuming and I don't know if it is even possible to support all stacks
Writing a KMDF driverI thought about writing a function driver to talk directly with the bluetooth HCI driver which should be stack independent. This would be very time consuming because I would have to read the whole bluetooth spec, or is there an API for the HCI commands?
I know that there is also a commercial sdk from btframework.com which supports most (or all) bluetooth stacks, but I need a freeware option.
Please tell me if there are any other options for this task.
If there aren't any, could you tell me which options you would prefer and why?
Is it okay to use Windows Sockets and ignore the other bluetooth stacks?
Thanks for your help :)
I guess one option would be to use C++/CLI to interface with my managed Bluetooth library 32feet.NET which supports most of the stacks on Windows. http://32feet.codeplex.com/
I've been successfully using this library it is called WCL but it is not free. With this you can connect through SPP without requiring to create a virtual COM port.
While their documentation is not very good, they provide some good demo code that you may want to try.
It supports the Microsoft, Toshiba, Widcomm and Bluesoleil stacks and there is a native C++ implementation (as well as a .NET one).
The library should;
Be easy to use and few lines of client code should accomplish much
Be as platform independent as possible. (In case of future ports to other platforms)
Have C++ bindings.
Be mature and stable
I would also like to be notified of most HID events through callbacks.
I have considered the following alternatives:
libhid - (Unfortunately?) this is GPL and cannot be used in my application.
WDK - Seems to be a bit low-level for my use. I don’t need that kind of control.
atusbhid - This has an appropriate level of abstraction, but it is firmly tied to the Windows messaging loop
Are there other alternatives to offer?
Take a look at hidapi: it is C, which answers the C++ bindings question (effectively :)), is cross platform and has a very permissive license.
It doesn't appear to have the callbacks, but...
If libhid works for you, then perhaps the thing to do would be to write an application (which you would GPL), which uses libhid to talk to devices, then provides whatever you need via a TCP connection. Your real application would connect via TCP to do what it needs. This would obviously be a massive performance hit.
This application would effectively be a 'shim' between libhid and your application. In this case, the shim would exist for legal, not technical, reasons.
I'm not saying it's a good idea, just that it's an idea.
Consider rolling your own. You'll have total control over the interface, the level of platform independence, and such. Even though a project is GPL, you can use it as a recipe for your own, and as a testbed to find issues with your own.
There are several USB HID host drivers for Windows. An easy-to-use dynamic-link library is from http://embedded24.net.
There are also several example applications included for Visual Studio 2010 (C++, C#, and Visual Basic).
HIDmaker software suite from Trace systems is an option.
Pros:
Easy to use (excellent for learning how to program for USB HID)
Generates working applications source code in a various project formats (Visual Studio and Borland)
Generates stable example code for both host and device (stable in my experience)
High performance (if HID can even be said to have high performance in the first place)
Cons:
Only works on Microsoft Windows
Uses its own USB library I think (ActiveX)
Look at this code:
Read and use FM radio (or any other USB HID device) from C#
It gives you some simple classes to talk to a HID device. It boils down to getting the alias for the device (something like \?\HID#Vid_nnnn&Pid_nnn#...) and use CreateFile to open it. You can get the device's alias under HKML\SYSTEM\CCS\Control\DeviceClasses\{4d1e55...}\.
The Vid and Pid are the vendor ID and product ID of the device (check Device Manager).