Customising KWeb?

[Magimedia]

I want to interface a web page on the Pi with some hardware on the GPIO (mainly buttons and a couple of LEDs. I'm not sure of the best way to do this. I wondered if a plugin could be written for KWeb, or even customised and recompiled. What is the best way to approach this requirement?

[gkreidl]

It depends on the complexity of your project.

Action being issued from the web page are simple as kweb supports any kind of command, script, program with special links, buttons or forms.

Listening to events (button pressed) is not so easy but can be done for simple things, if you control kweb remotely from a script using xdotool. An easy way might be sending user definable keyboard commands (ALT+0 ... ALT+9I) to load special pages which in turn can execute commands etc.

Check the kweb manual for details and examples.

For more complex stuff you need a web server with kweb as front end.

[Magimedia]

In terms of what would be most useful, would be the ability to read from, or write to, the GPIO pins from a Javascript library. Manipulating the stuff in Javascript is no problem once it's in, but interfacing with it is the issue. Is there anything in kweb that can do this, or plans to add it?

[gkreidl]

In terms of what would be most useful, would be the ability to read from, or write to, the GPIO pins from a Javascript library. Manipulating the stuff in Javascript is no problem once it's in, but interfacing with it is the issue. Is there anything in kweb that can do this, or plans to add it?

No. That would require interfacing to the DOM and the Javascript library which would make the browser ten times more complex that it is now.

[Magimedia]

That's what I thought, hence wondering about a plugin. If I could write something in Python to do the main leg work, and then expose function calls to KWeb, it would make it infinitely expandable. It would seem a sensible feature for K Web too, since a kiosk could then be any customised display unit, including POS built to spec.

[gkreidl]

That's what I thought, hence wondering about a plugin. If I could write something in Python to do the main leg work, and then expose function calls to KWeb, it would make it infinitely expandable. It would seem a sensible feature for K Web too, since a kiosk could then be any customised display unit, including POS built to spec.

kweb already has a kind of plugin-interface (using Python scripts) and this is much more than any other browser supports, but that is only in one direction. Limited control from the outside is possible via xdotool.

For everything more complex, use a web server approach and some real time connection using AJAX calls.

[Magimedia]

So I need to learn how to setup websockets using Tornado or similar? As far as I know, using AJAX for browser-instigated stuff is fine, but it doesn't support push, so I'd have to use up a lot of CPU time repeatedly polling with AJAX calls, which would expect to eat a lot of CPU.

Any better methods than this, or is it time to sit down and start learning?

[Magimedia]

Node.js ?

[ghans]

It doesn't really matter what server , framework ,
framework + server or framework-with-integrated-server
you use. The mechanism you need is server push and has a
myriad of solutions (Long polling , Websockets , iframes , Server
Sent Events and more) and is language-agnostic on
the server-side.

You will propably still need JS in the browser though.
Have fun !


ghans