Category Archives: Software

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So, building on what I did before with lights and switches as well as the stuff I’ve been hacking together with my Home.API, I thought I’d build something that may actually be of practical use. So, here’s a device that will tell you, before you walk out the door, whether all your doors and windows are shut, and for bonus points, tell you when they were opened and closed.

As you can see from the video, my local Homebase didn’t have all the bits, so you’ll have to use your imagination a little. The “Real” version would use simple magnet + reed switch burglar alarm fittings connected with bell wire to the terminals on your Piface. An indicator panel connected on the PiFace’s output panel should sit somewhere visible by your front door.

The software, again written in python, is very simple. It loops through all 8 input connectors and turns on or off the corresponding light when it reads a switch open and closed, when it detects a change it writes some output to the terminal and writes a message to the system auth log. This last feature is made even more useful if you configure the Raspberry pi to send its logs to a central server, as I have previously written about.

The next obvious thing to do is to interface this system with the Home API, which would be straight forward to implement (and I will implement when I get a moment!)

Here’s the circuit:

Click on the circuit to see a larger image…

securitysystem

…and here’s the code:

Enjoy!

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Stepping up from traffic lights last time, I decided this time to have a crack at making a Pelican crossing.

A Pelican crossing is a pedestrian crossing consisting of two sets of traffic lights, a button, and a signal to indicate that it is safe for pedestrians to cross. The sequence that the lights follow is slightly more complex than before:

  • Initially, the traffic signal lights are green and the pedestrian “red man” is on red.
  • When the button is pressed, the traffic signal lights cycle to red.
  • Once the traffic signals are red, the pedestrian signal is set to green and a buzzer sounds for a period of time.
  • When the buzzer has finished beeping, the traffic signals are set on flashing amber and the pedestrian green signal also flashes.
  • After a little while, the traffic signal is reset to green and the pedestrian signal to red.

The Circuit

The circuit for this is slightly more complex.

The traffic signals are now linked, so each red, amber, and green light can be linked in parallel. We introduce two new lights for the pedestrian signal, together with a buzzer.

experiment 2 - traffic lights crossing

I know there are two red/green men in real life, but this is a slight simplification. Just connect red/green leds in parallel for the second set, as we did for the main linked traffic signals.

The Software

The code is fairly similar to before, we extend the class to control three additional outputs – the red and green man and a buzzer, as well as to listen to a given input button press.

The main loop waits for a button press and when detected it toggles the lights, sounds the buzzer, then toggles the lights back.

Here it is in action…


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Home.API The modern world is full of cool gizmos, but our houses are pretty primitive by comparison.

Still, more and more houses are getting water and electricity smart meters of one sort or another. Various new home automation, like the Belkin Wemo, are hitting the market, and that is not to mention all the home brew efforts that various hackers are putting together themselves.

As you can see from other posts on this blog, I’ve been having a bit of fun playing around my Current Cost smart electricity meter, as well as playing around with the Raspberry Pi and PiFace, which has got me thinking about building a number of appliances around the place to solve a number of real world problems around the house – monitoring and controlling a number of things (I’ll post some more on this later).

So, problem is, all these devices have their own ways of talking to them, reading data and controlling them, and I thought it’d be cool if we had a common and easily extensible API, which you could talk to using standard web technologies. Having such a platform would enable people to start wiring things together in unexpected ways, using a variety of different devices, the more apis get added the more possibilities you have!

Introducing Home.API

Hacked together as an itch-scratching weekend project, Home.API is my first stab at solving the problem. It is a PHP 5.3+ web app that runs on a web server and is designed to be easily extensible through simple plugins and human readable configuration files.

Out of the box it includes a couple of demo plugins, and a simple dashboard, although the real power comes from its extensible JSON API which can be accessed by simple web calls.

Key features

  • Simple plugin format and configuration files.
  • Wire up the API in a branch structure which suits, use each plugin multiple times.
  • Simple but powerful development dashboard.
  • Currently a JSON API, but trivial to extend to other output formats using a powerful template system.

Format of an endpoint definition file

You API is defined using one or more configuration files in the /def directory. The configuration file contains a number of entries, separated by blank lines, each one defines the endpoint, class to use, and any initialisation parameters.

E.g.

/bedroom/light
    class \x10\DimmerLight
    minvalue 0
    maxvalue 50
    deviceIP 192.168.0.45

/hallway/light
    class \x10\DimmerLight
    minvalue 0
    maxvalue 100
    deviceIP 192.168.0.46

Making a call

Making an API call is simply a matter of making a call to a URL http://my.home.api/api/your/endpoint/function.format?param1=xxxx¶m2=yyyy, where function.format is the exposed method of the plugin class, and format is the template to use (e.g. json).

Each of these endpoints can act independently, and in our example you might be able to execute commands like:

http://home.local/api/bedroom/light/currentLevel.json

or

http://home.local/api/bedroom/light/setting.json?level=20

or

http://home.local/api/hallway/light/off.json

Have a play, and let me know what you think!

» Visit the project on Github…