Node-RED at Zurich developerWorks days 2013

Node-RED icon
This year I was lucky enough to be asked back to speak at developerWorks days 2013 in Zurich after giving 2 presentations last year.

This year I was presenting on a great piece of work done by Nick O’Leary and Dave Conway-Jones called Node-RED.

Node-RED is a light weight, edge of the network event processing engine. The main aim is to make it easy to bridge a wide variety of input and output sources and to allow logic to be applied to the events/messages that flow between them.

For my presentation I wanted to try and use Node-RED as much as possible so I set about seeing if I could use it to host and control my slide deck. I started out with a impress.js presentation the Nick had written. Impress is a Javascript framework to build HTML5 presentation similar to prezi, but it also exposes an API to drive the slide transitions from and external source. Combining this feature with the MQTT over WebSockets will allow me to drive things remotely.

I added the following bit of code to the end of the presentation.html

<script type="text/javascript" src="js/mqttws31.js"></script>
<script src="js/impress.js"></script>
<script src="js/impressConsole.js"></script>
<script>
    var imp = impress();
    imp.init();

    var client;
    var slide;

    function setupMQTT() {
    	client = new Messaging.Client(document.location.hostname,8181,"presentation");
		client.onConnectionLost = onConnectionLost;
		client.onMessageArrived = onMessageArrived;
		client.connect({onSuccess:onConnect});
    }

   function onConnectionLost(response) {
	setTimeout(setupMQTT, 500);
	document.removeEventListener('impress:stepenter', sendStepEnter);
   }

   function onMessageArrived(message) {
	if (message.payloadString === "next") {
		imp.next();
	} else if (message.payloadString === "prev") {
		imp.prev();
	} else {
		console.log(slide);
		if (slide === "demotimeagain") {
			//update with twitter details
			console.log(message.payloadString)
			obb = JSON.parse(message.payloadString);
			console.log(obb);
			document.getElementById('injected-twitter-screen').innerHTML = obb.sender.screen_name;
			document.getElementById('injected-twitter-id').innerHTML = obb.sender.name;
			document.getElementById('injected-twitter-tweet').innerHTML = obb.body;
		} else {
			imp.goto(message.payloadString);
		}
	}
   }

   function onConnect() {
	client.subscribe("pres");
	document.addEventListener('impress:stepenter', sendStepEnter);
   }

   function sendStepEnter(step) {
	console.log(step.target.id);
	slide = step.target.id;
	message = new Messaging.Message(step.target.id);
	message.destinationName = "slide";
	client.send(message);
    }

    setupMQTT();

</script>

This first sets up impress.js then starts to set up some basic boiler plate to create a MQTT client connection over Web Sockets. The onConnect function subscribes this clients to the ‘pres’ topic that will be used to receive ‘next’ & ‘prev’ messages to advance the slides. It also adds a event listener that receives events from impress.js each time a new slide is displayed.

The onMessage function handles the ‘next’& ‘prev’ and also a couple of special case to populate some data into a slide following a demonstration.

This a basic Node-RED flow to make this all work can be found here

In order to get Node-RED to serve the presentation html and required javascript libraries used to require embedding Node-RED into a custom application, but this requirement was removed with a new feature in Node-RED 0.4.0. 0.4.0 include a new configuration setting called httpStatic which allows you to specify a directory holding a collection of static content, when you use this setting you also need to specify httpRoot to move the Node-RED gui to a different root directory.

The basic version of the presentation is embedded here:

If you click on the slide you can then navigate back and forth using the arrow keys.

You can access it full screen here

Emergency FTTC Router

On Monday I moved to a new broadband provider (A&A). The BT Openreach guy turned up and swapped over the face plate on my master socket, dropped off the FTTC modem, then went and down to the green box in the street and flipped my connection over. It all would have been very uneventful except for the small problem that the new router I needed to link my kit up to FTTC modem had not arrived.

This is because BT messed up the address for where they think my line is installed a few of years ago and I’ve not been able to get them to fix it. A&A quickly sent me out a replacement router with next day delivery but it would mean a effectively 2 days without any access at home.

The routers talks to the FTTC modem using a protocol called PPPoE over normal ethernet. There is a Linux package called rp-pppoe which provides the required support. So to quickly test that the install was working properly I installed this on to my laptop and plugged it directly into FFTC modem. Things looked really good but did mean I was only able to get one device online and I was tied to one end of the sofa by the ethernet cable.

PPPoE is configured the same way PPP used to be used with dial up modems, you just need to create /etc/ppp/pppoe.conf file that looks a bit like this:

ETH=eth0
USER=xxxxxxx
DEMAND=no
DNSTYPE=SERVER
PEERDNS=yes
DEFAULTROUTE=yes
PING="."
CONNECT_POLL=2
CF_BASE=`basename $CONFIG`
PIDFILE="/var/run/$CF_BASE-adsl.pid"
LCP_INTERVAL=20
LCP_FAILURE=3
FIREWALL=NONE
CLAMPMSS=1412
SYNCHRONOUS=no
ACNAME=
SERVICENAME=
CONNECT_TIMEOUT=30
PPPOE_TIMEOUT=80

And include you username and password in the /etc/ppp/chap-secrets. Once set up you just need to run pppoe-start as root

In order to get back to something like normal I needed something else. I had a Raspberry Pi in my bag along with a USB Ethernet adapter which looked like it should fit the bill.

I installed rp-pppoe and the dhcp server then plugged one ethernet adapter into the FTTC modem and the other into a ethernet hub. Into the hub I had a old WiFi access point and the rest of my usual machines. After configuring the Pi to masquerade IP traffic from the hub I had everything back up and running. The only downside is that speeds are limited to 10mbps as that is as quick as the built in ethernet adapter on Pi will do.

Node-Red – Ti SensorTag Node

Last weekend I spent some time working on yet another Node-Red node. This one is an input node that reads the data published by a small sensor platorm from Ti.

The Ti SensorTag is a Bluetooth 4.0 LE platform designed to be a test source for building new BLE and is very accessible at only $25 dollars especially with the following list of sensors on board:

  • Ambient Temperature
  • IR remote Temperature
  • Air Pressure
  • Humidity
  • Accelerometer
  • Magnetometer
  • Gyroscope
  • 2 Push Buttons

Ti have also set up a open wiki to allow people to document they experiments with the device.

You can find the node in the new node-red-nodes repo on github here it relies on a slightly updated version of Sandeep Mistry‘s node-sensortag, the read me explains how to install my update (until I get round to submitting the pull request) but here is the command to run in the root of your Node-Red directory:

npm install sensortag@https://api.github.com/repos/hardillb/node-sensortag/tarball

(you may need to install the libbluetooth-dev package for Debian/Ubuntu based distros and bluez-libs-devel on Redhat/Fedora first)

UPDATE:
Sandeep has now merged my changes so the sensortag node can now be installed normally with npm with:

npm install sensortag

Once installed you need to run Node-RED as root as this is the only way to get access to the BLE functions, then you can add the node to the canvas and configure which sensors are pushed as events

Please feel free to have a play and let me know what you think