Tag Archives: Node-Red control

Node Red Sunday

Node-RedIt is Sunday, I’ve done my 4,000 steps down to the village for coffee and back and I’m having a play.

I use Node-Red on a Raspberry Pi to control just about everything in two houses – as my confidence in the setup has grown, I’m currently keeping the Pi up 24/7 with no sign of any issues (well, it could ALWAYS be faster). Normally I control the likes of ESP8266 boards with this to do everything from monitoring temperature, pressure and humidity to controlling heating, fans, lights and more.

It occurred to me, as I’ve also had success with my script in getting Node-Red, Sqlite, MQTT and other software running on other SBCs including the really cheap new ones coming out of the woodwork that it would be nice to be able to talk to them with the same software especially those running Armbian as I’ve had a lot of success with that personally.

So I’ve made a start. I thought you might find this preliminary effort interesting.

In my controllers, MQTT is at the heart of everything and facilitates utterly reliable message sending from device to Pi and Pi to device (indeed there is no reason I could not do device to device really). I thought it might be nice to start off with a little bit of code that simulates what the ESP8266s do constantly – turn things on and off.

So typically, given a device called fred, I might turn a relay on or off using MQTT messages:

topic: fred/toesp
payload: {out0:1}

Let me first explain why I do it this way. So MQTT typically works by sending simple messages back and forth – they have a topic (address) and a payload (data).  My devices, for example fred, listen for two topics:

fred/toesp
esp

That way I can send a message to a SPECIFIC device – or to all of them at once (OTA for example)

If the device needs to send messages back they will always be of the form:

fred/fromesp/out0

in this case the payload returned would be the current state of out0.

So that represents the basics. Here I will show how a cheap controller running Node-Red can accept commands – I won’t go into the actual mechanics of turning a light on and off because for example the GPIO commands used in a Raspberry Pi won’t work on a NanoPi NEO – alternative methods are used. I’ll simply cover how to get to that point.

So here is the simplest possible setup on the Pi, to turn a couple of outputs on and off.

MQTT

This is nothing more than 4 INJECT nodes dropped onto a flow along with an MQTT output. Typically the content of one of these nodes might be:

INJECT

Simple enough. When pressed the node outputs a topic of nanopineo2/toesp and a payload of {out0:1}

This would work with one of my ESP8266 units to turn output 0 on. “nanopineo2” is just the name of one of my NEO units running Node-Red.

Here’s what’s at the other end to make this work.

Nanopi Neo

Two MQTT inputs feeding a function. So the function will work if either the generic “toesp” is called or a device-specific version. In that first function I check out the command – really simple – and will be dramatically improved soon.

// An attempt over time to emulate my code in ESP8266 - taking commands from MQTT
// and processing I/O
// for example message {out26:1}

var m=msg.payload;

if ((m.charAt(m.length-1)=="}") && (m.charAt(0)=="{")) // ignore if not in braces
{
    m = m.substring(1, m.length-1);
    var breakup=m.split(":");
    var getname=breakup[0];
    var sendto=breakup[1].split(",")
    
    switch (getname)
    {
    case 'out0' :  msg.topic='out0'; msg.payload=sendto[0]; node.send(msg); break;
    case 'out1' :  msg.topic='out1'; msg.payload=sendto[0]; node.send(msg); break;
    default: break;
    }
}

The output is reduced to the actual command “out0” for example – and a value. So the next item is a switch in this case selecting “out0” or “out1” and ignoring everything else. The outputs from that switch go to functions which simulate actually controlling something – like a LED for example and in my demo the colour of the black dot changes from black to red when you send a command to turn that output on.

if (msg.payload==1)
  { 
      msg.payload="lamp1.val=100"; node.send(msg); 
      node.status({fill:"red",shape:"dot"});      
  }
else
  {
      msg.payload="lamp1.val=0"; node.send(msg); 
      node.status({fill:"black",shape:"dot"});
  }
  

And that is it for now. As you can see, this can RAPIDLY be expanded to cover every port bit available on your micro, it could control PWM etc. The next step will be to take {command:arg1,arg2….arg6} and parse the arguments into an array. That will then allow PWM and other kind of controls. If you really don’t care about pricing you could do the whole lot with a bunch of Raspberry Pis… but with new Orange Pi boards coming out at under a tenner, the options are endless.

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