Slack/Whatsapp controlled colour-changing and morse code Christmas lights

Several years ago I made some Christmas lights that could be controlled via Slack and WhatsApp, and every year since I find that I need to update the interface to these platforms to account for the changes that they make during the year. 

Usability updates

This year whilst I was doing that, I took the opportunity to add a few new features and simplify the interface.

Now it responds to some key words – all, top, bottom, half, alternate, led, and allows the user to specify certain colours by word and all colours by hex code.

Additionally I refined the serial interface to speed things up.

Moving to a single-board computer

 
For my home implementation of this, previously I would just run a USB extension lead from my desktop. 

I have now migrated the code to a PCDuino2 single board computer. This is a 1Ghz Allwinner A10 chip SBC, which also contains Arduino pin headers.

The board is discontinued (I bought this one from Maplin years ago during their closing down sale), and as a result there is little in the way of official repositories or archives for the Ubuntu variant distribution that it runs. Plus it looks like there’s some sketchiness around the official firmwares around the allwinner chip that powers it.

I found a version of Armbian linux for this platform and burnt it to a micro SD card.
This allowed me to get the PCDuino to boot to Armbian.

Unfortunately it looks like there is no real support for installing Armbian to the NAND storage which is on the PCDuino. However, leaving it on the micro SD has some advantages such as easily being able to image and back up the install.

Then it was simply a case of connecting it to the network and updating it, enabling SSHD for ease of maintenance going forward, and installing required tools for the Christmas lights server (JDK and Arduino).

As the PCDuino is not a typical Arduino development board it needs its own board definition to be used with the Arduino IDE, so for now I decided to continue using an externally connected Arduino.

 

Implementing morse code

 
One of the downsides to the set up the I currently have is that the serial data transmission can be disrupted by the update process transferring data from the Arduino to the lights.

The changes I have made reduce the amount of data that is transmitted via serial and so minimize the problem.

However there is additional functionality that I wish to add that will require further data to be transmitted – that is to have a set of lights which flash similarly to regular Christmas lights, but instead of a standard or random pattern, they blink out morse code, based on a message input from the control application.

Rather than cram more functionality into the WS2812 lights that I am currently using, I plan to leave them be and use a regular set of plain white fairy lights for this. Typically I have always decorated our Christmas trees with a multi colours set and a plain white set, so this fits with what I would typically do anyway.

The lights I used are powered from 3xAA batteries (4.5v), which can easily be substituted for USB and powered from a USB hub. To toggle their on and off state, I have used an optocoupler which will be toggled from the PCDuinos GPIO pins.

The ‘arduino-style’ pins of the PCDuino board can be reached in be linux file system via GPIO – similar to the way I toggled an output pin on the frequency switch project.

Seeing is this makes it quite easy to simply toggle a pin on and off, I should be able to use this for the morse code without having to depend on the rather outdated and no longer supported PCDuino board definitions.

Finding the pin reference

 
A ‘gotcha’ about using the sysfs GPIO interface is that the pin numbers as they may have silk screened on the board do not necessarily correlate to the pin numbers in the file system.

The first thing to do is figure out what the pin identifier would be. In this instance, I found some config files for the PCDuino on GitHub.

There lists the PCDuinos GPIO pins and there corresponding identifier, summarised below.

GPIO Pin	Pin ID
0	PI19
1	PI18
2	PH07
3	PH06
4	PH08
5	PB02
6	PI03
7	PH09
8	PH10
9	PH05
10	PI10
11	PI12
12	PI13
13	PI11
14	PH11
15	PH12
16	PH13
17	PH14
18	PH15
19	PH16

I’d decided to use GPIO 8, so the relevant ID is H10

The Sunxi wiki demonstrates how to calculate the relevant GPIO number from that ID

(position of letter in alphabet - 1) * 32 + pin number

so with H10, H is the 8^th letter so

(8-1)*32 + 10 = 234

So with that number calculated, we can export the pin with

echo 234 > /sys/class/gpio/export

which will make ‘gpio234’ available under /sys/class/gpio.

From there we can make it an output, and change the ownership so of it’s value file so that a regular user can write to it.

echo out > /sys/class/gpio/gpio234/direction

chown -R ant:ant /sys/class/gpio/gpio234/value

Then to switch the lights on,

echo 1 > /sys/class/gpio/gpio234/value

and

echo 0 > /sys/class/gpio/gpio234/value

to turn them off

A demo video is below, and as usual the source is available on GitHub.

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Merry Christmas!

 

 

Slack & WhatsApp controlled Christmas Tree Lights

December 2022 update: I've developed this idea further, giving the project more features, including the ability to blink lights in morse code. The original post remains below.

With the Covid-19 pandemic still dragging on, it looks like things won't be back to normal in time for Christmas.

At work there was discussion about Christmas parties, team building exercises, and other such things to try to boost morale.

I'm currently working on a project that uses WS2812 RGB LEDs (which'll no doubt wind up published here eventually), and on a whim, wondered if there existed fairy lights that use the same chip.

Turns out, there are. So obviously I had to buy some.

My Christmas tree is positioned so that is can be seen in the background when I'm on Zoom calls with work, so I thought it'd be fun if I could setup some system that would let my colleagues interact with the lights.

Once the lights arrived and I'd tested them, I got to tearing them down.

Wiring

The power supply/controller is a USB unit. I was powering it from a phone charger adapter. That also contained an infra-red receiver for the included remote. I thought about potentially working that angle, but the remote had limited options, and I wanted to offer more granular control.

From the controller to the lights was just 3 leads, which I rationalised must be +5V, Ground, and Data.

I cut the wire, figured out which was which, and connected in an Arduino. It wasn't able to provide enough current to drive the LEDs itself, to I made use of the existing charger - the charger continued to be connected to +5V and Ground, sharing the ground with the arduino's ground, and then the data line connected to the arduino.

The circuit. It works fine like this for short periods, although I later found adding a 470 Ohm resistor between arduino D12 and the first LED increased reliability over time.

 

Arduino code

I ended up using the PololuLedStrip library, and modifying the existing code for that.

Initially I'd hoped to be able to provide full RGB control, but it just seemed that the sheer amount of data being sent meant bytes were being lost, or I had to slow the data rate down to unusually slow.

Eventually I settled on using 10 preset colours, defined with numbers 0-9, being sent as a 100-character serial string - 1 character (colour) per LED. This seemed to be the best trade off of functionality and reliability.

The code can be found here.

 

The 'server'

This is a simple web server that accepts GET requests for one endpoint, and is simply there to provide a go-between for the messaging apps and the serial port.

As each LED is individually addressable, I wanted to create a format that would give users control at that level. I settled on messages with the following JSON structure

[1,"colour"]

or

[[1,2,3], "colour"]

where the numbers are the IDs of the LEDs, and the string is one of the available colours.

This would let them control either an individual LED or a series of them in an individual command.

Hooking into Slack and WhatsApp

As at work we use Slack, and we have some previous integration with it, it seemed like the obvious choice.

However, their API functionality is heavily focused on HTTP endpoints, and requires a server to interface with it. That's fine for 'proper' development, but when I'm just messing around at home, I don't really want to be dealing with opening up my home network and all that entails.

Really what I wanted was some client-side plugin functionality. There isn't an official API or interface for one, so I had to improvise.

Using the web-browser interface, and making use of Firefox's Javascript console, I added a MutationObserver to the page, and made use of the DOM to narrow in on the message elements, and get the contents of the latest message in whatever chat/channel the user was in.

The javascript for Slack can be found here.

Once retrieved, some basic checks are done to make sure that the message is in a usable format and hasn't been acted upon already, it's then passed to a local server via HTTP, where it's processed, converted to the serial format used by the arduino, and sent onward to it.

After realising how useful MutationObserver is for things like this, it was quite trivial to do the same for WhatsApp.

The finished product

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