Christmas Lights 2024

It’s become something of a tradition at this point that each year I continue to build upon the interactive Christmas lights which I started in 2020.

Previous iterations:

• 2020
• 2022
• 2023

Now that my kid is walking, the baby bouncer control I added last year is redundant, but is given me the idea of continuing to build upon the lights following his progress stages.
So this year I purchased a Playstation dance mat.

The single board computer that I have been using is pretty much tapped out in terms of resources – trying to add a USB hub in order to connect the controller pulled too much power, so in order to do that would mean having another powered USB socket (currently there are 3, which all powered from a single wall socket, 3 port USB charger)

However the way that I have developed the control software is that it is ultimately a small web server on the local network.

Therefore I can connect the dance mat to a different machine then just have it control the lights over the network. It’s perhaps not the most optimal way of doing things, but is ultimately a temporary installation for a couple of weeks.

To connect the dance mat, I am using a Playstation to USB adapter (it’s a PS2 dance mat).

This shows up under lsusb, and using the details taken from there I can connect it using udev, following the same method that I used in order to connect the treadmill from a different project.

 

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Christmas Lights 2023 - Baby bouncer controlled lights

Back in 2020 I made some Christmas lights that could be controlled via Slack and WhatsApp so that Christmas spirit could cross the void created by Covid-19 and its lockdowns.

In subsequent years I added more features, such as morse code.

So now adding to my over-engineered Christmas lights has become something of its own tradition.

In early December this year, while setting up the decorations and mulling over what new silliness I was going to add to the lights, I was asked to fix my son's baby bouncer/cradle thing.

It's a Fisher Price Kick & Play Calming Vibrations bouncer, which has switches in the foot area which I believe are supposed to trigger lights and sounds.

This particular one was a hand-me-down which had been sat in storage, and the battery terminals are all corroded, making it non-functional.

Fixing it wouldn't really be a big deal, but I remembered that like most newborns, my son loves anything that's bright and shiny and blinky, like Christmas lights.

 

So obviously you can see where this is going...

The arch of the chair detaches, and you can see in one of the mounting points 4 pins.

A quick probe with the multimeter shows that these are two pins for each of the two 'pedal' switches.

To interface this with the existing light setup, I decided to again use the GPIO interface of the PCDuino.

Using the guide from before, I identified the GPIO identifier for two pins that I wanted to use, and enabled them as below. Pin 4 (232) is an input and pin 7 (233) is an output that is set to high simply provide a source, as I wanted to keep the main source pins (3v3 etc) free.

echo 232 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio232/direction
chown -R ant:ant /sys/class/gpio/gpio232
echo 233 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio233/direction
chown -R ant:ant /sys/class/gpio/gpio233/value
echo 1 > /sys/class/gpio/gpio233/value

The two pins were connected with a resistor to create a pull up effect. I had initially tried to have it as a pull down but it seemed to still have a lot of flicker in the output.

I picked the switch with the red foot as this tends to be more how Sam would sit. one side of the switch was connected to ground, and the other to pin 4.

The code

I added a thread to the main application which would read the value of the pin and change the lights accordingly.

Because of the way that /sys/class/gpio/gpio232/value is not actually a real file, it was not possible to hold the file open and continually read the input. Instead I had to create a loop which would constantly open the file and read the value. This does cause some overhead, but isn't too bad because the file is never more than one character long.

I had initially planned that when a change is detected, it would hook into the main code to change the lights, however I found this was causing a lot of deadlock issues. 

Instead, the new thread works very independently - it will pick one of the basic colors at random, and make a simple HTTP request to localhost to invoke the change.

The result

I'm not sure if he's aware of the causation between him moving and the lights changing, but like most babies there's twinkling, blinking and sparkly stuff, he's a fan, so he certainly seems to enjoy it.

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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!