Solving a Rubik's Cube

We bought a Rubik's Cube while away on our summer holiday this year and spent some time playing around with it and then learning to solve it.  We've returned to it over the Christmas break.  The solve we're learning is based on a very detailed video (below) from Wired Magazine.  I'm at the stage where I can remember most of the solve shown in the video but haven't memorised the final few steps involving the algorithms to position the final corner pieces in the top layer.

Since the video is so long and detailed, when you're at the stage of being able to remember most of the solve, you just need a quick memory jogger rather than wading through the video (even though it has some nice chapter markings).  Hence, this post is my quick reference guide for the future.  I'll walk through the whole solve very briefly (use the video for the detail)...

Introduction

Learn the right trigger and left trigger moves (involves holding the cube correctly)

Learn cube notation (rotate the appropriate face clockwise from the point of view of you looking straight onto that face)

• F = Front Face

• B = Back

• L = Left

• R = Right Face

• D = Downward Face

• U = Upward Face

• ‘ = Spin anti clockwise e.g. F’ = Front Face anti clockwise

• 2 Spin twice e.g. F2 = Front Face rotates by 180 degrees (spun twice)

 

Solve the bottom layer

Video Link

1. Make the daisy
1. Position white edge pieces around the yellow centre
2. Make a white cross on the bottom face
1. Line up white edge stickers on the top face with their middle colour on the side face, rotate the twice to move the white sticker from the top face to the bottom face
2. The white face should remain pointing down for the rest of the solve
3. Position the bottom row corners
1. Search for corner pieces in the top layer that have a white piece
1. If found, match the non-white colour of the corner piece in the top layer (ignore the top face) with the coloured center.
2. With the non-white coloured center facing you observe whether the white sticker is on the left or right side of the cube. If left, perform the left trigger; if right, perform the right trigger.
2. If there are no white pieces in the top layer but you have one in the bottom layer. Determine if the white piece in the bottom layer is on the left or right and with the white piece facing you, perform the left or right trigger (depending on whether the white piece is on the left or right side of the cube). The white piece will now be on the top of the cube.
   
3. If there are no white pieces in the top layer but you have one on the top face. Rotate the top face such that the white sticker is not opposite a white sticker on the bottom face i.e. the white sticker on the top face should be opposite a coloured sticker on the bottom face. Then reposition the sticker so it’s in the top layer.
1. Perform the left or right trigger twice in succession if depending on whether the white sticker on the top face is on the left or right side of the cube.  Now refer to 3.1 to place the corner correctly onto the bottom face.

 

Solve the middle layer

Video Link

1. Search the top layer for edge pieces that do not have any yellow stickers (either on the edge face or the top face).  Then once found move that piece to the second layer.
   
1. Rotate the top layer such that the sticker on the edge face is colour matched with its centre sticker.
2. Examine the colour of the sticker on the top face of the edge piece you're moving, it should match the left or right centre stickers.
1. If it matches the left then rotate the top face anti clockwise by 90 degrees (a U' in notation form) then perform a left trigger
2. If it matches the right then rotate the top face clockwise by 90 degrees (a U in notation form) then perform a right trigger
3. You've now displaced one of the white stickers.  It will be in the top row so simply place it back to the bottom face using the same method as when solving the bottom layer.
2. Repeat the above until there are no more non-yellow stickers on the top face.
3. You may occasionally find a situation where there are no edge pieces in the top layer without yellow stickers but the second layer is not complete.  If this happens:
1. Examine the middle layer for the piece that is not right.  With that piece facing you, examine if it's on the left or right of the cube.  Perform either the left or right trigger according to which side its on.
2. Fix the displaced white piece.
3. There will now be an edge piece in the top layer that doesn't have a yellow sticker so continue solving as per the first step of the middle layer.

 

Create a Yellow Cross (top face)

Video Link

Required Algorithm: F U R U' R' F'

1. Repeat these steps depending on the number of yellow edge pieces (on the top face):
   
1. If there are no yellow edge pieces (on the top face), perform the algorithm.
2. If there are two yellow edge pieces in a line, orient the line so it faces up/down, perform the algorithm.
3. If there are two yellow edge pieces next to each other, place them in the 12 and 9 position on the top face, perform the algorithm.

 

Solve the Yellow Face

Video Link

Required Algorithm: R U R' U R U2 R'

1. Look at the top (yellow) face and repeat these steps depending on the number of yellow corner pieces (on the top face):
1. If there are zero or two yellow corner stickers, rotate the top face until there is a yellow sticker in the top right position of the left face, perform the algorithm.
2. If there is one yellow corner sticker, rotate the top face until the corner sticker is in the bottom right position, perform the algorithm.

 

Position the Top Layer Corners

Video Link

 

Required Algorithm: L' U R U' L U R' R U R' U R U2 R'

1. Look at the top corner pieces of the top layer, repeat these steps:
1. If there are no matching corner pieces, perform the algorithm.
2. If one of the faces has matching corner pieces, place that face in the left hand so it's pointing left, perform the algorithm.
2. When all of the corner pieces match, rotate the upper face so the corner pieces on each face match up with their centre colour.

Position the Top Layer Edges

Video Link

Required Algorithm (Clockwise) i: F2 U R' L F2 L' R U F2

 

Required Algorithm (Anticlockwise) ii: F2 U' R' L F2 L' R U' F2

1. If one of the sides is solved, face it away from you then look at the edge pieces on the remaining unsolved 3 sides
1. Swap the edges clockwise, perform algorithm i
2. Swap the edges anticlockwise, perform algorithm ii
2. If none of the sides are solved, perform algorithm ii, reposition the cube to face the solved face away from you and then perform algorithm ii again.
   

IoT Christmas Tree Tech

In my previous post where I was showing off my IoT Christmas Trees, I described the project and what the trees are intended to do.  This post features the inside track information about how I put the project together.  So the first post is supposed to be non-technical if you will and this post details the info more of interest to those interested in the technical make-up of the project.  Since this is effectively a recipe for how to create one of my IoT Christmas Trees, we'll start with the list of things needed.

Ingredients

For the Tree

Bits you need to make one tree:

• Wood
• Paint
  
• Arduino ESP32
• Micro USB Cable
• Veroboard
• LED String
• Buttons
  

Server and Connection Requirements

These are Internet connected of course so needed here are:

• An MQTT Broker
  
• An HTTP Server
• WiFi with Internet Connection
• Another WiFi capable device
  

Other Useful Bits

Probably staple provisions of any maker's tool box:

• Glue Gun
• Soldering Iron and Solder
• Heat Shrink Tubing
• Wire (22AWG Solid Core)

 

Putting it all together

 

The wooden bits

You need enough wood in whatever design you prefer.  I made a point of making each of my trees in a different style.  It caused more work that way of course but there's something nice about each tree being unique.  My designs are all between about 25cm and 40cm tall without much thought put into why.  However, this sort of size seems to work well with the light string I chose.  Given the light string is 5 metres long and I used half a string for each tree I needed to hang 2.5m of string around each tree (containing 25 lights per tree).  Therefore, you need to size the wooden structure appropriately for the length of string or number of lights you intend to hang.

Painting

I decided to use spray paint to try and achieve a really smooth and high quality finish.  I selected Montana paints as they provided all the types of paint I wanted to use (primer, metallic top coat, glitter and varnish).  I went with 4 of their colours, Aztec Gold, Avocado Green, Titanium, Red; and glitter effects in Silver and Dusty Gold.  Everything came from Graff City.

A couple of coats of primer were needed followed by a couple of coats of metallic.  The glitter paint goes on as a varnish layer with particles of coloured glitter in it and they recommend a top coat of varnish is used to seal the glitter coat and prevent and loose glitter falling off.  The result is a really nice layered effect where the fairly reflective metallic coating is set off against a subtle glitter effect and everything is finished off with the sheen of varnish.

Electronics

The main driver of the project, electronically, is an ESP32 board.  The board I chose is a knock off of the Lolin D32 simply because it has everything I needed (including having the pins not soldered) and much cheaper than locally available boards in the UK.  While the board was cheaper, I did discover some of the drawbacks in as much as it doesn't have built-in pull up resistors on its GPIO pins and as such I had a lot more soldering to do to work in a 10kΩ resistor into a little veroboard circuit to wire in the buttons I chose.

The string of LED lights looks very cool with some quite presentable wiring between the lights when compared to an LED strip.  They're completely WS2812/NeoPixel compatible so they're easy to programme and there's some nifty libraries out there already available.  They are, however, fairly hellish to solder since the wires are coated with some very thin plastic insulation which is either difficult to remove or otherwise burn through with your solder.

Finally, the whole thing is powered via Micro USB so I ordered a pile 3m long USB-A to Micro-USB cables so the trees can be sited a reasonable distance from a power socket and I didn't have to worry about batteries or charging although battery powering these units would definitely be possible.

Firmware

The firmware is a fairly standard Arduino implementation for the main loop and using WifiManager to configure the ESP32 WiFi to connect to an SSID.  It wont come as any surprise to find the messaging component I'm using is based on MQTT and so I'm using Nick's pubsubclient library on the client side.

One of the more interesting things I've done with the firmware is to attempt to make it as remotely configurable as possible without the need to rely on over-the-air updates for the firmware.  To this end, I'm using the inih library and the firmware downloads its configuration as an ini formatted file from a remote location that allows me to configure as much as possible, currently: mqtt hostname:port, username, password, SSL settings, publish and subscribe topics, device name; and then configurations for the lights for things like which colours to cycle around, how long the "Merry Christmas" setting is maintained before reverting to the previous setting.  The ini file format also allows an easy "global" configuration to apply across each tree while also allowing a per-tree customisation.  Should the WiFi connection not be available or the configuration file not be available then the tree reverts to a sensible set of defaults.

Once running, WiFi connected, MQTT connected and the configuration has been downloaded and applied there's some basic login there to cycle between the different light configurations when the left button on the tree is pressed.  This is all done locally on each tree.  The right button, when pressed, sends a (configurable) message to the other trees that tells them what to do.  So it would be possible for each tree to have its own specific "Merry Christmas" pattern so you could, for example, work out who had sent you the message by the pattern/colour of the light flashes on the receiving tree.

I have also built in a simple command protocol to further take advantage of the MQTT connectivity.  This allows me to send a "ping" to each tree to see which are currently alive, connected and working properly.  The second command I have is a "reload" command that will cause the tree to download and re-apply the configuration from its remote location, noting of course that the configuration could have changed and so I can cause a tree to remotely update its configuration.  Finally, there is a "reconnect" command that will cause the tree to disconnect and connect to its configured MQTT broker.  This is useful in the rare circumstance where the IP address of the broker may have changed in which case I can update the configuration, have the tree read a new configuration, then have the tree disconnect from the current broker and connect to a new broker.

MQTT Broker

The MQTT broker is provided courtesy of my still relatively new Pi4 home server and the rather excellent Mosquitto MQTT broker.  Since I'm running this all myself and not using a cloud based MQTT service I've screwed it all down as far as I can from a security perspective but there's nothing like running your own services to make you feel vulnerable!

IoT Christmas Trees

My latest maker project has been running for a good chunk of the year and has been a really cool thing to do to keep me occupied during lockdown since I'm not really one to binge watch box sets.  I've been making Internet connected Christmas trees as gifts for close family.  They're designed to be ambient ornamental decorative pieces with a funky twist of interactivity.  The video I produced probably explains them best...

As you can see from the video, each tree is deliberately different.  I thought it would be more interesting to have a completely different wooden design for each.  My dad did the woodwork which saved me quite a lot of time and allowed me to concentrate on writing the software and doing the electronics not to mention building and painting each tree.  There's a good few hours work in each of these things.

Operation of the trees is pretty simple with the most complicated bit, like with most of these things, being the initial set up to get them onto your WiFi network.  For that, and to explain the basics of how they work along with a bit of troubleshooting information, I wrote a little user manual to go with them.  After all, it will be our closest family members that receive one of these and so I can always help out remotely (and potentially fix any issues that arise).  The left button on each tree cycles round a set of pre-defined colour schemes.  However, these can be changed on a per tree basis should someone want a different colour or configuration.  Similarly, the trees can be operated remotely but I've yet to write a decent interface to do so.  The right button on each tree is where the fun is, causing all the other trees to change light pattern for some period of time.  Again, this is all configurable per tree but by default they all cause the same green and red frenzied light pattern which should be very noticeable in the corner of your room should it occur.

Finally, big thanks to James Sutton and his original iotree project was in no small amount an inspiration for my work here.  Although, the implementations are different both physically and in software there's still a huge amount of overlap.  James was also responsible for running an IoT hackathon at work (we're colleagues) introducing a lot of the technology I would need in order to perform this build.  Thanks again, James!

I've also written more details on the technical implementation.  But, I'll sign this post off with a closer look at each tree in pictures...

 

Yet Another New Home Server

This year has seen me doing more in the way of little tech projects at home than I have done for a while, perhaps due to covid lock downs so if that's the case then I'll take this small positive from an otherwise rubbish situation.  Typically for me, these projects have focused around open source projects and some IoT.  More on those in some separate blog posts when I get around to writing them up.  But for now, I wanted to make some notes on my new home server set up.

I've had an array of different low powered home servers of the years that I've previously written about, namely the NSLU2, TinyTuxBox, Joggler and for the past many years a simple ReadyNAS box that I specifically bought for the Intel processor as it made compiling different bits and pieces a whole lot easier back in the day.  However, I have recently relegated the ReadyNAS box from home serving duties, keeping it only for its native NAS services because using it for other things has become increasingly difficult without updating the entire base OS (which is possible by I'm reluctant to do) due to down level software libraries like an ancient version of openssl.

In with the new then and I moved away from Intel architecture as it's now so much easier to compile for Arm chips and went with the, wait for it, drum roll, rather obvious choice of a Raspberry Pi 4.  Specifically, a Pi 4 Model B, 4GB.  I've paired it with the official Pi case power supply, micro HDMI cable and shoved in an A2  SanDisk Extreme 64GB SDXC card.

And so to the notes, my initial target for this new box would be as follows:

• The Lounge self hosted web based IRC interface
  
• A Mosquitto MQTT broker
• Node Red for home automation event processing
• An NGINX reverse proxy
  
• letsencrypt certificates for all of the above
  

The Lounge

IRC might be a bit old hat but tons of open source project still use it for their more synchronous communications.  ZNC is the choice of old for staying connected to your IRC channels.  For those not familiar, it acts as a relay to the IRC servers you want to connect to.  Effectively, it connects as your IRC client to the servers and presents your local IRC client with an endpoint through which you can connect.  This allows you never to miss any messages and see the IRC conversation even when you're not actually online.  Matrix seems to be taking some of the old IRC community's attention with various projects setting up bridges between Matrix and IRC.  However, the relative newcomer project called The Lounge shows just how far web technologies and web sockets have come.  It's a darned site (pun intended) easier to install configure and use than ZNC so I'm a massive convert and big fan of the project.

The project is relatively stable in the master branch and doesn't release particularly often so I've open for the run from source approach to take advantage of all the latest development.  Other than that, I've only made 3 changes to the default configuration prior to starting up my The Lounge server:

1. host: "127.0.0.1"
2. reverseProxy: true
3. theme: "morning"

As you can see, these are all pretty simple and somewhat trivial changes.  The host setting binds the listener to the localhost interface, thus making it suitable for use with a reverse proxy and not exposing the service outside of the Pi 4.  The reverseProxy setting tells the server it's expecting to run behind a reverse proxy (the clue is in the name I guess).  Finally, I've switched to using a dark mode theme rather than the default light mode.  That's it, the remainder of the configuration is all about which IRC servers and channels to connect to along with the usual IRC bits of registering your nick and logging into the nick server.

Mosquitto

This is even simpler to get going than The Lounge due to the fact it's bundled with Raspbian so you can just apt-get install it.  I've created a configuration based on the bundled example config file but changing:

1. pid_file (probably just because I'm old fashioned like that)
2. user (to drop privileges)
3. listener (to specify a port number)
4. certfile and keyfile (for SSL)
5. log_dest (create a specific log file for the broker)
6. clientid_prefixes (a bit of added security to only allow certain client IDs to connect to the broker)
7. allow_anonymous (quite an important one!)
8. password_file (so that connections are authenticated)

Hopefully, that gives me something secure as well as providing me with the broker functionality that I need.

Node Red

Again, simple to install as it's bundled with Raspbian.  It does like to run under the default "pi" user though, which is a bit of a shame security wise.  All I've done to the configuration is ensure it's listening only on the local interface and enable the adminAuth section such that I'm required to enter a user name and password to access the user interface.

NGINX

 

Another simple install due to using the bundled version that comes with Raspbian.  However, this time around there's a lot more configuration to do since I'm using it to front a reverse proxy onto The Lounge and Node Red.  This gives me a few advantages such as being able to restart NGINX in order to load new SSL certificates without interrupting the underlying services i.e. something like IRC can stay connected even though new certs are loaded.  Both The Lounge and Node Red support SSL in their configuration so this also means I only need to configure certificates in one place and have a single route through which I can access all my home services.  The idea and bulk of the configuration for doing this comes directly from one of the guides available for The Lounge.

server {

    # redirect HTTP traffic to HTTPS
    listen 80 default_server;
    listen [::]:80 default_server;
    server_name _;
    return 301 https://$host$request_uri;
}

server {
    # SSL configuration
    #
    listen 443 ssl default_server;
    listen [::]:443 ssl default_server;
    ssl_certificate /path/to/your/server.crt;
    ssl_certificate_key /path/to/your/server.key;

    server_name your.server.name.com;

 

    # Add this if you want to do web serving as well
    root /var/www/html;
    index index.html index.htm; 

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        try_files $uri $uri/ =404;
    }

 

    # Configure reverse proxy for The Lounge
    location ^~ /YOUR_PREFERRED_IRC_URL_GOES_HERE/ {
        proxy_pass http://127.0.0.1:9000/;
        proxy_http_version 1.1;
        proxy_set_header Connection "upgrade";
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_set_header X-Forwarded-Proto $scheme;

        # by default nginx times out connections in one minute
        proxy_read_timeout 1d;
    }

    # Configure reverse proxy for Node Red

    location ^~ /YOUR_PREFERRED_NODERED_URL_GOES_HERE/ {
        proxy_pass http://127.0.0.1:1880/;
        proxy_http_version 1.1;
        proxy_set_header Connection "upgrade";
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_set_header X-Forwarded-Proto $scheme;

        # by default nginx times out connections in one minute
        proxy_read_timeout 1d;
    }
}

 

Let's Encrypt

From Wikipedia: "Let's Encrypt is a non-profit certificate authority run by Internet Security Research Group that provides X.509 certificates for Transport Layer Security encryption at no charge."

The model for using letsencrypt is pretty simple.  They sign your SSL certificates, free of charge, but their signing expires within 90 days.  Hence, they're encouraging a high turnover of certificates by regular renewals.  This means that realistically you need to automate the process of certificate signing.  To do this I'm using the getssl script which makes life extremely easy when coupled with a cron job to kick off the script on a regular basis.  I'm running it every day and the script decides whether to replace my existing certificates.  It all sits there quite nicely running in the background and doesn't get in the way at all, restarting NGINX only when a new certificate is put in place.  Due to the fact that NGINX is decoupled from the services it is proxying the other services aren't interrupted.