17 Aug 2017
Last month, I attended KDE’s annual conference, Akademy. This year, it was held in Almeria, a small Andalusian city on the south-east coast of Spain.
The name of the conference is no misspelling, it’s part of KDE’s age old tradition of naming everything to do with KDE with a ‘k’.
Akademy was a collection of amazing, life-changing experiences. It was my first solo trip abroad and it taught me so much about travel, KDE, and getting around a city half-way accross the world from home.
Travel
My trip began from the recently renamed Kempegowda International Airport, Bangalore. Though the airport is small for an international airport, the small size of the airport works to its advantage as it is very easy to get around. Check-in and immigration was a breeze and I had a couple of hours to check out the loyalty card lounge, where I sipped soda water thinking about what the next seven days had in store.
The first leg of my trip was on a Etihad A320 to Abu Dhabi, a four hour flight departing at 2210 on 20 July. The A320 isn’t particularly unique equipment, but then again, it was a rather short leg. The crew onboard that flight seemed to be a mix of Asian and European staff.
Economy class in Etihad was much better than any other Economy class product I’d seen before. Ample legroom, very clean and comfortable seats, and an excellent IFE system. I was content looking at the HUD-style map visualisation which showed the AoA, vertical speed, and airspeed of the airplane.
On the way, I scribbled a quick diary entry and started reading Part 1 of Sanderson’s Stormlight Archive - ‘The Way of Kings’.
Descent to Abu Dhabi airport started about 3:30 into the flight. Amber city lights illuminated the desert night sky. Even though it was past midnight, the plane’s IFE reported an outside temperature of 35C. Disembarking from the plane, the muggy atmosphere hit me after spending four hours in the plane’s air-conditioned cabin.
The airport was dominated by Etihad aircraft - mainly Airbus A330s, Boeing 787-8s, and Boeing 777-300ERs. There were also a number of other airlines part of the Etihad Airways Partners Alliance such as Alitalia, Jet Airways, and some Air Berlin equipment. As it was a relatively tight connection, I didn’t stop to admire the birds for too long. I traversed a long terminal to reach the boarding gate for the connecting flight to Madrid.
The flight to Madrid was another Etihad operated flight, only this time on the A320’s larger brethren - the A330-200. This plane was markedly older than the A320 I had been on the first leg of the trip. Fortunately, I got the port side window seat in a 2-5-2 configuration. The plane had a long take-off roll and took off a few minutes after 2am. Once we reached cruising altitude, I opened the window shade. The clear night sky was full of stars and I must have spent at least five minutes with my face glued to the window.
I tried to sleep, preparing myself for the long day ahead. Soon after waking up, the plane landed at Madrid Barajas Airport and taxied for nearly half-an-hour to reach the terminal. After clearing immigration, I picked up my suitcase and waited for a bus which would take me to my next stop - the Madrid Atocha Railway Station. Located in the heart of city, the Atocha station is one of Madrid’s largest train stations and connects it to the rest of Spain. My train to Almeria was later that day - at 3:15 in the afternoon.
On reaching Atocha, I got my first good look at Madrid.
My facial expression was quite similar
I was struck by how orderly everything was, starting with the traffic. Cars gave the right of way to pedestrians. People walked on zebra crossings and cyclists stuck to the defined cycling lanes. Things taken for granted in developed countries looked like a world apart from Bangalore. Shining examples of Baroque and Gothic architecture were scattered among newer establishments.
Having a few hours to kill before I had to catch my train, I roamed around Buen Retiro Park, one of Spain’s largest public parks. It was a beautiful day, bright and sunny with the warmth balanced out by a light breeze.
My heavy suitcase compelled me to walk slowly which made me take in as much as I could. Retiro Park is a popular stomping ground for joggers, skaters, and cyclists alike. Despite it being 11am on a weekday, I saw plenty of people jogging though the Park. After this, I trudged through some quaint neighbourhoods with cobbled roads and old apartment buildings dotted with small shops on the ground floor.
Maybe it was the sleep-deprivation or dehydration after a long flight, but everything felt so surreal! I had to pinch myself a few times - to believe that I had come thousands of miles from home and was actually travelling on my own in a foreign land.
I returned to Atocha and waited for my train. By this time, I came to realise that language was going to be a problem for this trip as very few people spoke English and my Spanish was limited to a few basic phrases - notably ‘No hables Espanol’ and ‘Buenos Dias’ :P Nevertheless, the kind folks at the station helped me find the train platform.
Trains in Spain are operated by state-owned train companies. In my case, I would be travelling on a Renfe train going till Almeria. The coaches are arranged in a 2-2 seating configuration, quite similar to those in airplanes, albeit with more legroom and charging ports. The speed of these trains is comparable to fast trains in India, with a top speed of about 160km/hr. The 700km journey was scheduled to take about 7 hours. There was plenty of scenery on the way with sloping mountain ranges and deserted valleys.
Big windows encouraged sightseeing
After seven hours, I reached the Almeria railway station at 10pm. According to Google Maps, Residencia Civitas, the hostel which KDE had booked for all the attendees was only 800m away - well within walking distance. However, unbeknownst to me, I started walking in the opposite direction (my phone doesn’t have a compass!). This kept increasing the Google Maps ETA and only when I was 2km off track I realised something was very wrong. Fortunately, I managed to get a taxi to take me to Residencia Civitas - a university hostel where all the Akademy attendees would be staying for the week.
After checking in to Civitas, I made my way to the double room. Judging from the baggage and the shoes in the corner, someone had moved in here before I did. About half an hour later, I found out who - Rahul Yadav, a fourth year student at DTU, Delhi. Exhausted after an eventful day of travel, I switched off the lights and went to sleep.
The Conference
The next day, I got to see other the Akademy attendees over breakfast at Civitas. In all, there were about 60-70 attendees, which I was told was slightly smaller than previous years.
The conference was held at University of Almería, located a few kilometres from the hostel. KDE had hired a public bus for transport to and from the hostel for all the days of the conference. The University was a stone’s throw from the Andalusian coastline. After being seated in one of the larger lecture halls, Akademy 2017 was underway.
Konqi! And KDE Neon!
The keynote talk was by Robert Kayne of Metabrainz, about the story of how MusicBrainz was formed out of the ashes of CDDB. The talk set the tone for the first day of Akademy.
The coffee break after the first two talks was much needed. I was grappling with sleep deprivation and jet lag from the last two days and needed all the caffeine and sugar I could get to keep myself going for the rest of the day. Over coffee, I caught up with some KDE developers I met at QtCon.
Throughout the day, there were a lot of good talks, notably ‘A bit on functional programming’, and five quick lightning talks on a variety of topics. Soon after this, it was time for my very own talk - ‘An Introduction to the KIO Library’.
The audience for my talk consisted of developers with several times my experience. Much to my delight, the maintainer of the KIO Library, David Faure was in the audience as well!
Here’s where I learned another thing about giving presentations - they never quite go as well as it seems to go when rehearsed alone. I ended up speaking faster than I planned to, leaving more than enough time for a QA round. Just as I was wary about, I was asked some questions about the low-level implementation of KIO which thankfully David fielded for me. I was perspiring after the presentation, and it wasn’t the temperature which was the problem 😅 A thumbs up from David afterwards gave me some confidence that I had done alright.
Following this, I enjoyed David Edmundson’s talk about Binding properties in QML. The next presentation I attended after this is where things ended up getting heated. Paul Brown went into detail about everything wrong with Kirigami’s TechBase page. This drew some, for lack of a better word, passionate people to retaliate. Though it was it was only supposed to be a 10 minute lightning talk, the debate raged on for half-an-hour among the two schools of thought of how TechBase documentation should be written. The only thing which brought the discussion to an end was the bus for returning to Civitas leaving sharp at 8pm.
Still having a bit of energy left after the conference, I was ready to explore this Andalusian city. One thing which worked out nicely on this trip is the late sunset in Spain around this time of the year. It is as bright as day even at around 9pm and the light only starts waning at around 930pm. This gave Rahul and me plenty of time to head to the beach, which was about a 20 minute walk from the hostel.
Here, it struck me how much I loved the way of life here.
Unlike Madrid, Almeria is not a known as a tourist destination so most of the people living there were locals. In a span of about half an hour I watched how an evening unfolds in this city. As the sun started dipping below the horizon, families with kids, college couples, and high-school friends trickled from the beach to the boardwalk for dinner. A typical evening looked delightfully simple and laid-back in this peaceful city.
The boardwalk had plenty of variety on offer - from seafood to Italian cuisine. One place caught my eye, a small cafe with Doner Kebab called ‘Taj Mahal’. After a couple of days of eating nothing but bland sandwiches, Rahul and I were game for anything with a hint of spice of it. As I had done in Madrid, I tried ordering Doner Kebab using a mixture of broken Spanish and improvised sign language, only to receive a reply from the owner in Hindi! It turned out that the owner of the restaurant was Pakistani and had migrated to Spain seven years ago. Rahul made a point to ask for more chilli - and the Doner kebabs we got were not lacking in spice. I had more chilli in that one kebab than I normally would have had in a week. At least it was a change from Spanish food, which I wasn’t all that fond of.
View from the boardwalk
The next day was similar to the first, only a lot more fun. I spent a lot amount of time interacting with the people from KDE India. I also got to know my GSoC mentor, Boudhayan Gupta (@BaloneyGeek). The talks for this day were as good as the ones yesterday and I got to learn about Neon Docker images, the story behind KDE’s Slimbook laptop, and things to look forward to in C++17/20.
The talks were wrapped up with the Akademy Awards 2017.
David Faure and Kevin Ottens
There were still 3 hours of sunlight left after the conference and not being ones to waste it, we headed straight for the beach. Boudhayan and I made a treacherous excursion out to a rocky pier covered with moss and glistening with seawater. My well-worn sandels were the only thing keeping me from slipping onto a bunch of sharply angled stones jutting out from the waves. Against my better judgement, I managed to reach the end of the pier only to see a couple of crabs take interest in us. With the tide rising and the sun falling, we couldn’t afford to stay much longer so we headed back to the beach just as we came. Not long after, I couldn’t help myself and I headed into the water with enthusiasm I had only knew as a child. Probably more so for BaloneyGeek though, who headed in headfirst with his three-week-old Moto G5+ in his pocket (Spoiler: the phone was irrevocably damaged from half a minute of being immersed in saltwater). In the midst of this, we found a bunch of KDE folks hanging out on the beach with several boxes of pizza and bottles of beer. Free food!
Exhausted but exhilarated, we headed back to Civitas to end another very memorable day in Almeria.
Estacion Intermodal, a hub for public transport in Almeria
With the talks completed, Akademy 2017 moved on to its second leg, which consisted more of BoFs (Birds of a Feather) and workshops.
The QML workshop organised by Anu was timely as my relationship with QML has been hot and cold. I would always go in circles with the QML Getting Started tutorials as there aren’t as many examples of how to use QtQuick 2.x as there are with say, Qt Widgets. I understood how to integrate JavaScript with the QML GUI and I will probably get around to making a project with the toolkit when I get the time. Paul Brown held a BoF about writing good user documentation and deconstructed some more pretentious descriptions of software with suggestions on how to avoid falling into the same pitfalls. I sat on a few more BoFs after this, but most of the things went over my head as I wasn’t contributing to the projects discussed there.
Feeling a bit weary of the beach, Rahul and I decided to explore the inner parts of the city instead. We planned to go to the Alcazaba of Almeria, a thousand-year-old fortress in the city. On the way, we found a small froyo shop and ordered a scoop with chocolate sauce and lemon sauce. Best couple of euros spent ever! I loved the tart flavour of the froyo and how it complemented the toppings with its texture.
This gastronomic digression aside, we scaled a part of the fort only to find it locked off with a massive iron door. I got the impression that the fort was rarely ever open to begin with. With darkness fast approaching, we found ourselves in a dodgy neighbourhood and we tried to get out as fast as we could without drawing too much attention to ourselves. This brought an end to my fourth night in Almeria.
View from Alcazaba
The BoFs continued throughout the 25th, the last full day of Akademy 2017. I participated in the GSoC BoF where KDE’s plans for future GSoCs, SoKs, and GCIs were discussed (isn’t that a lot of acronyms!). Finally, this was one topic where I could contribute to the discussion. If there was any takeaway from the discussion for GSoC aspirants, it is to start as early as you can!
I sat on some other BoFs as well, but most of the discussed topics were out of my scope. The Mycroft and VDG BoF did have some interesting exchange of ideas for future projects that I might consider working on if I get free time in the future.
Rahul was out in the city that day, so I had the evening to explore Almeria all by myself.
I fired up Google Maps to see anything of interest nearby. To the west of the hostel was a canal I hadn’t seen previously so I thought it would be worth a trip. Unfortunately, because of my poor navigation skills and phone’s lack of compass, I ended up circling a flyover for a while before ditching the plan. I decided to go to the beach as a reference point and explore from there.
What was supposed to be a reference point ended up becoming the destination. There was still plenty of sunlight and the water wasn’t too cold. I put one toe in the water, and then a foot.
And then, I ran.
Running barefoot alone the coastline was one of the best memories I have of the trip. For once, I didn’t think twice about what I was doing. It was pure liberation. I didn’t feel the exertion or the pebbles pounding my feet.
Almeria’s Beaches
The end of the coastline had a small fort and a dirt trail which I would’ve very much wanted to cycle on. After watching the sun sink into the sea, I ran till the other end of the boardwalk to find an Italian restaurant with vegetarian spinach spaghetti. Served with a piece of freshly baked bread, dinner was delicious and capped off yet another amazing day in Almeria.
Dinner time!
Day Trip
The 26th was the final day of the conference. Unlike the other days, the conference was only for half a day with the rest of the day kept aside for a day trip. I cannot comment on how the conference went on this day as I had to rush back to the hostel to retrieve my passport, which was necessary to attend the day trip.
Right around 2 in the afternoon we boarded the bus for the day trip. Our first stop was the Plataforma Solar de Almería, a solar energy research plant in Almeria. It houses some large heliostats for focussing sunlight at a point on a tower. This can be used for heating water and producing electricity.
There was another facility used for testing the tolerance of spacecraft heat shields by subjecting them to temperatures in excess of 2000C by focussing sunlight.
Heliostats focus at the top of the tower
The next stop was at the San José village. Though not too far from Almeria, the village is frequented by tourists much more than Almeria is and has a very different vibe. The village is known for its beaches, pristine clear waters, and white buildings. I was told that the village was used in the shooting of some films such as The Good, The Bad, and The Ugly.
Our final stop for the day was at the Rodalquilar Gold Mine. Lost to time, the mine had been shut down in 1966 due to the environmental hazards of using cyanide in the process to sediment gold. The mine wouldn’t have looked out of place in a video-game or an action movie, and indeed, it was used in the filming of Indiana Jones and the Last Crusade. There was a short trek from the base of the mine to a trail which wrapped around a hill. After descending from the top we headed back to the hostel.
This concluded my stay in Almeria.
Madrid
After checking out of the hostel early the next morning, I caught a train to Madrid. I had a day in the city before my flight to Bangalore the next day.
I reached Atocha at about 2 in the afternoon and checked in to a hotel. I spent the entire evening exploring Madrid on foot and an electric bicycle through the BiciMAD rental service.
Photo Dump
The Return
My flight back home was on the following morning, on the 28 July. The first leg of the return was yet again, on an Etihad aircraft bound for Abu Dhabi. This time it was an A330-300. It was an emotional 8 hour long flight - with the memories of Akademy still fresh in my mind. To top it off, I finished EarthBound (excellent game!) during the flight.
Descent into Abu Dhabi started about half an hour before landing. This time though, I got to see the bizarre Terminal 1 dome of the Abu Dhabi airport. The Middle East has always been a mystical place for me. The prices of food and drink in the terminal were hard to stomach - 500mL of water was an outrageous 8 UAE Dirhams (₹140)! Thankfully it wasn’t a very long layover, so I didn’t have to spend too much.
Note to self: may cause tripping if stared at for too long
The next leg was a direct flight to Bangalore, on another Etihad A330. Compared to all the travel I had done in the last two days, the four hour flight almost felt too short. I managed to finish ‘Your Lie in April’ on this leg.
I had mixed emotions on landing in Bangalore - I was glad to have reached home, but a bit sad that I had to return to college in only two days.
Akademy 2017 was an amazing trip and I am very grateful to KDE for letting me present at Akademy and for giving me the means of reaching there. I hope I can make more trips like these in the future!
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20 Jul 2017
As a school kid, I was always fascinated by meeting college students from top tier colleges.
There was something surreal in the way they talked and they confidently stood with T-shirts proudly proclaiming the name of their alma mater. I used to have the impression that no matter what came in the future, there was a certain justification of their abilities and intelligence. Perhaps society had conditioned me to think as such. Maybe their apparent confidence was a just a projection of how I thought it would feel to be in a top tier college.
It struck me just recently that everyone in my college is of the same surreal breed I used to look upto. But now, the magic is lost on me. It’s no longer the case that simply being admitted to a Tier-1 college would give one opportunities otherwise impossible. At the same time, the name of the college on your degree matters little if you haven’t done enough legwork in college to justify being called an “Engineer”.
04 Jul 2017
It’s been almost a year since I finished my GSoC project for implementing discontinuous file selections as a KIOSlave.
The ioslave is now officially shipped in the KDE ExtraGear Utils software package and it can be downloaded from here: https://download.kde.org/stable/kio-stash/kio-stash-1.0.tar.xz.mirrorlist
Introduction
Selecting multiple files in any file manager for copying and pasting has never been a pleasant experience, especially if the files are in a non-continuous order. Often, when selecting files using Ctrl+A or the selection tool, we find that we need to select only a subset of the required files we have selected. This leads to the unwieldy operation of removing files from our selection. Of course, the common workaround is to create a new folder and to put all the items in this folder prior to copying, but this is a very inefficient and very slow process if large files need to be copied. Moreover Ctrl+Click requires fine motor skills to not lose the entire selection of files.
This is an original project with a novel solution to this problem. My solution is to add a virtual folder in all KIO applications, where the links to files and folders can be temporarily saved for a session. The files and folders are “staged” on this virtual folder. Files can be added to this by using all the regular file management operations such as Move, Copy and Paste, or by drag and drop. Hence, complex file operations such as moving files across many devices can be made easy by staging the operation before performing it.
Project Overview
This project consists of the following modules. As there is no existing implementation in KIO for managing virtual directories, all the following modules were written completely from scratch.
KIO Slave
The KIO slave is the backbone of the project. This KIO slave is responsible for interfacing with the GUI of a KDE application and provides the methods for various operations such as copying, deleting, and renaming files. All operations on the KIO slave are applied on a virtual stash filesystem (explained below). These operations are applied through inter process communication using the Qt’s D-Bus API.
The advantage of the KIO slave is that it provides a consistent experience throughout the entire KDE suite of applications. Hence, this feature would work with all KIO compatible applications.
Stash File System
The Stash File System (SFS) is used for virtually staging all the files and directories added to the ioslave. When a file is copied to the SFS, a new File Node is created to it under the folder to which it is copied. On copying a folder, a new Directory Node is created on the SFS with all the files and directories under it copied recursively as dictated by KIO. The SFS is a very important feature of the project as it allows the user to create folders and move items on the stash ioslave without touching the physical file system at all. Once a selection is curated on the ioslave, it can be seamlessly copied to the physical filesystem.
The SFS is implemented using a QHash pair of the URL as a key, containing the location of the file on the SFS and the value containing a StashNodeData object which contains all the properties (such as file name, source, children files for directories) of a given node in SFS.
Memory use of the SFS is nominal on a per file basis - each file staged on the SFS requires roughly 300 bytes of memory.
Stash Daemon
The Stash File System runs in the KDE Daemon (kded5) container process. An object of the SFS is created on startup when the daemon is initialized. The daemon responds to calls from the ioslave communicated over the session bus and creates and removes nodes in the SFS.
Installation
Make sure you have KF5 backports with all the KDE dependency libraries installed before you build!
Download the tarball to your favorite folder, extract, and run:
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr -DKDE_INSTALL_USE_QT_SYS_PATHS=TRUE ..
make
sudo make install
kdeinit5
Result
Open Dolphin and set the path as stash:/. This directory is completely ‘virtual’ and anything added to it will not consume any extra disk space. All basic file operations such as copy, paste, and move should work.
Folders can be created, curated, and renamed on this virtual folder itself. However, as this is a virtual directory, files cannot be created on it.
Copying from remote locations such as mtp:/ may not work however. Please report any bugs for the same on http://bugs.kde.org/.
13 Jun 2017
We have liftoff!
Cue me trying to not get my fingers cut off
The quadcopter has been built! I had some problems during the building process, so this is a guide which will hopefully make things easier for people to start off with making their own quadcopters.
I suggest going through all these websites thoroughly before purchasing a single part for your quadcopter. It’s not an extensive list, so I’ll keep updating it as I find more useful links:
If you live in India, the following sites are good places for shopping for parts:
RCBazaar and RCDhamaka have stores in Bangalore. Robu.in is based in Pune.
Hardware Assembly
For clarity, the components I have used in my build are:
- 1045 Propellers x4
- REES52 DJI F450 Frame
- REES52 CC3D F1 Flight Computer
- REES52 1000KV A2212 30A Brushless Motor x4
- REES52 SimonK 30A Electronic Speed Controllers x4
- APM 4-axis Power Distribution Board Type-B1
- SunRobotics 2200mAh 3S 35C LiPo Battery
- FlySky FSCT6B Computer Transmitter
Most of these parts can be picked straight off Amazon. REES52 has a good bundle for a pair of propellers, 1000 KV motor, and ESC which I would recommend buying to keep costs low.
Frame
The first thing you would want to do is start off with the frame of the quadcopter. If you go for a DJI F450 frame (or one of its hundred clones), you will get a box with four arms (technically called booms) for mounting the motors and ESCs, a base which doubles as a power distribution board, and a board to hold the top of the copter together. It’s pretty simple to set up and all you need is two Allen keys to screw everything together.
I suggest labeling each boom with a number and the direction in which its motor is supposed to spin. The below diagram is a good starting point:
Speaking about labeling, label everything. It only takes a few seconds and it can save many hours of frustration later on. Of note, is the handedness (is there a better term?) of the propeller. Left-handed propellers turn anticlockwise and right-handed propellers turn clockwise. Mounting a propeller the wrong way will cause it to produce thrust in the opposite direction.
Motors
Once you’ve setup the frame, the next thing you should do is take a look at the motors. These motors are brushlessmotors and they are very different from brushed motors. For starters they have three wires instead of the two on brushed motors. Another peculiarity about these motors is that they are out-runner motors. This means that the case of the motor rotates with the propeller and not the motor shaft alone.
Despite being a lot more power efficient than brushed motors, these motors can generate a great deal of heat when running at full power. I would not recommend testing it at full power on the ground as there won’t be any airflow to cool the motor down. This can permenantly damage your motor, and if you’re unlucky, your ESC as well.
Anyway, the motors can be screwed directly into the booms of the quadcopter. Most motors come with a few accessories - an adapter for the base to mount it on to differently keyed frames and a propeller shaft with a nose tip. Don’t worry if the propeller shaft seems to wobble or come loose. It’s designed to only be fully secured when the propellers are mounted on the motor.
The direction of rotation is determined by the ESC, so we don’t need to worry about that at the moment.
Electronic Speed Controllers (ESCs)
The ESCs link the flight computer (FC) with the motors. The input to the ESC is PWM fed over the BEC connector. Each ESC have its own 8-bit SoC to send signals to the brushless motor to turn at the desired RPM. In the FC settings, you can adjust the ESC update frequency, which is usually between 50Hz and 490Hz.
A brief digression on the BEC - the thinner wires at the power input side of the ESC. Known as the Battery Eliminator Circuit, it steps down the voltage of the battery to a comfortable 5V for powering components such as the FC or any other devices you may want to connect to the aircraft. The FC only needs power from one BEC and it may even be harmful to connect more than one BEC to the FC. There are some suggestions here on how to take care of this problem.
The ESCs regulate the amount of power going to the motor depending on throttle input and can get very hot as well. Mounting the ESCs under the booms will give it sufficient airflow to cool down properly. You want to make sure that the three wires with female bullet connectors is facing the male bullet connectors of the motor. The other side with the male connector and the BEC goes to the power distribution board of the quadcopter.
Mount the ESCs on to the booms with rubber bands, or better, zip-ties.
As with all electronics with large capacitors, ESCs can have spectacular explosions when things go wrong. Short circuits or using the wrong polarity on the power input side of the ESC can cause it to get damaged in a matter of seconds.
On the other hand, things are a lot more flexible on the power output side of the ESC. It is possible to connect the three output connectors in any order to the motor, but a good rule of thumb is to connect the middle wire of the ESC to the ground wire of the motor and to interchange the other two wires to reverse the direction of rotation.
Power Distribution Board
The frame of your quadcopter probably will have a power distribution board of its own with solder points. However, I used a separate power distribution board with the T-type connectors for the ESCs and the battery. It also has ports for the BECs and corresponding signal wires with a single 5V DC output.
This went right under the base of the quadcopter. It’s a bit of tight fit to get all the ESC wires under the base. Again, use zip-ties to secure it to the base.
The ground clearance is quite low with the power distribution board attached. You can buy a landing gear or make your own to increase this.
I made a DIY landing gear for my own quadcopter using a badminton shuttlecock tube. It absorbs shocks nicely and gives me just enough ground clearance to mount more components.
Flight Computer and Battery
Now for the good stuff, go ahead and mount the CC3D on the top frame of the quadcopter. Most CC3D’s will come with some plastic adapters and a sticky sheet to stick the CC3D on the quadcopter frame. Take note of the arrow on the CC3D and make sure it is facing the direction in which you want your quadcopter to fly forward. Make sure you leave enough room for keeping the mini USB port and the servo header pins accessible!
After binding the transmitter to the receiver, plug it into the receiver port of the CC3D. If you use the FlySky CT6B transmitter/receiver, the receiver probably won’t work when directly connected to the CC3D on USB power. If so, you can use an Arduino’s 5V and GND to power the receiver for testing it. When flying the quadcopter on Li-Po power, the CC3D will be powered by the ESC BECs which will give it enough headroom to power the receiver.
The receiver can be mounted pretty much anywhere as it is quite small. I mounted the receiver on my quadcopter’s boom.
The final step is to add the Li-Po battery to the frame. Some prefer to mount the battery to the base of the quadcopter, but I found mounting the battery right under the top frame (under the CC3D) from E-W was much better for the quadcopter’s stability. My guess is that this keeps the vertical CoG of the aircraft closer to the line of application of force, reducing the torque when it makes a maneuver.
Again, the place where you mount your battery is dependent on the size of the battery. Secure the battery with as many zip-ties as you want. There’s no such thing as using too many zip-ties to secure components on quadcopters.
Putting It Together
ESC Calibration
Before you start configuring your CC3D, it’s a good idea to make sure your sure your ESC and motors are working properly. For this, connect the ESC directly to the battery and the ESC’s BEC straight into the 3rd channel (the throttle channel ) of your receiver. Keep the transmitter switched on with zero throttle input. On connecting the battery, you will hear a calibration beep from the motor. Put the throttle to max power and hold till you hear another calibration beep. After bringing the throttle back to zero input, you should now be able to drive the motor by varying the throttle input.
In case the motor spins the wrong way, just swap the red and yellow wires of the motor.
Cable Management
This isn’t really cable management, but I couldn’t think of a better title for this section 😅
Connect the ESCs’ BECs to the CC3D. The order will have to be changed later when setting up the CC3D so don’t worry about that for now. I looped the cables through the holes in the top of the frame so they weren’t hanging off the side of the quadcopter. The white wire should face upwards.
The receiver is quite straightforward to setup. The first cable has three leads, one for signal and two for power. This will go in the Channel 1 input of the receiver. The rest of the cables have only one signal lead. Just connect this in the order to which it is connected on the the receiver port side of the leads.
The male connectors for the ESC can go right into the power distribution board.
Software Configuration
The CC3D is a nifty micro-controller. It can be flashed with different FC firmwares and can be extended with GPS and Telemetry capabilities. For now, we will work on a much more humble task - flashing it with a FC firmware.
As the CC3D has been around for a while, it has a good amount of community support in terms of open-source FC firmwares. Two popular ones are Cleanflight and LibrePilot, built out of the ashes of the now defunct OpenPilot.
The firmware gives the CC3D brains to control the aircraft and make decisions on the accelerometer and gyroscope readings. It has a sophisticated PID algorithm to do so.
Both firmwares come with cross-platform desktop apps for configuring the FC. Cleanflight uses a shiny Chrome web-app and LibrePilot has a more traditional Qt desktop app. I liked Cleanflight at first, but flashing it on the CC3D is a mess and I couldn’t get it to work properly. On the other hand, LibrePilot is a joy to flash on the CC3D. The desktop app even auto-updates the CC3D’s firmware if it is out of date. Therefore, being unable to flash Cleanflight, I setup the quadcopter in LibrePilot instead.
LibrePilot has a pretty easy ‘Vehicle Setup Wizard’ which, if followed correctly, will get your quadcopter to airworthy shape 95% of the time. You would want to keep the props off during the whole procedure, especially during ESC calibration.
Following this, you can mount the propellers by selecting the right adapter from the adapter kit each prop comes with it. Stick it in to the reverse side of the propeller and mount the propeller such that the side with the pitch and diameter printed on it is facing upwards. You can then mount the nose tip which comes with the motor with a thin screwdriver or Allen key. All the thrust of the quadcopter is generated from the propellers, so you’ll want to make sure that this is quite tight. This should make the propeller shaft impossible to pull upwards, and if it isn’t, you would want to return the motor before you have a catastrophic accident. The last thing you want is a propeller disloding itself from your quadcopter midflight.
Fly!
Or at least try to if you’re a beginner :P If you’re using LibrePilot, the default setting has stability assist which makes flying easier. For the more experienced (or gung ho) type of pilot, you can change the settings to use Rate/Acro mode to get full manual control of the aircraft.
Another thing worth looking at is tuning the PID values of the FC for better performance. However, LibrePilot’s default values are good enough so this isn’t necessary.
And that’s it for this tutorial. I’ll be writing more as I get more experienced with flying my quadcopter.
09 Jun 2017
I had written this article a bit more than a year ago for a college magazine. This topic has been done to death in a Q/A format, so if you’re looking for something new about Y2038, you probably won’t find it here
Time has always been a finicky thing to deal with. Our perception of time without any stimulus is limited to less than an hour. We would be severely crippled without our abundance of electronic devices synchronized by internet atomic clocks. Unfortunately, these electronic devices on which we’re so reliant on are heading towards a time based computer disaster on the same scale as the Y2K bug of this millennium - known as the Y2038 problem.
How do computers measure time and what is the Y2038 bug?
All UNIX derivative systems (including your iPhone or Android smartphone) measure time by counting the number of milliseconds that have elapsed from the 00:00 UTC, 1 January 1970. This day and time is known as the UNIX epoch. While this method of measuring time has served us well for a number of years, it faces a severe limitation - the time_t int variable (an int variable is a part of a program used to hold integral values) in UNIX used to store the number of milliseconds from the epoch is only a 32-bit data type on older 32-bit computers. This means the time_t variable can only store up to 231 - 1 milliseconds before the counter overflows.
Note: 32-bit systems can hold a 64-bit int by splitting it into two words each of length 32-bits. However, the default int size on 32-bit systems is only 32-bits and a 64-bit int has to be coded separately.
So how long is it between before this overflow?
Exactly 231 - 1 milliseconds after 00:00 UTC, 1 January 1970, which is 03:14:07 UTC, 19 January 2038.
So what will happen?
The overflow in the integer value will cause time_t to reset to - (231) milliseconds. This date is 20:45 UTC, December 1901. This is actually a much more serious situation than just your computer showing a funny date. This has disastrous consequences for systems with 32-bit CPUs as BIOS software, file systems, databases, network security certificates and a wide variety embedded hardware will fail to work. With huge critical machinery such as old electrical power stations controlled by a 32-bit computer, an unmitigated catastrophe is unavoidable.
Oh no! Does that mean my laptop and smartphone will stop working as well?
Depends. The 32-bit time_t variable has been deprecated and replaced by a 64-bit time_t variable which will tide us over for the next 2 billion years. 64-bit CPUs are the standard nowadays and most computers running a 64-bit OS on a 64-bit CPU will not face any such consequences from the Y2038 bug as they use the 64-bit length time_t variable. However, smartphones have only recently shifted to a 64-bit process and 32-bit smartphones and computers will be affected if they are not coded for the 64-bit int length. That is of course, only if you are still using it after 23 years from today :P
But how did this even happen? Why couldn’t we just use a 64-bit time_t variable in the first place? It’s only 4 bytes bigger!
Short answer: Legacy.
Long answer: The UNIX kernel was created in AT&T and Bell labs in the 1970s. There were many competent programmers working on the project such as Dennis Ritchie of C fame. Initially, Bell engineers used a different method for calculating time, but they found that the counter would only work for 2.5 years. As UNIX was planned to be a long project, they changed the time counter to a 4-byte integer. This of course was also limited to a very finite amount of time. However in the 1970s, the consensus was that computers weren’t going to stick around for that much longer and a 60-odd year window was “good enough”.
Couldn’t they just have just used a 64-byte int anyway?
Not really. Computer resources were scarce in the 1970s and 8-bytes of memory to store time_t was more memory than what engineers were willing to give.
Wait a second! Why doesn’t time_t use the unsigned int? Surely UNIX wasn’t programmed expecting us to go back in time!
The time_t variable uses the signed int to account for dates before the UNIX epoch. Dates before 1 January, 1970 are represented in a negative number of milliseconds which is why an overflow would take the computer’s date to 1901.
But this is 2017! Can’t we just upgrade the time_t variable to 64-bits?
Yes we can. In all new software and 64-bit operating systems, the time_t variable has been changed to 8-bytes. The problem is that all legacy software compiled with other older compilers may be incompatible for recompiling with a newer compiler for an 8-byte int value. The problem doesn’t just stop there. Many embedded systems and microcontrollers (including the popular Arduino ATMega based platform) use 16-bit CPUs which simply cannot support an 8-byte integer in a 2-byte word length. Some hardware applications may use proprietary firmware which won’t receive updates.
How can we fix the Y2038 problem?
There isn’t any one-solution-fits-all approach for this since it affects several computer architectures, hardware, and software. While it might be easier to just upgrade all old computers with new 64-bit capable ones, there are still many areas where old 32-bit code is still prevalent. Furthermore, the cost of upgrading all the computer hardware is just too exorbitant to be covered.
If we look at the lessons learned from the past, the Y2K bug was rectified because of the media hype pressuring businesses to update their software to accommodate 4-digit years. Although the Y2038 bug is much more critical and harder to understand than the Y2K bug, there is hope that the same pressure will bring change.
But for now, only time will tell.
Credits: xkcd