Author Archive

My pull request was rejected… and I loved it.

Monday, 28 September 2015

Back in the day when A-stad (the project I’m currently working on) was born, there were no tests, hardly any code reviews and in the end we were happy if it worked at all.

Though that did seem a good idea at the start (boy, were we fast) rather soon than late we were confronted with reality. Coding like that doesn’t last long, in no time bugs were appearing everywhere and our time was devoted to fixing bugs more than it was to writing new features.
This had to change.

Simple enough… in theory.

“Just” review code, write unit- and functional tests and automate everything. We knew the theory but change came at (quite a) slow pace. Turns out changing habbits is hard. Very hard.

Fast forward 2 years, where our code gets reviewed en our tests run before any pull request is merged into the development branch.

Last week my pull request was rejected. Twice. And at that very moment I was incredibly proud of what we had achieved. Not only are tests a must in new (and changed) code, but code is actually reviewed (instead of merging it after looking at it for a minute), code coverage is important and discussions arise on how we could improve those 10 lines of code into 4 more efficient ones.

At this point I have only one thing to say: well done devs. Well done… 😎

Build your own drone (pt 7) – Reflection

Sunday, 11 October 2015


Why in the heck would you build a drone?

It’s incredibly fun to build your own drone, but you won’t be able to get it to fly right away. If you’re planning on squeezing in some airtime the same weekend you buy it, you’re better off getting a ready-made one.
But here is my 2 cents: the pleasure of seeing the drone you build with your own 2 hands, flying up in the air, is priceless.

It’s fantastic that you get to choose all the components yourself. Want heavier motors? No problem, just install them! Broke an arm off your frame? Don’t sweat it, get spare parts.

So what did building my own drone cost me?

You mean except from the pounds of chocolate I had to buy to bribe my girlfriend into spending the weekend with me, testflying the drone?

Not too much, in my opinion. Below you’ll find a list in which I tried to sum up all the things I used. Of course it doesn’t contain everything: materials, delivery fees, wrongly orderded pieces, … have all been excluded from the list.

Keep in mind that this is just a start. I’ve been working on my drone and adding/changing parts on the go. (e.g. I installed a new Flight Controller.)

Anyway, about that list:

Description Total
Frame 17,03 EUR
Motors 55,72 EUR
ESC’s 31,64 EUR
Flight Controller 19,44 EUR
Sender and receiver 119,47 EUR
Power 68,97 EUR
Total 312,27 EUR

A more detailed view.

1) Frame

Amount Description p/p Total
1x Hobbyking SK450 Glass Fiber Quadcopter Frame 450mm 17,03 EUR 17,03 EUR

2) Motors

Amount Description p/p Total
4x Motor
NTM Prop Drive Series
12,26 EUR 49,04 EUR
4x NTM Prop Drive 28 Series Accessory Pack 1,67 EUR 6,68 EUR

3) ESC’s

Amount Description p/p Total
1x Power Distribution Board 1,61 EUR 1,61 EUR
2x PolyMax 3.5mm Gold Connectors 1,45 EUR 2,90 EUR
4x ESC’s 5,99 EUR 23,96 EUR
1x HXT 4mm to XT-60 Battery Adapter 2,50 EUR 2,50 EUR
1m 1m heat shrink (black) 0,67 EUR 0,67 EUR

4) Flight controller

5) Sender and receiver

Amount Description p/p Total
1x Turnigy 9XR Transmitter Mode 2 61,29 EUR 61,29 EUR
1x Turnigy 9XR Safety Protected 11.1v (3s) 2200mAh 1.5C Transmitter Pack 12,80 EUR 12,80 EUR
1x 10CM Male to Male Servo Lead (JR) 26AWG 1,34 EUR 1,34 EUR
1x FrSky DF 2.4Ghz Combo Pack for JR w/ Module & RX 44,04 EUR 44,04 EUR

6) Power

Amount Description p/p Total
1x Turnigy 3300mAh 3S 30C Lipo Pack 24,60 EUR 24,60 EUR
1x Lithium Polymer Charge Pack 25x33cm JUMBO Sack 2,40 EUR 2,40 EUR
1x HobbyKing™ Lipoly Low Voltage Alarm (2s~4s) 2,54 EUR 2,54 EUR
1x Turnigy Accucel-6 50W 6A Balancer/Charger w/ accessories 35,19 EUR 35,19 EUR
1x HXT 4mm to XT-60 Battery Adapter 2,84 EUR 2,84 EUR
1x Turnigy Battery Strap 330mm 1,40 EUR 1,40 EUR

Build your own drone (part 6) – The power supply

Monday, 4 January 2016

Sadly, a drone is not completely magical. It still needs energy to fly.

What seemed really simple at first (connect a battery, click your heels 3 times and voilà: a flying drone), turned out to be one of the most difficult steps in this whole proces for me.

Apparently, Lithium Polymer (LiPo) batteries don’t work in the same way as the small AA-batteries from your standard remote control. Bummer.

What you’ll need

Amount Description Price Total
1x Turnigy 3300mAh 3S 30C Lipo Pack 24,60 EUR 24,60 EUR
1x Lithium Polymer Charge Pack 25x33cm JUMBO Sack 2,40 EUR 2,40 EUR
1x HobbyKing™ Lipoly Low Voltage Alarm (2s~4s) 2,54 EUR 2,54 EUR
1x Turnigy Accucel-6 50W 6A Balancer/Charger w/ accessories 35,19 EUR 35,19 EUR
1x HXT 4mm to XT-60 Battery Adapter 2,84 EUR 2,84 EUR
1x Turnigy Battery Strap 330mm 1,40 EUR 1,40 EUR

The battery


Caution! LiPo batteries are dangerous. As with everything: make sure you are properly informed before using them.

Low voltage alarm

The first thing I learned about AA-batteries as a kid, was that it’s ok if you use them so much that they end up dead. The fact that that mostly happens right in the middle of your game, is a whole other issue*.
(*frustration talking here).

The first thing I learned about LiPo batteries, is that you can not let them die. Turns out LiPo batteries aren’t rechargeable once they are drained completely. Should that happen to you, say goodbye because they’re ripe for the bin.
(Yes, there are ways to try and recharge them once they’ve died and yes, I tried that out, but no, none of those tactics are really safe.)

Low voltage alarm

By the way, to avoid your batteries from dying on you mid air, causing your drone to ‘fly’ to the ground at 9,81 m/s2 , it’s of paramount importance (look at me using fancy words) to figure out when your battery is almost dead.


Therefor, let me introduce you to the Low Voltage Alarm. An investment of a whopping 2,54 EUR that will prove to be a sound one. (Ever seen a drone hit someone in the head, when there’s nothing you can do? Neither have I and I intend to keep it that way. My drone missed my girlfriend by a hair and I ‘m still hearing about it. )

How to recharge

Got a handy-dandy standard battery charger lying around? Good for you, but you won’t be able to use it for this project I’m afraid.

You’ll actually need quite a lot of equipment and not only to simply recharge the battery:
Turnigy 3000 mah, lader en save bag

The grey bag on the left of the picture is a safety bag. By now, you’ve learned that LiPo batteries are not that safe and that they can easily catch fire. Should that happen, send me a card and thank me for advising you to buy (and use!) this bag. I’d also advice you to hang around while recharging this type of battery so you can keep an eye out for a sudden swelling. (Hint: a swollen battery is bad, bad news.)


So: put your entire battery, except for the two wires, inside the bag. Then, connect one wire to the HXT 4mm to XT-60 Battery Adapter and the other wire to the battery charger (with supplied wires).

By the way, that battery charger comes without power supply, so you might want to provide a 12V power supply for that.

Once you’ve got everything plugged in, set your battery charger to LiPo. In addition to that, make sure the number of cells on the battery and the charger are the same (THIS IS IMPORTANT) and start your balanced charge.

Now for the good news and the bad news.

Good news: once your battery is charged, nothing stops you from flying to your hearts content (or at least until the battery decides it’s done for the day).
Bad news: just because the battery stopped working, doesn’t mean you’re off the clock.

Once you’re done flying, you can’t just put away said battery. You’ll have to reconnect it to the charger that you’ll set on ‘storage’. Once that proces is done, you can disconnect your battery, put it away, grab a beer and be damn proud of yourself.

How to fasten a battery

‘Minor detail’ once you’re flying is that you’ll probably want your battery to hang on there tightly; seeing how you want to be able to control your drone (Believe me, pissed off girlfriends are no joke).
I started of using cable ties but it unnerved me that I had to throw them away after each use.
My go to methode became a sturdy velcro strap but any kind of strong velcro will do.

Once the battery is securely attached, you can connect it to the wire we made in this blogpost.

Now, and only now, click your heels 3 times and voilà: let there be power!

The power of books

Wednesday, 27 January 2016

When I learn a new HOTNEWTHING the first thing I usually do goes as follows: I grab my computer, search for HOTNEWTHING en read some pages online.
Then I look (or ask) for a good tutorial for HOTNEWTHING and follow along.
Most of the time I have something working in HOTNEWTHING at the end of the day.

But do I truly understand it?
No. Not at all.

Last Christmas holiday a colleague lent me some books he had reviewed. I was determined to read them during the holiday so I could give them back the day I returned.

Admittedly, I struggled reading them on paper. I found it to be very slow paced; no distractions at all and no link-after-link-after-link I could click because: “Ooh, that’s interesting too”. After years of learning on the internet only, this was a whole new experience.

And a good one. I learned more in depth about nodejs/javascript after reading those three books than I did in the months where I googled.

Secure your Pi

Tuesday, 10 May 2016

I’ve been trough this way too many times. So here’s a note (mainly for myself) so you and I know what to do when connecting a Raspberry Pi to the web.

Create a new user

This (low-privileged) user is needed so we don’t need to use our root user to login or run applications (because the amount of rights the latter has is plain dangerous).

You can do that with: sudo adduser username Needless to say  you’ll want to change ‘username’ to a username you’d like to use.

Enable key based authentication

Well, this part is explained way better than I ever could on the Raspberry Pi website.

Disable root login over ssh

Now that we have a new user which we can use to login over ssh (tried and tested, right?), we can disable our root login over ssh.
To accomplish this you’ll need to change the /etc/ssh/sshd_config file.

run: vim /etc/ssh/sshd_config

and make sure this is in your configuration file:

PasswordAuthentication no
PermitRootLogin no

Change it if it exists or add it if it doesn’t.
After your changes you’ll need to reload ssh:

/etc/init.d/ssh reload

Please be aware that this only covers the bare basics and you could (and should) do way more to secure your Pi.

Mounting WD My Cloud on Ubuntu

Saturday, 29 June 2019

After the january firmware update (2.12.127) I couldn’t mount my Western Digital My Cloud anymore. I took a look at the release notes and sure enough “security was improved“.
That’s probably the reason I got a “mount: /media/NAS: mount(2) system call failed: Connection refused.” everytime I tried to mount the My Cloud.

What they didn’t mention was how to fix this. Luckily it’s not that hard.

On your My Cloud

My cloud needs to know who can access the drive and who can not.
Log in on your My Cloud via ssh and edit the exports file:

vi /etc/exports

if Public is the folder you want to mount, just add:

/nfs/Public *(rw,all_squash,sync,no_subtree_check,insecure,crossmnt,anonuid=65534,anongid=1000)

Note that I added a * here which means everyone has access. You should add the ip-address of the client instead.
After this run

sudo service nfs-kernel-server nfs-mountd restart 
sudo service nfs restart

On your computer

At this point you should be able to mount your My Cloud again

sudo mount -t nfs MYCLOUD_IP:/nfs/Public /media/NAS/