Stavros' Stuff

Angry rants of programming and other things.

iRotary - Part Three

Phone slam 3: The slammening

In part two of project iRotary, we actually got the phone to make calls, but we couldn’t talk or hear the other person. In this part, I promised you some hardcore microphone-to-headset action, and that’s exactly what I won’t deliver!

Instead, what I did was to procure the gorgeous phone you saw in the previous posts. That’s right! All this series so far has been a ruse! I didn’t have that phone to start with, I didn’t have it at all!

However, I do have it now, and I managed to enclose the Arduino in the actual phone. Let’s see how that happened.

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iRotary - Part Two

Working towards a phone I can slam

In part one of project iRotary, we got the Arduino to detect pulses from a rotary dial and turn them into a phone number, all in the name of turning this phone:

into a mobile phone I can use on the go. In part two, we will actually connect the Arduino to a GSM shield and place calls with the rotary dial like it’s 1993. I have seen the future, and it is the past. Read on for details!

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iRotary - Part One

Finally, a phone I can slam again!

Lately, my mobile phone (an HTC One) has become very slow. I think it’s mainly SwiftKey, which is slow like dog, but no matter. As a good consumerist, I must purchase a new phone. However, I am also an angry person, and I sorely miss the tactile sensation of slamming the phone on someone’s face.

Because of this, I decided to put my engineering degree to good use, and went out and bought a phone. Thus begins project iRotary, which aims to turn this:

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Netflix for the rest of us

OMG Netflix in Greece!

If you’re nothing like me, you watch a lot of shows and movies, which means you must have heard of the wonder that is Netflix. Tens of movies and shows, all ready to stream in high definition at a moment’s notice for a very cheap monthly fee, what’s not to love? Well, apart from the MPAA not letting them have a larger selection, and the MPAA not letting them work outside the US, not much!

There’s a bunch of services like Netflix that don’t work outside the US, which is an affront to my human rights and sense of entitlement, so I took it upon myself to make watching Netflix and listening to Pandora just a bit easier. To this end, I created a

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Calling single-argument methods in Django templates

No longer are your methods confined to bare calls!

One of my pet peeves when it comes to Django is that you can’t call methods that require arguments in templates. While this is fine most of the time, it does mean that you need to have one property or method per call you want to make, which sometimes gets very cumbersome.

I needed a way to define various dynamic permissions that are calculated at runtime (for irrelevant reasons, Django’s permissions framework wasn’t a good fit), and writing properties like can_register, can_add_tags, can_subscribe got tedious. These tended to be defined all over the place, rather than in one central spot, and it was hard to add more checks without cluttering the classes.

I would much prefer to have a single method (let’s call it can()) that accepted a string with the permission I wanted to check, and return True or False, depending. This is easy to do in the views, but templates would never be able to call it with an argument.

However, since Django can do dictionary-style attribute lookups, I could add a dictionary interface over the method, and allow

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Get a text when there's motion in your house

Who needs friends when you have an Arduino?

Like every person, I have a burning desire to know who’s in my house when I’m not. A few months ago, I decided that I had had enough of the uncertainty of my extradomicilial activities, and that I needed to do something about it. I realized that I had two options. The first option would be to hire someone to be in my house 24/7, but that would get a bit embarrassing when I wanted to watch reruns of Desperate Housewives. The other option would be a motion sensor that texts me when it detects motion.

Luckily, this proved really easy to do with an Arduino. All I needed to get was

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How to safely store your bitcoins

Keep your money close and your bitcoins closer

Let me tell you a story about how this fool and his money were soon parted. About a year ago, I added Bitcoin payments to Dead Man’s Switch, because it seems that people who want to send messages after their death are also the sort of people who don’t like using actual money.

One or two people decided to use that payment method, probably mostly because it was the only thing they could buy with their newly-mined bitcoins, and I was the proud owner of a whole bitcoin, worth about $20 at the time. However, storing it was a bit of a problem, as I would either have to trust a third party with it or use the official client, and store the entire multi-gigabyte blockchain on my computer.

You can probably see where this is going. I didn’t want to store a bunch of gigabytes for $20, so I left my coins on

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I found the Holy Grail of backups

Finally, encrypted, fast offsite backups

If you’ve been reading my ramblings for a while, you will remember that I have been looking for a good way to back up my files, without much luck. My requirements are:

  • Encrypted (on the original machine).
  • Fast/bandwidth-efficient (deduplication is a plus).
  • Open-source.
  • Cheap.

My files are mostly code and photos, which aren’t really critical (the critical files are stored in repositories and multiple computers), but losing all my photos wouldn’t be too great. That’s why any backup solution I wanted had to be cheap enough to justify the cost.

Every single piece of software I have ever tried fails in at least one of the above. I currently use SpiderOak, which is everything except open-source, so that fails too.

However, my quest is finally over. I have discovered the Holy Grail of backups, and its name is

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Arduino-powered irrigation system

Control your field’s irrigation system with your mobile

A few weeks ago, I was showing my dad my latest project, the Arduino RF remote control, and he lamented the fact that I still hadn’t made an irrigation system remote control for him. We have a few acres of fields that need irrigation, which is done with a system of pipes from a central water pump. At that point, however, the fact that he needed a remote control for the pump was as news to me as it is to you, so I asked him what he needed exactly.

He told me he needed a system that would allow him to call or text a phone number and turn the pump on and off remotely, as well as something that would text him if there was a problem that

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Mozilla Persona accounts with disposable email addresses

Mozilla Persona, now with extra disposable email address

If you follow the news, you’ve hopefully heard of Mozilla Persona, the wonderful new way of centralizing logins on the web. In a nutshell, Mozilla Persona works the same way as the “log in with Facebook” you see on many sites, except that, instead of Facebook, you use your email account to log in. The great thing is that sites never have your password, and you only need to have one password for every site on the web (Persona uses your email address as your username).

One downside of the default implementation is that you have one account per email on the default bridge (this isn’t strictly true, but adding more accounts is cumbersome and not meant to be done for every site). This is a problem for me, as I use the excellent 33mail service to create disposable email addresses for every site I visit.

Fortunately, there is a way to use disposable email addresses as usernames on Persona. Here’s how:

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