Stavros' Stuff

Angry rants of programming and other things.

How to remotely control RF devices with the Raspberry Pi

The RF transmitter/receiver pair

After my wildly successful post How to turn your Raspberry Pi into an infrared remote control, which was mainly a list of various resources and instructions on how to record and replay infrared signals with the Raspberry Pi, I am writing the second instalment, on controlling RF devices with it.

I’ve long wanted to control my garage door from the internet (because apparently I love making useless enhancements to things that run on electricity), but I couldn’t figure out the codes it sends. Even though I could, in theory, use the Raspberry Pi as a poor man’s RF transmitter (hint: don’t do this because of the noise, and it doesn’t work anyway because of kernel timings), I didn’t know what to transmit with it, and I couldn’t find the protocols anywhere online.

To help in this herculean task, I bought an RF transmitter/receiver pair (pictured on the right) from eBay for around 1 euro (with shipping), which can decode received signals (and send them again).

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How to turn your Raspberry Pi into an infrared remote control

A few months ago, I bought a Raspberry Pi, and it’s been the best recent purchase I made, by far. Not so much because I have that many things to do with it, but because it features a few GPIO pins, which you can control with software and make output ones and zeroes (basically high and low voltage).

This has opened a whole new world to me, as, before this, software and hardware were completely sep

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An example of provisioning and deployment with Ansible

It has recently come to my attention that many people don’t use virtual machines for development, instead polluting their system with various dependencies and making life harder for themselves. Unfortunately, even the people who do use VMs for development often perform provisioning and updates by hand, thus ending up with slightly different configurations for development, testing and production, which often leads to uncaught bugs on production.

In this post, I will not only attempt to detail some best practices I’ve learned, but I will also list provisioning and deployment configurations that will make this a one-command process.

The easiest way to do repeatable deployments is to create scripts which will handle everything for you. By the end of this post, you will be able to get from a new installation to a complete Django/postgres/gunicorn/redis stack running (and accepting users) with one command.

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Better password reset procedures

In the past few months, we’ve seen a series of high-profile account breaches that gave control of users’ accounts to malicious thieves. I’m sure many will remember the Matt Honan hack, where an attacker was able to gain access to the journalist’s accounts and wipe his devices by fooling Apple support into resetting his password for them.

More recently, Skype proved to be vulnerable to the same attack, which is really bad news for password resets in general, because there’s really no good way for someone to guard against this. If you haven’t specified an email address (or if you forgot the password for your email address), how can a provider authenticate you? They will have to use security questions, or information about your account, or other ways of doing it.

Security questions are usually very low entropy, much lower than the actual password, and thus they should probably be discouraged. Unfortunately, many services (including banks) use them.

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Monitoring your system's temperatures with Python

I have suddenly noticed that my computer’s fans have been more noisy than when I first bought it, and now it’s driving me crazy. I wondered if I could cut the fans’ power without increasing the temperatures inside the case too much, or even leave the case open. To test it, I spent five minutes writing a small script to monitor temperatures in Python, using smartmontools and lm-sensors.

This is that script:

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How to replace a Django model field with a property

If you use Django for your web apps, you will probably have come across a situation where you need to run some custom code on assigning a value to a model field. You’ve probably hacked around this by overriding the save() method or some other arcane hackery, but this is not only unnecessary, but it’s more complicated than it should be.

You can use a Python [property](http://docs.python.org/2/libr

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Proxying two connections in Go

I have recently taken an interest in the Go programming language (or golang, thanks, unsearchable name), and I thought that a fun weekend project would be to write a Postgres connection pooler that didn’t require separate authentication, and just passed through to the database the credentials it got from the client.

Mid-way through the implementation, I realized that this wouldn’t work due to the

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Adding a "login as user" button to the Django admin interface

Working on Instahero these past few days, doing mostly customer development, I’ve frequently needed to log in as a user and see what they see, so I could walk them through using Instahero, troubleshoot issues they were having, or better respond to feedback.

To achieve that, I had written a custom authentication backend that allowed me to log in as any user I needed. T

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Developing an IRC frontend in Go

I’ve recently been considering an idea for a new project, and I’ve slowly began to code it in my spare time, when I’m not developing Instahero. The basic idea is a bot that will hang out in companies’ channels, giving them useful commands, logging, and lots of other functionality.

There are various open-source solutions which one can use to do the same thing, but I think there’s also need for a hosted solution where you can just register, enter your room details and get a bot in it in one minute. As a developer, I know my life would be much easier if we had deployment commands, conversions, various searches, bug report notifications, etc available right in the channel where our team spends the day. I’m sure other developers feel that way too, so I started developing Instabot.

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