Building a Raspberry Pi based Twitter Display

History

One of the first projects I found when I first started playing around with the raspberry pi was a two way Portal mirror. This used a simple display + camera to show a remote location of another “paired” device. This got me thinking about other small frame-based uses for a micro-computer. I realized that there were a few projects for turning a raspberry pi into a picture frame, and I wanted to do something similiar.

Research

The first challenge I had was exploring solutions for displaying text cleanly at potentially low resolution on a raspberry pi. I had previously explored running an X session and chrome browser for a dashboard I built for work. This had some flaws, specifically the results often ran out of memory, it took a lot of heavy processes and a window manager for what really didn’t require it. I started to explore instead ways to use the framebuffer without a lot of heavy graphics work. From there I found the Pygame library and some tutorials that showed easy usage of the framebuffer for displaying text. Perfect!

Design

### Graphics The end result is a gutted Pygame class that instantiates a empty rectagle based on the framebuffer size. We then grab some text to render, word wrap it as appropriate and display on the screen.

Network

I ended up wanting to make the program show it’s ip address on startup so we could address the device if there was any problms. At first I wrote a function that would grab specifically the ip address of eth0. When I expanded the device to use a wifi adapter this solution fell apart. I found another solution that instead tells the code to use the networking stack to connect to a public address and then grabs the local results of that socket connection. This appears to more dynamically grab the RIGHT adapter.

Twitter

I explored the python-twitter module. This was really straight forward to do searches and parse the results. There are so many options for twitter libraries, I can’t say this one is the best but it worked well for my needs. I think when this fails is where my code is missing the most exception handling. If I look up a twitter user and it doesn’t exist, I’m not catching and handling that situation yet.

Results

The end result is this small display that sits on my desk, every 30 seconds it displays a new ‘tweet’, altering the color and source from a yaml list thats pulled in on load. I’ve attempted to have it often re-read the yaml file but I don’t know that it’s working. Auto-reloading the configuration file seemed like a easy way to allow dynamic updates. I also considered polling from a twitter account, but that doesn’t work for topics only for users to follow. I could possibly change it to search for the results of a tweet as if it was a topic, and the users followed by an account for users to follow, although removing topics would not be straightforward. Dynamic configuration data seems to be the biggest challenge with the display. I also considered setting up a small torando server that you could post an api request to for configuration changes. But I don’t think thats actually easier than the current method where I can do a git pull.



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Published

20 January 2015

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