That's right; I think I can do one useful project with my Pi in the next ten years.
People go crazy with their Pis: rigging up their microwaves to cook food according to the bar code on it, taking pictures from very very high in the sky, and building souped-up irrigation systems that would be the envy of pot farmers everywhere.
I do have ambitious goals in mind, but I wanted to start with something a little simpler. Some of you may remember my Rube-Goldberg-esque "Radio Broadcast Podcast." An obvious failing of my original setup was that it required me to leave my MacBook running. Predictably, this has turned out to add enough friction that the recordings don't get made.
At the time, commenters offered suggestions to fix that obstacle. One was to set up an EC2 server that could run all the time. A good idea, and I'm certainly comfortable with EC2, but I never got around to it. Between launching a big game and having a baby, the priority on the whole endeavor kept dropping. Still another suggestion was to just buy a server for the home. A very good idea, but we didn't have space for it even before we had a baby.
Enter the Raspberry Pi. Since it's just a normal computer that runs Linux, it can also be a server. Not a super-powerful one, but I don't need a super-powerful server for my house. And it's hard to argue with the physical footprint: the Pi and its case are roughly the same size as two or three stacked decks of cards. I just tucked it into a small space behind our TV.
I decided to start from scratch on my radio-to-podcast scripts, mostly because I wanted to fix some problematic and error-prone behaviors from version 1. It ended up being a few independent parts:
- A Python script runs every five minutes as a cron job and uses a config file to determine if it should be capturing streaming audio. If yes, and streamripper isn't running, it starts the program, figuring out a file name based on parameters in the config file (including adding numbers if a file of that name already exists.)
- Another cron job looks in the download directory for any mp3 files that haven't been touched in 5 minutes, uploads any it finds to S3 via s3cmd, and then deletes them.
- Yet another cron job creates a podcast-compliant XML file by getting a listing of items on S3, running them through an awk script that generates the necessary XML, and then taking that output and uploading it to S3.
This may still seem Rube-Goldbergian, but it's designed to be more resilient than its previous incarnation. If streamripper crashes or the network goes out, my script will ensure that the music starts recording at the next opportunity and it won't overwrite the first part. If the Pi can't get to S3 for some reason, the files will stay in place until needed. There's no cleverness around updating the podcast xml file; it's created from scratch every time. (Note that doing a bucket listing on S3 very much exposes you to eventual consistency issues, but even a day's worth of latency is probably fine for my purposes.)
The onus is still on me to clear old files from S3, but that's something I can do every few months. And once I do, the XML file will reflect that within an hour.
The next step is to run an HTTP server on the Pi so that I can log in and make configuration changes from any of the devices on the network instead of sshing in and modifying the config file directly. And after that? I'm tempted to add AirPlay capability so that if I happen to be home and awake, I can send the current download to the living room speakers.
Overall, I'm pretty impressed with the Pi's capabilities. I doubt I can pile too much onto it, but I'm curious to see what its actual limits are as a household server. Future projects involve using its ability to talk to other electronic components, which is one area where the Pi shines.
* I bought the Maker Shed Starter Kit. It comes with a good book and most of the stuff you'll need to get going and do the book's exercises.