posts tagged with the keyword ‘linux’

2013.09.06

CameraPi

If you wondered why I needed a Raspberry Pi case that could also hold a Raspberry Pi Camera… well, seriously, don’t you people know me by now!? :)

This ‘CameraPi’ is a prototype for Time Lapse Bot 4, and if you’re not familiar with my time lapse hardware experiments, check out the Time Lapse Bot project page for a good introduction.

My Time Lapse Bots have always relied on old computers, and while you can typically get old computers pretty cheap, they are also, well… old. They run old software, they often have hardware failures, non-working batteries, are heavy, and a lot of other things that are (sometimes) fine, but sometimes annoying.

Enter the Raspberry Pi, a small, inexpensive, low-power, modern Linux computer that can use an add-on camera module to create an all-in-one solution to time lapse captures. This is the kind of stuff I love playing with!

So here’s the story of making the CameraPi. I’ll avoid getting into code at this post and just talk about the process and some applications.

At raspberrypi.org I grabbed the NOOBS install, mainly because I wanted to test it out, and it worked well! I went with Rasbian. I think it had all the camera software baked in, but if not, it’s easy to add.

AppleTalk

Once up and running, I added Avahi to give the Raspberry Pi a nice network name (camerapi.local) and I also installed Netatalk to allow my Mac OS X machines to easily connect to it. Neither of these are required for the camera stuff, but I tend to drop these on most Linux machines I use.

As for the image capture, while the camera utilities have some time lapse capabilities, they did not work for me, which is fine, I created my own. (I should note that the Raspberry Pi is for educational use, so I try to follow that idea and, well, learn a lot while using it.)

I wrote a simple bash script to capture a new image every 60 seconds. You can set whatever interval you like, but I like 60 seconds. For one day that gives you 1440 images, if you’re keeping track at home. Depending on your image size and compression settings that could be over 1GB per day of still images. I’m currently using 1280×720 for my image size, as that works well when compiling video.

Photo

As long as we’re capturing images every minute, why not have a way to display them remotely via a web browser? Sure! I also installed Apache for that. There are lighter HTTP servers, but I like Apache. I wrote a simple CGI script to grab the latest image file and display it on a page… and there’s also a link to all the images for the day. Oh, and the page auto-refreshes so it keeps showing the latest image. (The images are named like so: 20130905140427 using the YYYYMMDDHHMMSS format.)

Files

OK, so we now have this running archive of photos. At some point (like, the second day) you’re going to have way more images in that folder than you want. Another shell script is the answer! Script #2 runs after midnight, grabs the date of the previous day, and moves all images matching that date to their own folder. (Oh, where do we store all these images? On a tiny USB thumb drive. It’s an 8GB drive. We figured filling that was better than filling the SD Card that contains the system.)

Files

Now we’ve got a folder named 20130905 with 1440 images in it. We should probably do something with it… Make a video! Once the files are moved we run a command with mencoder to compile all the JPG files (sorted by name, which is also sorted by date) into an AVI file. I don’t really care for AVI files though, so when that is done (and, it takes about 6 hours due to the high-quality encoding settings I use) we then use avconv (which used to be ffmpeg, sort of, oh, Linux!) to convert the AVI to an MP4 file. That does not take hours. This is all messy and could be done better.

Video

So after all that, we now have an MP4 file we can view in our browser, though it’s a silly MP4 that needs to completely load before it starts. Silly! There must be a better way.

Yes. There must be a better way. I’m sure there is. Here’s the thing. I really just started hacking. I didn’t know where I was going, so it’s all been guessing and trying things along the way. That’s the beauty of it. I’m not building this for a client. I’m not building a commercial product. I’m just playing and learning. I love it.

Oh, I forgot, I also set my capture script to launch at startup as a service. That means it also stops cleanly when you halt the system. Also, you can halt the system via another CGI just by loading a web page. Secure? Probably not. Ideally I’d like to be able to have the Pi create a WiFi network I can attach to from my phone and control. That would be nice. I’m sure it’s doable, I just need to dig in more. Dig. In. More.

Well that was fun! Thanks for reading this. If anyone really wants more info on the code, I could clean it up a bit (or not) and post it. As always, improvements are very welcome.

Update: Here’s an example video.

2013.03.05

Linux

Oh Linux… sometimes you make it really hard to love you.

While the recent data rescue went well, other things have not been as easy. Let’s see where we are, shall we?

Home Server
This is the old dead-screen PowerBook that ran for years without issue. Until it had an issue. I rescued the data from it, and then I figured I would do a re-install of Linux on it, but so far it’s been all failure. The external VGA connection doesn’t seem to want to display anything, so without a screen to see the install, I don’t even know if it’s booting up properly. (This is a recurring theme, btw.)

Raspberry Pi
One of my Raspberry Pis occasionally hangs on boot. Sometimes. Other times it works fine. Since it’s headless I needed to attach it to a TV to see this. The other Raspberry Pi I have does have an HDMI-VGA adapter, which works when you edit config.txt properly. Sometimes. And yeah, my RF Modulator to use the composite video seems to have died, so that option was out as well. Also, the SD card cracked. These are all fairly minor things, but they add up.

(New) Xubuntu Laptop
While it’s a new machine to me, it’s a 10 year old laptop running Xubuntu. It was going to be (will be?) my new Lab Computer, controlling the RepRap, and hopefully running Octoprint, which won’t run on the Eee PC I now use to control the RepRap. I left it running with my account logged in and it went offline… kernel panic. Hmmm, let me check right now. Yeah, it’s hosed up. I try to ssh in and get ‘Input/output error’ so something isn’t right. Dammit.

Eee PC
Well, this little beast keeps chugging along. Besides the fact that it can’t do much, it can control the RepRap, and it does a pretty good job of not losing the wifi connection. All good.

Another One
Since I may need a replacement for the old PowerBook that was the Home Server, I figured I’d try an old G4 iMac with a dead display. Multiple attempts with Ubuntu Server and Xubuntu Desktop all failed. Won’t boot from a CD or DVD. I did read about an NVIDIA driver conflict, urgh. I may try some other distros, but I’m thinking it may be an issue with the fact that the built-in display is dead and the external VGA connection isn’t doing the right thing. Bummer.

Keep in mind I’m considered really good at this stuff… but I guess when shit goes wrong, it really goes wrong.

2013.02.20

If you read about my Radio Milwaukee Radio and thought having just one station to listen to was rather silly, we can do something about that.

One station means no choices (and no controls) but with multiple stations we need a way to select which one you want to hear, and there are clients that can make that possible. Since the Raspberry Pi is on our home network via WiFi, that means any other device on the network can control it.

mpd

I first tried MPD-Web-Remote, which looks great on iOS devices, and fine in any WebKit-based browsers, but I’m a Firefox fan, and it looks like total crap in Firefox, so I kept looking…

mpd

I prefer MPD-Webinterface, which looks good in Firefox, and not as great on iOS devices. Of course, since these are just web applications running on the Raspberry Pi you can install as many of them as you like. (You’ll obviously need to have a web server running on your Pi. I dropped Apache on mine along with PHP using the standard apt-get method.)

And since these are PHP web apps, you’ve got the source, and can edit the CSS as you see fit, so customizing the look should be pretty simple.

Want more options? There’s a giant list of MPD clients on the Music Player Daemon Community Wiki.

And hey, if you’re wondering how I got 3 stations listed instead of just one, compare the original code to this code:

#!/bin/bash
 
mpc clear
mpc add http://radiomilwaukee.streamguys.net:80/
mpc add http://129.89.70.253:80/wuwm_1.mp3
mpc add http://75.102.5.99:80/wpr-ideas-mp3-64
mpc play
 

This creates a playlist with 3 items, and will start playing the first item in the list, so put whatever you want as the default first. This list will play the 88.9 Radio Milwaukee stream until you select another one.

mpd

You can even add new streams (temporarily) using the MPD-Webinterface. At the bottom of the interface is a text field, just paste in a stream URL and hit return to add it to the list. (I pasted in http://wmse.msoe.edu:9000 for WMSE 91.7) I said ‘temporarily’ because only the three that are hard-coded in our bash script above will survive a reboot/restart.

Oh, keep in mind you need the actual stream URL, not the playlist URL, which is one that usually ends with a .pls file extension. Normally you’ll need to view the source of a .pls file to see the stream(s) listed within it.

That’s it for now kids… have fun with your Raspberry Pi Radio!

2013.02.20

Rescue Me!

Sometimes it’s hard to believe my adventures with Linux go back nearly 15 years. For the first few years I kept a notebook titled The Road to Linux, which, looking back now, I find mildly entertaining.

I have a history of cobbling together old hardware into working Linux machines, and it wasn’t until 2007 when I actually bought a working Linux laptop. The Eee PC was a tough little machine, and after I got a MacBook Pro I didn’t use it much, until last year when I made it control my RepRap. It’s worked well for that. (The external monitor at home helped quite a bit too.)

I’ve been running a Linux server at home for a long time, and a few years back a friend offered me a broken PowerBook, so I managed to get Ubuntu on it and made than my low-powered Linux home server. It’s worked well, and really had no issues… until I decided to go crazy and run a system update on it. I know, and you know, that backups are important, and you know, and I know, we all still fail to do them properly sometimes.

Well, the system update failed, leaving the system unbootable. And yeah, I had two things on it that I sort of needed. Urgh. Time for some data rescue! I’ve got lots of experience doing data rescue with Macs, but not as much with Linux. Still, it was fairly easy.

Since this was my “home server” and not anything for work, I was probably a bit lax on properly administering it. (I won’t be in the future.) Most of my boxes with databases have cron jobs to dump them to disk every now and then. This one didn’t, and that’s where the fun begins.

I ended up opening the PowerBook and pulling out the drive (thank goodness I’ve got a full set of Torx drivers) and connecting it to the Universal Drive Adapter to turn it into an external USB drive. But what could I connect it too?

As luck would have it, a few months back a relative gave me an old Dell laptop to “wipe clean” and dispose of. I of course dropped Linux onto it. I ended up using Xubuntu, which works well on a 10 year old laptop. Seriously, I do love the ability for Linux to turn old, old, old hardware into something useful.

I plugged the Universal Drive Adapter into the Dell running Xubuntu and copied all the files I needed from the drive. Done. Mostly… except for that one database.

The database rescue took a few more steps. Luckily, I had installed MariaDB onto the laptop. I’ve always used MySQL but in a “what the hell” moment, I decided on MariaDB, which is “an enhanced, drop-in replacement for MySQL.” Indeed it was.

I ended up running a few familiar MySQL commands, first to create an empty database, then to add a user with the proper permissions, and then it was just a matter of copying the correct files from /var/lib/mysql into place from the old drive to the new drive, and bam! My data was all in MySQL, well, in MariaDB.

Just to confirm all was good, I dropped the proper files in /var/www and poked at Apache enough to get my app running and test the database connection. All good.

So now that I’ve got all the data I needed from the PoweBook’s drive, I should probably wipe it and re-install Linux on it. Again. ;)

2013.02.10

Radio Milwaukee Radio

I started working on this project months and months ago, so I should probably share what I’ve got so far… as always, it’s a work in progress.

If you live in Milwaukee and listen to the radio, you’re probably familiar with 88.9 Radio Milwaukee. I’m certainly familiar with it, as it’s a great station, and not just for the music, but for their pieces that spotlight the great things happening in Milwaukee.

Since I don’t actually live in Milwaukee right now, it’s a little difficult to pick up the broadcast at home, but no worries, since they stream it over the Internet, we can use a Raspberry Pi (a cheap single-board computer) to play the stream.

Radio Milwaukee Radio

All we need to do is add some power and some speakers (and a little bit of code) and the Radio Milwaukee Radio is ready to go!

I used this post to figure out how to run a script at system startup. Since the Raspberry Pi runs Linux, I’m comfortable mucking around on the command line via SSH, others might not be, but since the worst thing you can do is destroy the entire system and have to re-load it onto an SD card, the risks are small.

Oh, and here’s the script.

#!/bin/bash

mpc clear
mpc add http://radiomilwaukee.streamguys.net:80/
mpc play

MPD is the Music Player Daemon, which deals with playing the stream, and MPC is the Music Player Client which controls the MPD server. The script tells mpc to clear whatever it’s doing (just in case) and then add the 88.9 stream, and start playing it.

(It’s a bit more complex that just that, as there are some startup services that need to be added, but I still need to clean up that code.)

I’ve seen a lot of complex Raspberry Pi radio streaming projects, and while I’ve also played around with different clients to control things remotely via a browser running on a phone or tablet, I wanted to keep this really simple, and create a single-purpose device that did one thing… play the awesome stuff I hear on Radio Milwaukee.

(I also put together a short video showing it in action.)

Note: I also wrote up a post about laser etching the logo on the Milwaukee Makerspace site.

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