Monthly Archives: September 2012

Raspberry Pi a la Node – Running nodejs on the Raspberry Pi

My local hackerspace Sector67 held a 24 hour build fest this weekend. Late last week in preparation for the event a few of us purchased some Raspberry Pi‘s.  If you’re not familiar with the Pi, it’s a credit card sized ARM based computer with a USB port, Ethernet port, GPU,  HDMI and Composite video out that runs Linux for about $35.  You can read more about it at the link above but the “overall real world performance is something like a 300MHZ Pentium 2, only with much, much swankier graphics.”

I bought 2 with the plan to install nodejs on them.  I figured it’d be a super cheap way to create a web based controller people could use in other projects.  I’m happy to say it only took me about 3 days to make this a reality.  However it was pretty much 3 days of frustration that I’d like to keep the rest of you from having to experience so here’s the scoop.

I bought the bare bones Raspberry Pi for $35.  When you buy the bare bones card you’re going to need some more hardware to make it run. Here’s a quick list:

1) Class 4 SD card from 4 gigs to 32 gigs in size.  The Pi uses this for its boot device.
2) A 5v 700mA micro usb power supply.
3) A powered usb hub.
4) USB Mouse/keyboard.
5) A monitor with HDMI input or an HDMI to DVI converter if your monitor is DVI only.
6) An SD card reader/writer to image the SD card with the linux boot image.

My Pi’s arrived in the middle of the week along with the 2 32g SD cards I ordered off Amazon.  I rooted around my junk hardware closet and dug out an extra USB keyboard/mouse and an old Blackberry phone power supply that was 5V/650mA micro USB.  The one thing I realized I was missing was an SD card reader/writer.  I made a quick search on the internet and found that my local Target claimed to have a $10 cheap-o reader in stock.  Of course when I got there they didn’t have it but they did have a $20 Belkin universal media writer as well as a couple of powered USB hubs on closeout for $5 each.  So I grabbed them and headed over to Sector67 to get things up and running.

The first order of business was to get the linux images on to my SD cards.  I decided to do this from my Windows based laptop so I downloaded the latest Debian image from the Raspberry Pi download page.  The actual release I picked up was the September 18th Raspbian “Wheezy” image.  After downloading and unzipping the image I was left with an .img file I needed to get onto the SD cards.  In order to facilitate this I needed a piece of imaging software called Image Writer for Windows.  After downloading and installing this I was able to quickly image both my SD cards with the Raspbian .img file.

Here’s where I ran into my first problem.  I have a Dell monitor with HDMI input but I didn’t have it at Sector.  I had an HDMI cable with an HDMI to DVI converter but when I plugged it in all I got was a blank screen.  I tried it with both Pi’s and both of them did the same thing.  Ok fine, the Pi’s also have a composite video output so I tried that next.  Same problem.  For some reason when I plugged both the composite and HDMI/DVI in at the same time I suddenly got video out through the HDMI/DVI combo.  If I unplugged the composite or the HDMI/DVI neither output would work.  If I plugged them both back in then the HDMI/DVI would work.  At least it allowed me to get working on the thing.  Later on I switched to my HDMI monitor with a straight HDMI connection and everything was fine.  However, I did experience some weirdness in that occasionally I would get a weird “puttering” sound through the HDMI audio.  This happened on both Pi’s so I’m not quite sure what’s up with that.

I was finally up and running with a basic Linux image on my Pi.  Now it was time to try and get nodejs up and running.  I did some looking around the web and the best article I could find was this one from July.  It looked highly promising.  Here’s where I ran into my next gotcha.  While editing with VI I found that I couldn’t enter a # character on my keyboard.  I got around it by cutting and pasting a # from somewhere else in the document but a few minutes later when I needed to use the | character on the command line I knew I was going to have to fix the problem.

The image that is on the Raspberry Pi website was obviously generated by someone in the UK as the keyboard settings are set for a UK keyboard and this is what was causing me grief.  To fix this issue you first have to type in the following:

$ sudo dpkg-reconfigure keyboard-configuration
You’ll have to go through a few dialog boxes to select your keyboard and the region of US.  At one point you have to select Other to get to the other regions besides the UK ones.After finishing you can reboot the system or just do the following:

$ sudo invoke-rc.d keyboard-setup start
Moving on with a functional keyboard I followed the instructions in the article and downloaded the 6.15 node distribution and attempted to get it compiled on the Pi.  So here’s where things started to suck.  The first thing I found was it took anywhere from a 90 minutes to 2 hours to compile the v8 library on the Raspberry Pi.  I immediately, and by immediately I mean 90 minutes later, I ran into a problem when trying to link the library.  After searching around the net for a solution I found what I thought was my issue and recompiled.  90 minutes later I ran into another issue.  This went on for some time with trying different compiler options to get things working.  After 4 hours or so of frustration I decided to head home and work on it there.  Here came my next problem.  In my haste to head home I didn’t bother issuing a

$ sudo halt
so when I got home my SD disc image was corrupted and wouldn’t boot correctly.  Awesome.  So after a re-imaging of the card, upping the file system to use all the card, (I didn’t mention this earlier but you need to do this to use all the space on the card and it takes like 30 minutes), and fixing the keyboard thing I was ready to go back at it.Now for another woe.  The Pi has an option to overclock/overvolt it for better performance.  In the past this wasn’t recommended and could void your warranty.  As of the latest release there is a turbo mode that lets you crank up your 700MHz processor in a variety of steps to 1GHz.  However they note that you need to “test stability” as it’s dependent on your Pi and your power supply.

At this point I was getting pretty frustrated with compile times so I cranked that baby up to 1GHz, re-downloaded node and got to work compiling.  Unfortunately this ended really quick as for some reason the node compile died almost immediately.  I took a look at the file that wouldn’t compile and found that the text file was corrupted.  Turns out that my “stability” was not good.  I assumed that my power supply was not up to the job, so I cranked my CPU back down to 700 MHz and reformatted again to get rid of my corrupt files.

I continued to get nowhere with building node and spent a lot of time searching for other ways to get it to build.  I probably tried 3 different articles that people had posted as well as one binary distribution that immediately died with a segmentation fault.  Finally on Saturday morning I came across this gist.  This is the one that made it all happen.  Down near the bottom is the post from a month ago with the script that worked for them as well as me:

export NODE_VER=0.8.7
cd ~
rm -rf ~/work/node-build/node-$NODE_VER;mkdir -p ~/work/node-build && cd ~/work/node-build
rm -rf ~/opt/node-$NODE_VER;mkdir -p ~/opt/node-$NODE_VER

curl -O

curl$NODE_VER/node-v$NODE_VER.tar.gz | tar xz
cd node-v$NODE_VER
git apply --stat --apply ../arm-patches-2.patch

./configure --shared-openssl --without-snapshot --prefix=~/opt/node-$NODE_VER

date;time make CFLAGS+=-O2 CXXFLAGS+=-O2 install;date

If you copy this into a shell script and run it you should get an actual build of node 0.8.7 and npm that works.  After the build I was quickly able to install express and have a web site up and running on the Raspberry Pi.  I was also able to install the serialport library for nodejs and talk to an Arduino board over the USB connection (a topic for another day).

I was so excited to have node running that I even went ahead and compiled redis for the Pi as well.
I just pulled down the distribution off this link  and did a

$ make -j 2
When it’s done it will tell you to run “make test” which I did as well just for grins.  This takes quite a while to run but it passed everything for me.I’m really looking forward to messing around with this more.  A super cheap, super tiny embedded linux system that is powered by nodejs has got me fired up to put all sorts of stuff online.  A HUGE HUGE tip of the hat to Adam Malcontenti-Wilson for the gist that got me up and running.

Finally here’s the obligatory screenshot of my Raspberry Pi running the default Express installation on nodejs.



Yoga, Morse Code, and that Damn Song!

After an extended break I’m back to doing yoga 3 or 4 times a week.  I roll out for the 6 am class at Capital Fitness, grab a coffee on my way back from Pinkus Mcbride and by 7:15 I’m drinking it while catching up on the webs.

I really enjoy yoga.  It gives me an hour to center myself and pretty much changes my attitude for the day.  I can tell when I’ve been away from it.  It’s hard to get other tech guys to try it out but luckily I know a few who have and they’ve become converts as well.

Last Monday I got up, got all my stuff together and headed out the door at 5:50 A.M.  It takes me 5 minutes to walk to the studio so my timing was perfect. I got down to the elevators and after pushing the button I heard it.  There was a faint electronic sound coming from somewhere that was going “Beep beep beep, beeeeeep beeeeeep beeeeep, beep beep beep”.  3 short beeps, 3 long beeps, and then 3 short beeps.  Now maybe it’s because I’m old or was a boy scout, but I recognized that immediately as SOS, the international Morse code cry for help.

I tried to track the source but couldn’t get a bead on where it was coming from.  At the same time another tenant came out in scrubs obviously headed off to his job at a hospital somewhere.  I asked him if he heard the beeping and he said “Yeah it’s been doing that for a while.”  I said “Well that’s Morse code for SOS” and he responded, “Whoa you’re right, you should call our landlord or 911 or something.”  He then jumped in the elevator and took off.

Now there is no way I’m making it to yoga.  There are people out there who will roll into yoga class late.  I’m not one of them.  It’s just too disruptive and not good manners. I’m thinking calling 911 is not a great idea. The only solution is to call my landlord.

Our landlord is a pretty cool guy and he lives right above us in our building.  This is great since when something is wrong in the building it’s typically fixed immediately.  I happen to have his cell phone so I decided it was time to wake him up.  I went back to our apartment and gave him a ring.  After a sleepy “Hello” I explained what was up and I’m pretty sure he was thinking “WTF, why are you calling me about this” but he agreed to meet me at the elevators in a couple minutes.

After hearing the beeping from the air vent he agreed that something was up.  We headed down a floor and couldn’t hear anything, so we went back up a couple floors where the sound was loudly emitting from a service closet.  After unlocking it the cause was pretty apparent.  The drain for the building’s air conditioner was clogged and water was pooling in the closet.  My landlord had put a moisture meter in the room for this very occurrence and it was sending out the “SOS” message over and over.

I was a little pissed at this point.  Wouldn’t an annoying electronic “whoop whoop”, or siren, or anything other than “SOS” have been just as effective?  Perhaps not as it probably wouldn’t have stopped me in my tracks on the way to yoga if it had been anything else. But still……

Later in the day I sent him an email apologizing for getting him out of bed at 6 A.M. but that it would make a good blog post. His response was

"I was almost up anyway and better safe than sorry.  
You're right--you are likely the only person who knows the SOS sequence. 

Please be sure to list how quickly McBride responded too."

So if you’re ever looking for an apartment know that McBride Companies has awesome response time to apartment issues, even if they have annoying Flash Music on their website. Seriously go listen to it.

Thursday morning I went off for my usual 6 am Yoga class.  Before the class got rolling our instructor Erin said we’d be working on opening up for Hanumanasana, also known as the splits, not exactly my forte. She also said she had put together an inspirational playlist for the day.

Now  if you asked me to name what tranquil yoga song we’d be starting off with I can guarantee you that my first 10,000 guesses would not be the song that haunts my life, Europe’s Final Countdown.  If you remember, it was only a few months ago I last ran into this song outside my bedroom window.  When it came on I pretty much lost it. I was laughing so hard I couldn’t even pay attention to what was going on.

As a bonus here’s a couple of pretty decent yoga type tunes relating to the Monkey God,  Hanuman. One is by MC Yogi and the other one by Wah.