Author Archives: Rohan Kapoor

Quick Maintenance Update

I recently became aware of several problems with the website’s contact form system leading it to purge all incoming messages (or leave them hanging without pulling them in). I’ve made several changes today which should resolve that series of problems. If you’ve tried to send me an email recently and noticed that it didn’t go through, I apologize. It should be working at this point.

Independence Day Fireworks 2012

I took these shots in Worcester MA, on July 3rd (Worcester always does the fireworks a day early to not coincide with the Boston ones) off of an I-290 freeway ramp. I was actually running a little late (packing up my camera gear as this was my first time shooting fireworks) and so we didn’t make it all the way to where we normally watch from. We had a really good view though literally at the bottom the exit ramp. We went down the ramp and like everybody else there, pulled over the side. I didn’t even have time to get the tripod out, the fireworks started so suddenly – so I just put a camera (a Canon T3) on top of the parked minivan, connected up my remote trigger, turned on bulb mode and hoped to get lucky.

Out of more than one hundred shots or so, these nine shots were my favorite. A lot of them have a somewhat wavy, squiggly feel to them – something I thought was really cool artistically!

These were shot on a Canon T3 with a Canon EF 70-300mm f/4-5.6 IS USM Lens at ISO 100 in bulb mode with a remote trigger.

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Configuring the Raspberry Pi as an AirPrint Server

As a $35 pc with very low power requirements, the Raspberry Pi is uniquely suited to serve many different purposes especially as an always-on low power server. When I first heard of the Pi, I was excited because I wanted it to become an AirPrint Server. This allows Apple’s iOS line of devices to print to the Raspberry Pi which then turns around and prints to your regular printer via CUPS. I used my network laser printer for this, but there is no reason why you couldn’t use a hardwired printer (over USB) on the Pi itself. About a month ago, I succeeded. Last week, I put up a video demonstrating it, and today, I bring you the long-promised tutorial so that you can set it up yourself.

I’d like to thank Ryan Finnie for his research into setting up AirPrint on Linux and  TJFontaine for his AirPrint Generation Python Script.

For the purpose of this tutorial, I used PuTTY to remotely SSH into my Raspberry Pi from my Windows 7 running Desktop PC.

To begin, let’s login to the pi which uses the username pi and password raspberry.

We now have to install a whole bunch of packages including CUPS and Avahi. Before we do this, we should update the package repositories as well as update all packages on the Raspberry Pi. To update the repositories, we type in the command sudo apt-get update.

Naturally, this doesn’t quite work as expected, ending with an error requesting another package update. If you get this error just type in sudo apt-get update again.

It seems the second time is the charm!

Now we need to upgrade the packages installed on the Pi using the new repository information we’ve just downloaded. To do this, we type in sudo apt-get upgrade.

This will generate a list of packages to install and will then request approval before continuing. Just type in y and press enter to let it continue.

This will take a few minutes as it downloads and installs many packages. Eventually you will be returned back to a bash prompt.

At this point, we have to begin to install all of the programs that the AirPrint functionality will rely on: namely CUPS to process print jobs and the Avahi Daemon to handle the AirPrint announcement. Run sudo apt-get install avahi-daemon avahi-discover libnss-mdns cups cups-pdf gutenprint pycups avahi python2 to begin this install.

Looks like some of those have been deprecated or had their names changed. We’ll have to install those ones again in a minute.

For some strange reason CUPS didn’t get installed, even though it was the list of programs to install in the last command. Run sudo apt-get install cups to fix this.

Once again, it will need confirmation before continuing. As before, just type in y and press enter to continue.

Once it finishes, you will again be returned to the bash prompt.

Time to install python-cups which allows python programs to print to the CUPS server. Run sudo apt-get install python-cups to install.

Once you’ve returned to the bash prompt, run sudo apt-get install avahi-daemon to install the avahi daemon (an mDNS server needed for AirPrint support).

For security purposes, the CUPS server requires configuration changes (managing printers, etc) to come from an authorized user. By default, it only considers users authorized if they are members of the lpadmin group. To continue with the tutorial, we will have to add our user (in this case pi) to the lpadmin group. We do this with the following command: sudo usermod -aG lpadmin pi (replace pi with your username).

Before continuing, lets start the cups service and make sure the default configuration is working: sudo /etc/init.d/cups start.

Since we just tested CUPS’s default configuration, we might as well do the same to the Avahi-Daemon: sudo /etc/init.d/avahi-daemon start.

If you get any errors during the previous two startup phases, it is likely that you didn’t install something properly. In that case, I recommend that you go through the steps from the beginning again and make sure that everything is okay! If you proceed through without any errors then it’s time to edit the CUPS config file to allow us to remotely administer it (and print to it without a user account on the local network – needed for AirPrint). Enter in sudo nano /etc/cups/cupsd.conf.

The configuration file will load in the nano editor. It will look like this.

Use the down arrow until you come to the line that says Listen localhost:631.

This tells CUPS to only listen to connections from the local machine. As we need to use it as a network print server, we need to comment that line out with a hashtag(#). As we want to listen to all connections on Port 631, we need to add the line Port 631 immediately after the line we commented out.

We also need to tell CUPS to alias itself to any hostname as AirPrint communicates with CUPS with a different hostname than the machine-defined one. To do this we need to add the directive ServerAlias * before the first <Location /> block.

To continue setting up remote administration, there are several places that we need to enter the line Allow @Local after the line Order allow, deny – however this does not apply to all instances of that line.

We now need to save the CUPS config file and exit the nano text editor. To do this hold down ctrl and press x. You will be prompted to save the changes. Make sure to type y when it prompts you.

It will then ask you to confirm the file name to save to. Just press enter when it prompts you.

Next, we need to restart CUPS to have the currently running version use the new settings. Run sudo /etc/init.d/cups restart to restart the server.

It’s time to find out the Pi’s IP address to continue setting up printing via the web configuration tool. In my case, my Pi is assigned a static address by my DHCP server of 192.168.1.75. To find out your Pi’s IP address, just run ifconfig.

Once we have the IP address, we can open a browser to the CUPS configuration page located at ip_address:631. More than likely you will see a security error as the Raspberry Pi is using a self-made SSL certificate (unless you have bought and installed one).

To continue on, click on Proceed anyway or your browser’s equivalent if you are sure you have entered in the correct IP address. You will then see this screen.

From there, go ahead and click the Administration tab at the top of the page. You will need to check the box that says Share Printers connected to this system and then click the Change Settings button.

CUPS will request password authentication, and since we added the user pi to the lpadmin group earlier, we can login with the username pi and password raspberry.

The CUPS server will write those changes to it’s configuration file and then reboot.

At this point, it is time to setup your printer with CUPS. In my case, I am using a Brother HL-2170w network laser printer and my screenshots will be tailored to that printer. Most other printers that are CUPS compatible (check http://www.openprinting.org/printers for compatibility) will operate the same way. If you are using a USB printer, now is the time to plug it in. Give it about a few seconds to get recognized by the Pi and then click the Add Printer button to begin!

CUPS will begin looking for printers. Just wait till it comes to a list of discovered printers.

Eventually you will come to a page that looks like this:

Once you have chosen the correct printer and clicked continue – you will be brought to the settings page. Make sure to check the box regarding sharing or AirPrint may not work correctly.

You will then have to select the driver for your printer. In most cases, CUPS will have the driver already and all you need to do is select it – but with newer printers, you will need to get a ppd file from the OpenPrinting database and use that.

Then you need to set the default settings for the printer, including paper size and type. Make sure those match your printer so that everything prints out properly.

Once you are done, you should see the Printer Status page. In the Maintenance box, select Print Test Page and make sure that it prints out and looks okay.

If you get a proper test page, then you’ve successfully setup your CUPS server to print to your printer(s). All that’s left is setting up the AirPrint announcement via the Avahi Daemon. Thankfully, we no longer have to do this manually, as TJFontaine has created a python script that automatically talks to CUPS and sets it up for us! It’s time to go back to the Raspberry Pi terminal and create a new directory. Run sudo mkdir /opt/airprint to create the directory airprint under /opt/.

We next need to move to that directory with the command cd /opt/airprint.

Now we need to download the script with the following command: sudo wget -O airprint-generate.py --no-check-certificate https://raw.github.com/tjfontaine/airprint-generate/master/airprint-generate.py

Next, we need to change the script’s permissions so that we can execute it with the command sudo chmod 755 airprint-generate.py.

It’s time to finally run the script and generate the Avahi service file(s). Use the command: sudo ./airprint-generate.py -d /etc/avahi/services to directly place the generated files where Avahi wants them.

At this point everything should be working, but just to make sure, I like to do a full system reboot with the command sudo reboot. Once the system comes back up, your new AirPrint Server should be ready!

To print from iOS, simply go to any application that supports printing (like Mail or Safari) and click the print button.

Once you select your printer, and it queries it and will send the printjob! It may take a couple minutes to come out at the printer but hey, your iOS device is printing to your regular old printer through a Raspberry Pi! That’s pretty cool and functional right? And the absolute best part, since the Raspberry Pi uses such little power (I’ve heard it’s less than 10 watts), it is very cheap to keep running 24/7 to provide printing services!

UPDATE: If you are running iOS6, due to slight changes in the AirPrint definition, you will have to follow the instructions here, to make it work. Thanks to Marco for sharing them!

Clothing the Raspberry Pi (Or Getting the Raspberry Pi a Case)

Before I even had a Raspberry Pi, I purchased this project box from eBay hoping that from the schematic measurements of the Raspberry Pi, it would fit. When I got my Raspberry Pi on April 19th, I was much more concerned with playing with it and my upcoming AP exams than casing it. This past weekend, I pulled out the project box and began to fit the Raspberry Pi inside it.

I used an X-Acto knife to cut out the pieces of plastic from the box. The USB ports, RCA jack, and headphone jack all stick out past the sides of the box – to make them fit, I had to trim down extra material from the top of the box to allow them to slip in. The rest of the ports are flush except for the power jack and sd card slot, both of which are less than 1 inch shy of the box’s edge. For those ports that didn’t need to be cut top-down, I used the Punnet template to get the sizes of the ports down correctly. I taped it onto the project box sides and then used a drill to take out most of the holes. I then used the X-Acto knife to straighten them out.

To provide a bed for the Pi to sit on, I cut out strips from the pink piece of foam that the Pi shipped on and hotglued a small piece in each corner the Pi would touch.

Overall, I am very pleased with how my case for the Raspberry Pi came out, even though it’s not perfect by any means. I just wish their store was available again so that I could buy a couple of Raspberry Pi logo stickers for the plain box.

So far, I’ve tested it with the box closed for 3 days running as an AirPrint server (see the demo) and have not had any overheating issues. To the touch, the lid of the box is a little warm but nothing significant. I’ve included a small photo gallery for anyone interested.

Project Box (Closed)

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Demonstration: Raspberry Pi Running as an AirPrint Server

A few weeks ago, I wrote about setting up the Raspberry Pi to function as an AirPrint Server. This has the effect of allowing Apple’s ios devices to print to regular unix printers (that are accessible to CUPS) using the avahi-daemon for announcements. I’ve gotten all of this to work reliably on the Raspberry Pi and have been testing it out for the last several weeks. I know I promised a tutorial, but it has been rather slow going. The tutorial is coming soon – but today, I have a small video demonstration which shows how well this works.

The one thing I have noticed is that printing via AirPrint is a little slower than printing natively to the printer. My reasoning for that is twofold: One the limited processing power on the Raspberry Pi may be affecting the PDF rasterization time. And two, my Raspberry Pi is connected to a wireless ethernet bridge (802.11g) while the iPad is connected to the wireless access point (802.11n) so there is likely some lag caused by wireless network signals. All things considered, I am currently able to print from the iPad to my network printer (which itself is not AirPrint compatible) having spent on $35. This is the power of the Raspberry Pi!

Stay tuned for the tutorial – it’s on it’s way.

 

Raspberry Pi Working as AirPrint Server

As I just posted on Twitter, I have successfully gotten my Raspberry Pi to function as an AirPrint Server for ios devices. This allows any of the ios devices connected to my WiFi network to print to my network printers which do not support native AirPrint functionality. It was a bit convoluted to set up and did require a heavy usage of the terminal but in the end it was totally worth it! It took me about 35 minutes to setup (including the 2 minutes I spent wondering why the iPhone couldn’t find the printer before I realized the WiFi was off)!

A tutorial (with step by step instructions) and a video demonstration will be coming out on Saturday, so stay tuned!

“Americanizing” the Raspberry Pi

The Raspberry Pi is made by the Raspberry Pi Foundation, a UK charity organization. For this reason the Debian SD card image (and presumably the others) default to the English – UK locale, timezone, and keyboard layout. For those of us in America, this is clearly not going to work! Clayton Smith excellently documents the procedure for Canadian’s in this post on his blog. I followed his procedure, replacing en_CA with en_US. To make it a little easier to follow, I have turned this into a photo-tutorial using PuTTY to remotely SSH into the device from my Windows 7 running Desktop PC.

First up is logging in, which uses the username pi and password raspberry.

Next, change the system locale from en_GB.UTF-8; to en_US.UTF-8 by running the command sudo dpkg-reconfigure locales.

Use the arrow keys to move up/down and highlight options. Use the spacebar to select/deselect the options.

Press tab to select <Ok> and then press enter.

Confirm your selection.

The Raspberry Pi will now generate the selected locales.

Now, it’s time to set the keyboard layout. Run the command sudo dpkg-reconfigure keyboard-configuration.

Next, we need to set the timezone. Run the command sudo dpkg-reconfigure tzdata.

Use the up/down arrows to select the appropriate location and press enter.

Use the up/down arrows (again) to select the appropriate timezone (closest city in your timezone) and press enter.

The Raspberry Pi will acknowledge the timezone change.

Next up is to modify the Debian packages source to use the US mirror (rather than the British one). Run the command sudo vi /etc/apt/sources.list.

Change the uk to match your two digit country code (us for me).

Write the changes to disk by pressing escape and then entering :w and pressing enter.

vi (the text editor) will confirm that the changes were written to the disk.

Quit vi (the text editor) by entering :q and pressing enter.

Then, run sudo apt-get update to update the package lists with the new source.

Finally, run sudo reboot to reboot the Raspberry Pi and confirm your changes.

Congratulations, your Raspberry Pi has been “Americanized!”