public class ObjectPair<A, B> {
    private A primary;
    private B secondary;
 
    public ObjectPair(A primary, B secondary) {
        this.primary = primary;
        this.secondary = secondary;
    }
 
    public A getPrimary() {
        return primary;
    }
 
    public B getSecondary() {
        return secondary;
    }
 
    @Override
    public String toString() {
        return "(" + primary.toString() + ", " + secondary.toString() + ")";
    }
}

Sometimes you’ll see more specific classes like ObjectWithString, but the idea is the same. This approach is fine for many common tasks, but if you find yourself needing multiple cardinalities of tuple, this approach get’s tedious quickly, as you find yourself writing ObjectTriple, ObjectFourTuple, ObjectFiveTuple, and so on. Thinking that it would be smart to have one class that could create a tuple of any length, you might end up being tempted to write a class like this:

public class Tuple<A> {
    public static Tuple<A> getTuple(A... args) {
        return Tuple(args);
    }
 
    private A[] items;
 
    private Tuple(A[] items) {
        this.items = items;
    }
 
    public A getItem(int index) {
        return items[index];
    }
}

But this is even worse than what we had before! Not only are we limited to one type of object (which adds the major headache of unsafe casting to a common use of tuples) but we no longer have any idea of how many items our tuple holds. This approach seems to be a real step backwards, as it’s really just a wrapper around an array, which gets rid of any advantage of having a tuple type available.

To make the single-class approach work, we’ll need some way of storing more information in the type of our tuple objects, by taking an idea from functional programming. We define a type that contains information about how long our tuple is, and what type exists at each location. This recursive type is simply defined, but allows us to create tuples of any length:

public abstract class Tuple<T, U extends Tuple> {
    public abstract T getItem();
    public abstract U getTuple();
 
    public static final <T> Tuple<T, EmptyTuple> getTuple(T item) {
        return new SingleItem<T>(item);
    }
 
    public static final <T, U extends Tuple> Tuple<T, U> getTuple(T item, U tuple) {
        return new SingleItemAndTuple<T, U>(item, tuple);
    }
 
    public static abstract class EmptyTuple extends Tuple {}
 
    private static class SingleItem<T> extends Tuple<T, EmptyTuple> {
        private T item;
 
        public SingleItem(T item) {
            this.item = item;
        }
 
        public T getItem() {
            return item;
        }
 
        public EmptyTuple getTuple() {
            return null;
        }
    }
 
    private static class SingleItemAndTuple<T, U extends Tuple> extends Tuple<T, U> {
        public T item;
        public U tuple;
 
        public SingleItemAndTuple(T item, U tuple) {
            this.item = item;
            this.tuple = tuple;
        }
 
        public T getItem() {
            return item;
        }
 
        public U getTuple() {
            return tuple;
        }
    }
}

Now we have all of the tuple type-safety we could want, at the expense of clumsy notation:

class TupleTest {
    public static void main(String[] args) {
        Tuple<String, Tuple<Integer, Tuple.EmptyTuple>> tuple = Tuple.getTuple("Test", Tuple.getTuple(Integer.valueOf(1)));
        System.out.println(tuple.getItem());
        System.out.println(tuple.getTuple().getItem());
    }
}

To do this, open /etc/default/grub in a text editor and find the line that reads

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

and change it to read

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=normal"

Rebooting your computer should leave the grub menu and boot splashscreen unchanged, while the virtual terminals work perfectly! Of course, your mileage may vary, depending on your system. This works for me on a fully updated install of Ubuntu 12.04, with an NVIDIA 9800 GT.

You can check it out on the Google Maps site here.

I’ve also uploaded a script I wrote called get_quad.py, which will download USGS topographic maps automatically. This script naturally complements gdal_slice.py; using the two together allows for almost-totally automatic population of GPSdrive’s map database with high quality topographic maps.

usage: get_quad.py [-h] [-q] [-s STATE] (-g | -c COORD COORD)

Get DRG USGS quad for given latitude and longitude from LibreMaps.org

optional arguments:
 -h, --help show this help message and exit
 -q, --silent don't produce any output
 -s STATE, --state STATE
 Postal abbr. for the state in which the quad falls, so
 we don't need to look it up
 -g, --gps get coordinates from GPSd
 -c COORD COORD, --coords COORD COORD
 specify latitude N and longitude E (respectively) in
 decimal degrees; longitude should be negative, as all
 maps fall in the western hemisphere

Unfortunately, because of the way USGS maps are organized, the script needs to know the state in which the coordinates fall. If the -s flag is not given, this is inferred from the coordinates, but this lookup requires internet access.

The first step was downloading an app to the phone. I used the free GPS over BT, but the steps should work with most other programs like it.

Once that’s up and running, it’s time to pair your computer and phone. Make sure that the GPS to BT program is running at this point!

If everything worked properly, you should see the following:Make sure that it says “A computer serial port was created”. If it doesn’t say this, your computer didn’t pick up on the serial data stream from the GPS program, and you should retry pairing.

Once OS X has created a serial port, you simply need to point GPSd at it. In a terminal, run

ls /dev/tty.*

One of the results should be /dev/tty.[[devicename]]-BluetoothService — this is what to point GPSd at:

sudo gpsd -n /dev/tty.[[devicename]]-BluetoothService

and you should be up and running!

At the moment there is one caveat: you have to re-pair your devices each time you want to fire up the GPS — at the moment OS X seems unable to open the bluetooth serial port on request. Other than that, it works like a charm!

Although I had never been aware of the term “indie web” (which seems to have been around for almost 15 years, judging by this article from uzine.net), I’ve been building my own independent web presence for more than four years. In the words of the IndieWebCamp home page:

Rather than posting content on many third-party silos of content, we should all begin owning the content we’re creating. Publish short status updates on your own domain, and syndicate to Twitter. Publish photos on your own domain, syndicate to Flickr, etc, etc.

For some good summaries of the ideas and goals of the IndieWebCamp, this article from GigaOm and this post from Mark Hendrickson are a great place to start, while each of the camp’s guests also have their own websites, each with a wealth of information.

While I’ve been using this domain for quite a while, it’s been in use alongside Facebook, Delicious (and Flickr, to a smaller degree) as a part of my web presence. However, since I ditched Facebook five or six months ago, I’ve been relying on this domain for more, and overall I’ve been pleased. However, as the IndieWebCamp is readily willing to admit, there is room for a lot of room for technical innovation in expanding the functionality of the indie web. Towards that end, I see three threads of work that I’m interested in pursuing:

• Using my site for Flickr-like photo sharing. While this might include syndication to Flickr at some point, I mostly want a light-weight DIY solution to photo sharing.
• Similarly, using my site for bookmarking. I really like the service that delicious offers, but I want to own the data and let delicious simply keep a copy of it (see http://adactio.com/journal/4197/ for some ideas).
• Finally, I’m hugely enamored of the work on delivery-agnostic messaging that took place at IndieWebCamp, which you can find details of here. Not only is it a ridiculously simple protocol, but it starts to address some real issues of a distributed social web, in that it allows two-party communication based solely on domain names as unique identifiers, therefore eliminating the middleman in social-web-type communications.

Luckily, I quickly found out that GDAL ships with Python bindings. I installed GDAL from source using the instructions from their wiki. To make sure it built with Python modules I ran ./configure –with-python. After that make and sudo make install ran without a hitch.

I then set about re-implementing gdal_slice.sh in Python. Once I got a handle on how to use the Python bindings it was fairly easy to write. You can find the script here.

Using gdal_slice.py is very similar to using gdal_slice.sh:

$ ./gdal_slice.py -h
Usage: gdal_slice.py [options] FILENAME

Options:
  -h, --help            show this help message and exit
  -o OVERLAP, --overlap=OVERLAP
                        percentage tiles will overlap. should be at least 20%
  -a, --add             write map info to map_koord.txt in current working
                        directory
  -m, --map             use *_map folders for output; use if input image is
                        UTM. Default behavior
  -t, --topo            use *_top folders for output; use if input image is
                        not UTM
  -v, --verbose         enable debugging output

The biggest difference is that gdal_slice.py does not perform any format conversion; it will write maps to TIFF files. Although the file size is decidedly larger than that of PNGs, my version of GDAL is unable to create PNGs, and disk space is (fairly) cheap. If I’m motivated I’ll get around to adding a format option, at least to allow conversion to PNG.

Running gdal_slice.py filename.ext will create a folder named filename_map (or _top, if you use the -t flag) that contains a set of 1280×1024 TIFF files, as well as a map_koord_draft.txt file. Moving this folder into GPSDrive’s map directory, and merging filename_[map|top]/map_koord_draft.txt with map_koord.txt will make the new maps available to GPSDrive. Note that filename.ext must be in the current working directory, as the script handles filenames/paths somewhat naivëly.

So far I’ve only tested this with GeoTIFFs from LibreMaps, but it seems to work great, with the caveat that LibreMaps’ files include the borders of map, and my script doesn’t do any cropping, so you see borders if you’re near the edges of quads. This doesn’t bother me terribly much, but you may need to turn mapsets on and off in the Map Control dialog to see the appropriate images.

Update 7-14-11: I’ve modified the script with an additional flag (-a) that will automatically merge the generated map_koords file with map_koord.txt in the current working directory. This means that if you run the script from inside .gpsdrive/maps with the -a flag the generated tiles will be automatically added to GPSDrive’s database. The script avoids creating duplicate entries in map_koord.txt, as well as alphabetizing all entries.

I’ve modified the documentation here, as well as the links, to reference the latest version.

To get GPSDrive running I had to do a little bit of fiddling, but it’s fairly easy. First off, I needed to downgrade GPSd from 2.96 to 2.95 — apparently the newest version introduced slight changes to the library that GPSDrive hasn’t yet picked up. However, building the two versions is exactly the same — see my post on building 2.96 for instructions that apply to 2.95. You can get the source package for either version here.

Next I used homebrew to install the dependencies that GPSDrive needs by running brew install gtk+ cairo gtkglext postgresql gettext. Note that these are just the packages I didn’t have going into the build — you may need more, depending on your setup.

With preliminaries out of the way, I downloaded gpsdrive-2.11 from here. As per their build instructions I created a build directory (mkdir build), moved into it (cd build), and then ran cmake. After some serious wrestling with dependency locations and linker flags I figured out the following two steps to get GPSDrive to compile and build.

First, because GPSDrive seems to want to automatically link against libcrypt, which OS X bundles in it’s libc, you need to tell cmake not to use it. I couldn’t figure out how to do with with a cmake configuration option, so I edited gpsrive-2.11/src/CMakeLists.txt and commented out (put a # in front) of the two lines containing the word “crypt”. You could also delete these lines — it has the same effect. This is along the lines of the patch here (see the attachment), that was posted to the GPSDrive mailing list last year, when I pointed out this bug. Sadly, the patch has not been applied to the source tree yet, but I can attest it works, if you care to apply it yourself.

With that out of the way, we can now run the following command from inside the build directory.

cmake -DCMAKE_BUILD_TYPE=Debug\
 -DWITH_FRIENDSD=OFF\
 -DWITH_KISMET=OFF\
 -DWITH_MAPNIK=OFF\
 -DWITH_POSTGIS=OFF\
 -DWITH_SPEECH=OFF\
 -DLIBGPS_OLD=OFF\
 -DGTK2_ATK_INCLUDE_PATH=/usr/local/Cellar/atk/2.0.0/include/atk-1.0\
 -DGTK2_GLIBCONFIG_INCLUDE_PATH=/usr/local/lib/glib-2.0/include\
 -DGTK2_GLIB_INCLUDE_PATH=/usr/local/include/glib-2.0\
 -DGTK2_PANGO_INCLUDE_PATH=/usr/local/Cellar/pango/1.28.4/include/pango-1.0\
 -DGTK2_CAIRO_INCLUDE_PATH=/usr/local/Cellar/cairo/1.10.2/include/cairo\
 -DGTK2_GDKCONFIG_INCLUDE_PATH=/usr/local/Cellar/gtk+/2.24.4/lib/gtk-2.0/include\
 -DGTK2_GTK_LIBRARY=/usr/local/lib/libgtk-x11-2.0.0.dylib\
 -DCMAKE_C_FLAGS="-I/usr/local/Cellar/gdk-pixbuf/2.22.1/include/gdk-pixbuf-2.0"\
 -DCMAKE_EXE_LINKER_FLAGS="-lgdk_pixbuf-2.0.0 -lpango-1.0.0 -lgobject-2.0.0 -L/usr/local/Cellar/gettext/0.18.1.1/lib -lintl"\
 -DMSGFMT_EXECUTABLE=/usr/local/Cellar/gettext/0.18.1.1/bin/msgfmt\
 ..

After cmake generates all the necessary files, you can run make, and assuming it doesn’t give you errors, ./src/gpsdrive will allow you to test your newly built executable, and sudo make install will install it.

Once GPSDrive is up and running you should be able to see your current location (assuming you have a GPS connected to GPSd). If you want to get maps, you can download them from within GPSDrive, which has support for OpenStreeMap tiles, as well as NASA Landsat images (although I haven’t been able to get Landsat to download correctly).

Cryptonomicon

Randall Lawrence Waterhouse

Current meatspace coordinates, hot from the GPS receiver card in my laptop:

8 degrees, 52.33 minutes N latitude 117 degrees, 42.75 minutes E longitude

Nearest geographical feature: Palawan, the Philippines

(from http://www.euskalnet.net/larraorma/crypto/slide51.html)

Using GPSd’s python bindings, and the free, CC-licenced RESTful API from GeoNames.org, I wrote a short python script that will produce a similar output:

Seth Just

Current meatspace coordinates, hot from the GPS receiver card in my laptop:

41.751 N latitude, 111.807 W longitude

Nearest geographical feature: Logan Canyon, Utah, United States

The core of the script is two functions — one that gets GPS coordinates from GPSd, and a second that does a lookup for geographical features (mountains, canyons, islands, etc) on GeoNames.org. For more details, see the final section of this post.

Using gpssig.py

To use gpssig.py, first download it from here, and change the extension to .py.

In order to be useful as an email signature, I had to produce output in HTML format, which allows almost any mail client to use the output as a signature. I’ve gone through the effort of setting it up with the two clients I use the most: Mozilla Thunderbird and Apple’s Mail.app. Of these two, Thunderbird has documented support for HTML signatures (see here for details), and should be the most like other email clients. This script has been tested on Mac OS X Snow Leopard, and should run on Linux without problems (although I haven’t tried it on versions of python higher than 2.6.1).

Using gpssig.py takes two steps: first configure your Mail client to take a signature from a file, and then configure gpssig.py to run automatically to update that file.

Thunderbird is relatively easy to set up with an HTML signature. Because it only supports one signature per account, you simply need to tell it to draw that signature from a file. Under each account’s settings there’s an option to “Attach the signature from a file” (see here for a detailed howto). I chose to use ~/.signature.html, but you can use any file you’d like to, just remember the location you choose.

Mail.app is a more finicky beast — although the script supports it, I recommend using Thunderbird, mainly because Mail only refreshes its signatures from files on every launch, whereas Thunderbird will read the file each time you compose a message. However, if that limitation is acceptable (if you don’t move very much, perhaps), it will work just fine. The main issue with Mail.app is that it doesn’t store signatures in an HTML file, but instead in the proprietary .webarchive format. These files can be found in ~/Library/Mail/Signatures. To use gpssig.py with Mail, you need to follow steps 4&5 from http://bytes.com/topic/macosx/insights/825900-setup-html-signatures-apple-mail-mail-app. First create a new signature (under Preferences->Signatures). This will create a new file in the signature folder — take note of the file name. You will use this file name to configure gpssig.py.

gpssig.py is configured with command line options:

Usage: gpssig.py [options] NAME FILENAME
Note: NAME should be enclosed in quotes, unless it contains no spaces.

Options:
  -h, --help   show this help message and exit
  --no-gps     don't attempt to get coordinates from GPS
  -a, --amail  generate files for Apple's Mail.app (.webarchive)
  --lat=LAT    default latitude, if GPS is unavailable
  --lon=LON    default longitude, if GPS is unavailable

The simplest way to use it is manually — simply running it whenever you want to update your signature. For example, I use ./gpssig.py –lat=41.752 –lon=-111.793 ‘Seth Just’ ~/.signature.html to generate a signature for Thunderbird.

If you want to make this automatic, you’ll need to have the script run automatically. On OS X you’ll need to use launchd, while on linux you need cron. Both of these make setting up repeating actions very easy — see here for information on launchd and here for information on cron.

Sadly I haven’t yet figured out a way to run the script whenever you write an email — if I figure it out, I’ll be sure to post something.

The Script

gpssig.py is built around three major functions — one gets coordinates from GPSd, one gets geographical feature information from

The function I use to get GPS information is a bit hacky — there doesn’t seem to be terribly much documentation on GPSd’s python bindings, so I made do with what I could figure out:

class NoGPSError (Exception): pass
 
def get_lat_lon():
  # GPSd Python bindings
  import gps
 
  # Create GPS object
  session = gps.gps()
 
  # Set GPS object as an iterator over reports from GPSd
  session.stream(gps.WATCH_ENABLE|gps.WATCH_NEWSTYLE)
 
  # Loop until we get a report with lat and lon. The limit of 5 loops should be more than enough -- my gps never takes more than three when it has a lock
  i = 0
  while (1):
    try:
      session.next()
      lat, lon = session.data['lat'], session.data['lon']
      break
    except:
      if (i > 5): raise NoGPSError 
      i += 1
 
  return lat, lon

The other function is more straightforward — it makes two http requests to GeoNames.org to get the nearest geographical feature and locality. It then combines those responses in a way that should provide a good response almost anywhere in the world (provided that GeoNames has good, local data). I’ve tested it with a variety of coordinates (provided by http://www.getlatlon.com/), and the responses seem to be pretty good.

def get_geo_string(lat, lon):
  # Modules for REST/XML request from GeoNames
  import urllib
  from xml.etree import ElementTree as ET
 
  # Request the name of the nearest geographical feature
  placename = ET.parse(
      urllib.urlopen("http://api.geonames.org/findNearby?lat=" + str(lat) + "&lng=" + str(lon) + "&featureClass=T&username=sethjust")
      )
  subdiv = ET.parse(
      urllib.urlopen("http://api.geonames.org/countrySubdivision?lat=" + str(lat) + "&lng=" + str(lon) + "&username=sethjust")
      )
 
  # Format and return place, region, country
  try:
    country = subdiv.getiterator("countryName")[0].text
  except:
    try:
      country = placename.getiterator("countryName")[0].text
    except:
      country = ''
  try:
    region = subdiv.getiterator("adminName1")[0].text
  except:
    region = ''
  try:
    name = placename.getiterator("name")[0].text
  except:
    name = ''
 
  if country:
    if region:
      if name:
        result = "%s, %s, %s" % (name, region, country)
      else:
        result = "%s, %s" % (region, country)
    else:
      if name:
        result = "%s, %s" % (name, country)
      else:
        result = country
  else:
    result = "unknown"
 
  return result

Finally, the main method of the program parses arguments, determines what coordinates to use, gets the geographical feature string, and then generates the proper HTML and copies it into the correct place.

if (__name__ == "__main__"):
  # Parse command line options
  from optparse import OptionParser
  parser = OptionParser("Usage: %prog [options] NAME FILENAME\nNote: NAME should be enclosed in quotes, unless it contains no spaces.")
  parser.add_option("--no-gps", action="store_true", dest="nogps", default=False, help="don't attempt to get coordinates from GPS")
  parser.add_option("-a", "--amail", action="store_true", dest="amail", default=False, help="generate files for Apple's Mail.app (.webarchive)")
  parser.add_option("--lat", action="store", type="float", dest="lat", help="default latitude, if GPS is unavailable")
  parser.add_option("--lon", action="store", type="float", dest="lon", help="default longitude, if GPS is unavailable")
 
  options, args = parser.parse_args()
 
  try: assert(len(args) == 2)
  except AssertionError:
    print "You must provide NAME FILENAME\n"
    parser.print_help()
    exit()
 
  try: assert(((options.lat!=None) & (options.lon!=None)) | ((options.lat==None) & (options.lon==None)))
  except AssertionError:
    print "You must provide both lat and lon arguments\n"
    parser.print_help()
    exit()
 
  # Modules for creating signature file
  import tempfile, os
 
  try:
    if (options.nogps): raise NoGPSError
    lat, lon = get_lat_lon()
    print "Got %f, %f from gps" % (lat, lon)
  except NoGPSError:
    if (not options.nogps): print "Failed to get coordinates from GPS"
    try:
      assert((options.lat!=None) & (options.lon!=None))
    except AssertionError:
      print "No default coordinates provided; exiting"
      exit()
    lat, lon = options.lat, options.lon
    print "Using %f, %f as coordinates" % (lat, lon)
 
  geostring = get_geo_string(lat, lon)
 
  lac, loc = 'N', 'E'
  if lat < 0:
    lat *= -1
    lac = 'S'
  if lon < 0:
    lon *= -1
    loc = 'W'
 
  file = tempfile.NamedTemporaryFile()
 
  file.write("<html><body>\n<p>")
  file.write(args[0])
  file.write("</p>\n<p>")
  file.write("Current meatspace coordinates, hot from the GPS receiver card in my laptop:")
  file.write("</p>\n<p>")
  file.write("%.3f %s latitude, %.3f %s longitude" % (lat, lac, lon, loc))
  file.write("</p>\n<p>")
  file.write("Nearest geographical feature: " + geostring)
  file.write("</p>\n")
  file.write("</html></body>\n")
 
  file.flush()
 
  if (options.amail):
    os.system("textutil -convert webarchive -output " + args[1] + " " + file.name)
  else:
    os.system("cp " + file.name + " " + args[1])

Two and a half years ago, GPSd had just released version 2.38. The latest version, which I just downloaded, is 2.96. Most significantly, GPSd has updated their communication protocol from a simple character-command format to one based on JSON-packed data. Further, they’ve built a significant portion of the project around python, and consequently built better python interfaces into the project.

OS X has also been updated, from whatever 10.5.x was current three Januaries ago, to 10.6.8. Luckily, the under-the-hood changes that Snow Leopard brought to the table should only make compiling software easier.

Building GPSd is a whole lot easier than it was the last time I went through all of this. I downloaded the latest source package (from http://prdownload.berlios.de/gpsd/gpsd-2.96bis.tar.gz). The bundled INSTALL file lists only python and py-gtk2 as dependencies, which makes compilation easy, given that python comes bundled with OS X. Although py-gtk2 is available through MacPorts (using sudo port install py-gtk2) I chose to avoid install the ridiculously long list of dependencies that it requires, as it is only required for the graphical test client (xgps), and GPSd also ships the perfectly functional command-line tool cgps, which provides the same information, albeit in a more sparse manner.

The actual build process is surprisingly easy: I ran ./configure –x-includes=/usr/X11R6/include, as suggested by the INSTALL file. As this indicated no issues, I ran make and sudo make install, which ran without a hitch, and gave me a working set of gps tools.

At this point it is possible for me to attach my GPS (see my old post for information about getting devices up and running), run gpsd -n /dev/cu.usbserial, and then use cgpsto get coordinates, date, and satellite information. However, this isn’t everything — all of the python based GPSd tools, such as gpsprof, still don’t work. This is because of Apple’s slightly special python distribution — while GPSd’s sudo make install puts python modules into /usr/local/lib/python2.6/site-packages/, they need to be in /Library/Python/2.6/site-packages/. Instead of having to install these manually, you can use the bundled python install script to put the modules in the correct path by running sudo python setup.py install (thanks to http://docs.python.org/install/index.html).

Now that I have the most recent GPSd up and running I’m hoping to do some fun things with it. If I do, you’ll see it here!

I noticed that I was able to load the website just fine in Safari, and that’s when I had an insight — I noticed that Safari was loading http://grooveshark.com, while Chrome was taking me to https://grooveshark.com. It turns out that the issue was with a plugin I use — the KB SSL Enforcer. While it’s a great piece of software, it was forcing Chrome to connect to the SSL site, which for some odd reason was causing the blank page to be displayed.

The fix for this issue was easy. I just opened up the SSL Enforcer options and added grooveshark.com to the blacklist; telling the plugin to never force SSL for Grooveshark.

Now I’m happily listening to tunes online without having a second browser open!

In September 2010, Hans Viksler posted an article about the insecurity of the stored-value smart card system used by Web Laundry (now Wash Laundry). I’ll let that article stand on its own — it gives a good overview of the bone-headed system that the engineers there had in place. In short, they used a secure memory card made by Atmel (specifically, from the CryptoMemory line), the AT88SC0404C (datasheet here), but neglected to change the default master password. This means that all you need to read or write the stored data is a ISO-7816-3 compliant smart card reader.

This is where my story starts — this summer I’m living in a dorm that uses a Web Laundry stored value system. That was enough of a push for me to buy a smart card reader, seeing as I’d always wanted to play with them, and this looked like a good opportunity. I picked up a smart card reader from Amazon.com, an SCM Microsystems SCR3310. It was both cheap and, according to the manufacturer’s product page, offers full ISO 7816, CCID and PC/SC compatibility (i.e. all of the relevant standards), as well as drivers for OS X, which is my primary operating system for the time being.

Doing some research, it turns out that Apple ships a (modified) version of the open-source PCSC Lite framework for smart card integration. This means that all I would need to get up and running was a driver for my device and a way to interface it. Once the reader arrived I installed the drivers, and ran pcsctest (from PCSC Lite) on the command line. Sadly, all I got was an error message:

Testing SCardEstablishContext    : Service not available.

Googling told me that the appropriate services are supposed to start whenever a smart card reader with appropriate drivers is plugged in, which made this error all the more confusing. Luckily, I found this thread on SCM’s forums — it seems that the driver they have posted doesn’t include the USB identifiers for the version of the reader I had, but a helpful poster left instructions to modify a plist file in the driver (mirrored here for archival purposes). With that, I was up and running!

pcsctest spat out useful output this time around:

$ pcsctest

MUSCLE PC/SC Lite Test Program

Testing SCardEstablishContext    : Command successful.
Testing SCardGetStatusChange
Please insert a working reader   : Command successful.
Testing SCardListReaders         : Command successful.
Reader 01: SCM SCR 3310 00 00
Enter the reader number          : 1
Waiting for card insertion
                                 : Command successful.
Testing SCardConnect             : Command successful.
Testing SCardStatus              : Command successful.
Current Reader Name              : SCM SCR 3310 00 00
Current Reader State             : 0x34
Current Reader Protocol          : 0x0
Current Reader ATR Size          : 8 (0x8)
Current Reader ATR Value         : 3B B2 11 00 10 80 00 04
Testing SCardDisconnect          : Command successful.
Testing SCardReleaseContext      : Command successful.

That left me with the issue of interacting with the smart card somehow. In case you hadn’t guessed from the post title, that solution was Python. Specifically, the pyscard bindings for PCSC Lite, from pyscard.sourceforge.net. There’s a nice array of examples, and so I wrote up a python script for interacting with this particular CryptoMemory card, based on the command set from the datasheet and the examples. It’s not as polished or feature-rich as the software Hans posted, but if you’re running OS X or Linux, it should be helpful. At the moment this script is extremely rough — it gets the job done, but in an ugly and unsafe way. I’m posting it here, but you SHOULD NOT USE IT IF YOU DON’T KNOW WHAT YOU’RE DOING. If you aren’t careful, it will mess up your card. Hopefully I’ll have time to wrap it all in a library that will abstract away the messiness and provide nice features like exception handling; if I do, you’ll see it here.

Using my script I was able to verify Hans’ findings — although the card is configured to require cryptographic authentication to access the user zones (where the goodies can be found), the password is left at the default value, which makes overwriting the access registers and conducting a replay attack (as demonstrated by the video in his post) a walk in the park. Following his example, I won’t post any information on how the cards store their values, but it’s surprising that this security hole still isn’t fixed, seeing as it would cost nothing to overwrite the master password when they first configure the cards.

Hopefully this post will give some of you who’ve wanted to work with smart cards a push in that direction — although there are a few hurdles along the way, it’s an interesting area to work on. I’m hoping to move on from poking at other people’s cards and start using my new hardware for authentication and encryption.

Happy hacking!

My goal for this post is to record my process in putting this project together. I’m nowhere near done at the moment, but I’ll keep updating it as I go.

Planning

The plan for this project came together slowly – I knew that I wanted to make a large RGB LED display, and I had already bought one light strip to play with a year or so ago. I’m not sure how the Rainbowduino came across my radar, but it seemed perfect, because it could drive up to 64 RGB LEDs simultaneously, so could support up to 6 strips. However, the funding for the project chose to use 3, and I felt that that was more than enough to get the effect I was shooting for.

Because the strips run at 12 volts, and are each rated for 6 amps, I decided to use a spare PC power supply to provide power because it supplies a well-regulated voltage and plenty of current.

Finally, the Rainbowduino can operate in one of three ways: standalone mode, serial mode, or I2C mode. The second and third allow you to stream patterns to the Rainbowduino from another microcontroller or computer. However, I want this sun to stand on its own, so I’m planning on having it run in standalone mode. This means I’ll need a way of programming it with whatever patterns I want it to use. The Rainbowduino has a 6-pin ICSP plug, which will work perfectly with the AVR programmer I already have, Lady Ada’s UsbTinyISP.

Preparation

To prepare for putting the whole display together, I wanted to test my LEDs, power supply and control board. I used an RGB driver based on a Teensy 2.0, a few FETs and a wall-wart (which I know works well with these strips) as a simple tester for the LEDs, and found no problems. The power supply also checked out, I took apart a single 4-pin plug to get the +12V and GND wires and checked the voltage with a multimeter. The reading was good and steady, but attaching it to the Rainbowduino caused one of the power-filtering capacitors to explode (which was unexpected, given the board is rated for 12V), but removing the damaged cap fixed the problem, and soon I had it powered up and lighting LEDs. I also connected the UsbTinyISP and used Avrdude to ensure I could program the Rainbowduino. (As an aside, the Avrdude part name for the ATMEGA328P is ‘m328p’, which took me way too long to figure out).

At this point I felt comfortable that I had everything I needed to put the display together (except for some sort of mounting board. However, the end of the weekend was drawing to a close, so I had to wait to get more done.

Steeling Myself

Before I prepared to cut my 3 strips into 30 smaller ones, and soldered 4 wires to each one, I decided to get a picture of what the final wiring would look like. This was a job for Cadsoft’s Eagle, the defacto-standard for making schematics and PCB layouts. Even though I’m planning on laying out the display by hand, with wires, I felt that having a reference for wiring the matrix would be worthwhile. I built a schematic to show the control layout for the LEDs, as a matrix, which is what the Rainbowduino is designed to drive. I then built a layout based on the schematic that corresponds (roughly, and not to scale) to how I’m planning to arrange the LED strips, although the footprints of all the parts are completely arbitrary. However, the pin layout of the headers on either side match the layout of those on the Rainbowduino, which will make it helpful when it comes time to connect all 120 wires.

Wiring

Update, May 2: I’ve now finished wiring the matrix: I attached all of the strips to a piece of foamcore board using their adhesive backing and soldered all of the connections. Everything worked on the first try, and I flashed the code (rainbowduino_v1_0_4) from here. The demo patterns looked amazing, but sadly, shortly after powering it up (before Icould even get a video), something stopped working. Not only were the patterns not being displayed, but I couldn’t get my programmer to connect to the rainbowduino! Luckily, I emailed SeeedStudio, and one of their very helpful employe has promised me that a replacement is already on the way. Hopefully it arrives before the fifth, when I was hoping to set up the display on campus. Until it arrives, and I can replace the defective board on the display, enjoy the only two photos I took while it was working (before I flashed the new firmware onto it).

Final words

Despite the setback with my Rainbowduino, I went ahead with getting the display ready for this weekend, where (hopefully) it will be sitting in a central place, entertaining people with colorful patterns. To do this, I used a large zip-tie to strap the ATX power supply to the back of the piece of foamcore board, and used some more zip ties to position all of the wires out of sight, as well as to securely fasten the two wires running 12V to the display. All in all it looks good, and I’m excited to load some exciting patters onto it once my new control board arrives.

Also, this post is still in progress — check back soon for updates! Apologies for the lack of photos, they should be coming soon.

hidefocus="true"

attribute to the submit button. I did this, and everything worked beautifully.

It is now replacing an older, wireless, but more compact keyboard from the same company, which, despite serving me well, had been getting flaky in age.

Hit the jump for another picture and a review/comparison of the two keyboards

As I said, this keyboard is replacing my old wireless one, and offers several advantages over it. The first thing I noticed after taking it out of the box was the size: the new one is considerably bigger, allowing it room for a full, proper numpad and, arrow keys, and Home/End/PgUp/PgDn/Ins/Del keys that need a Fn key on the old keyboard.

The second major difference is the new key design, which they call “chocolate key”. It’s the same design as Macbook keyboards, with flat keys shaped like rounded rectangles. The combination of a new key design and layout mean that the new keyboard is a lot roomier — my hands don’t feel cramped and can move freely.

The last thing I noticed quickly after getting the new keyboard set up is the feel of the keys. While the old, wireless keyboard has the mush feel of most laptop keyboards, the new key design has a much crisper feel and a more “clicky” feel, even though it still uses scissor-style key switches. While this makes typing slightly louder, it feels much nicer, and makes typing more enjoyable and responsive.

In all, the new keyboard is a welcome update. However, it won’t completely replace the old one. The biggest reason is the wireless keyboard’s range: because it will work anywhere within hearing range of the computer, I use it as a remote control for my music player.

The source code of the script used to generate the images is available here.

Get the code here.

It turns out that the scanner emulates a PS/2 keyboard and will read almost any 1D or 2D barcode symbology. After a few hijinks with a loose ribbon cable and flaky PS/2 support on my computer I got the scanner working perfectly. I was even able to change its configuration by scanning barcodes from the manual displayed on my LCD (though I don’t know if it will work with glossy screens — mine is matte).

I’m planning on putting up a more complete summary of what I’ve found, but here are a few other things that caught my eye:

• A solenoid-controlled proportional valve for small pneumatics or hydraulics.
• A bag of large rubber grommets, one of which I cut up to replace the feet on a table lamp.
• Three matched stepper motors.
• A worm-gearbox connected to a large motor with integrated optical encoder.
• A wide variety of IR LED/phototransistor gates.
• A pile of 1.8V, 2.5V and 3.3V voltage regulators.

Stay tuned for pictures and more details on what I’m taking and what I’m going to do with it.

To make a long story short, I was recently offered a chance to receive one of these migratory lending libraries, so expect to see something in this space about it soon.

$ time python mandel.py > \dev\null
real	0m0.051s
user	0m0.036s
sys	0m0.010s
$ time perl mandel.pl > \dev\null
real	0m3.518s
user	0m3.463s
sys	0m0.029s

You can find the code here.

This script works well for zooms, as long as you stay below a few thousand iterations. The following picture was generated with x=-1.1887204, y=-0.3032472, width=0.01 and 150 iterations.

After the jump, I’ll give you the code and explain how it all works.

How it Works:

The code from ~/.conkyrc that makes this calendar is simple:

Edit: I’ve updated the code as Zacco suggested in the comments to fix a minor bug on certain dates.

${color orange}CALENDAR ${hr 2}$color
${execpi 60 DJS=`date +%_d`; cal | sed s/"\(^\|[^0-9]\)$DJS"'\b'/'\1${color orange}'"$DJS"'$color'/}}

This is a somewhat complicated expression, but what it does is fairly simple. The first line simply draws the title for the section, and it’s the second line that does the magic. Let me break it down and explain it.

${execpi 60

This command tells Conky to execute the next argument every 60 seconds, and, importantly, parse the output of that argument. This way, when we put in commands that change the text color, Conky will obey them instead of printing them.

DJS=`date +%_d`;

DJS (which stands for “date” followed by my initials) is a temporary variable that holds the current day of the month, padded with a leading space, if necessary (so that we’ll catch the first of the month, not every 1 in the calendar, for example).

cal |

cal simply prints out a simple calendar, and the pipe feeds that output through to the next commmand:

sed s/"\([^0-9]\)$DJS"'\b'/'${color orange}'"$DJS"'$color'/
This is one big mess of a command, but the main body is a regex that sed takes as an argument. The regex searches for the string “\([^0-9]\)$DJS”‘\b’, which means the contents of the variable DJS (which we set earlier) preceded by anything other than a digit, and followed by a word boundary – a change from printable characters to white space. This means that it will find the current date (one or two digits) but won’t find the 3 of the 30th on the third of the month. It also means that it will work correctly if the current date is on the far left or right column of the calendar.
The second half of the regex simply wraps what it found the first time around in a couple of Conky commands that change to color to orange, and then back to what it was before.
Lastly, the closing bracket (}) at the end of the line closes out the opening one that is required for all Conky commands with arguments.
Now go forth and cover your desktop in beautiful calendars.
Update: Erik in the comments has a modification to center the entire calendar, if left-aligning isn’t for you.
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		Mon, 30 Mar 2009 02:10:31 +0000
		sethjust
				
		
		
		
		
		
		
		

		http://sethjust.wordpress.com/?p=74
		
			So I had the wonderful experience this weekend of losing over 1,200 words of work on a paper because I forgot to save it regularly. I was really, really sad about that and really bummed that Pages, my word processor of choice (I love the formatting tools), doesn’t support either autosaving or document recovery. However, my preference for Pages is strong enough that I didn’t jump ship to an auto-saving editor. Instead I went out and found WorkSaver. 

Worksaver simply sits in your menubar and, at a definable interval will save every iWork document you have open, provided that it’s already been saved once. This means that when I’m writing I don’t have to even worry about saving my document after creating it and choosing where to save it. Of course, it’s a shame that you have to manually save the file when you create it, but it’s a lot better than losing all your work. I can highly recommend WorkSaver if you use iWork simply for the peace of mind it provides. Of course, it’s not perfect for everybody, but when I’d rather focus on writing a paper than on making sure my computer doesn’t decide to make it all go away, WorkSaver is just what I need.

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		Wed, 25 Mar 2009 02:39:05 +0000
		sethjust
				
		
		
		
		
		
		
		
		
		
		

		http://sethjust.wordpress.com/?p=65
		
			I’ve been getting into a mood lately that makes me fiddle around with fun Perl stuff, but sadly school’s picking up to the point that writing anything up isn’t going to happen. However, I have a couple short scripts that I’m just dying to share.

Just Another Perl Hacker
I figured that it was about time in my hacking career (read: I was bored enough) that I should make a japh script. After a couple attempts I came up with this:

#!/usr/bin/perl
while(<DATA>){
 	for (map{ord($_)-33}split ''){
		$__++;
		$_||(print(chr($__+19))&&($__=0));
	}
}
 
print "\n";
 
__END__
                   /|                        |\
      !            ; :                        : :
                  | Y,                      ,P |
     !             |  Yb.        __        ,dP  |
                  l\  YMMb,_ _,/  \,_ _,dMMP  /f
  !                 j;  `YMMP'  `--'  `YMMP'  ;j
                   : \   YP`-._    _.-'YP   / ;
  !            !      \ `\,  _,\_    _/,_  ,/' /
                     `,_,   \`o>  <o'/   ,_,!'
                         `\            /'
                           |  _    _  |
      !                     / 88b  d88 \
                           \ `8P  Y8' /``-.
             !               `\,    ,/      \
                             _`----'        \
                  !        _.'/ '          `, \
                        .'_,'_..._          \ ;
       !               .',/.dMMMMMMb. |      /  \
                    .'./.MMMMMMMMMMM ; !    /    ;
                   / /.MMMMMMMMMMMMM/     /     ;
                  | ;dMMMMMMMMMMM!P/'   ,/'   !    ;
                  |/dMMMMMMMMMP'     .'          |
   !               ;dMMMMMMMMM|     _/            |
                 ;dMMMMMMMMMMb_|_!| /;            ;\,
                 dMMMMMMMMMMMM`M`M`;.---..      '   `\,
                :M!MMMMMMMMMMMMMMMP/'     `\            \
               /|MMMMMMMMMMMMMMP/          \    _!_      `.
  !            / |MMMMMMMMMMMMMM|            |.-'  `-._    \         .'\
             ;!  ;MMMMMMMMMMMMMM|            :         `-._ `-.     /  _\
             |   ;!MMMMMMMMMMMMM;            |             `-. `-.._.'/
              \   `\YMMMMM!MMMP/'\           |                `~~----'
               `-._, ``YMMMP'_.-'\         ! ;_
                 |      /         `-.,_./     7
                _/    `\,    !        /      _/
             ,-' ,  ,   /         _.'      /
            (_(_(__(__.'       !,-'        /
                              (__(__(_(_/'

Download.
I’ll let you go ahead and figure it out on your own. It’s not super-hard, but it’s fun.
Mandelbrot
In another fit of boredom I decided that it was finally time to create a mandelbrot set renderer. I originally tried to make one of these in basic, long before I had the math to do so. I was proud that I got the real axis to render, and figured it was time to complexify it. To keep things simple I decided to make it render an ASCII-art version of the set that would fit in a terminal window. The output looks like this:
                        ...............................:::::oo@@@@o::::..........
                      ...............................::::::O@@@@@@@@o:::::.......
                     .............................::::::::oO@@@@@@@@o::::::::....
                   ...........................::::OOO8ooO@O88@@@@@@8@O8o::::Oo:..
                  .......................:::::::::o8@@@@@@@@@@@@@@@@@@@@OO@@@@::.
                 ...................:::::::::::::oOO@@@@@@@@@@@@@@@@@@@@@@@@@o:::
                ................:::::::::::::::o@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo:::
               ..............::::@oo::oOoo:::ooo@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@8o:
               ...........:::::::oO@@@O@@8@OooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@O::
              ..........:::::::::oO@@@@@@@@@@88@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@::
              ........:::::::8ooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o::
              .:::::::::::::oO@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o:::
              @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo::::
              .:::::::::::::oO@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o:::
              ........:::::::8ooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o::
              ..........:::::::::oO@@@@@@@@@@88@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@::
               ...........:::::::oO@@@O@@8@OooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@O::
               ..............::::@oo::oOoo:::ooo@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@8o:
                ................:::::::::::::::o@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo:::
                 ...................:::::::::::::oOO@@@@@@@@@@@@@@@@@@@@@@@@@o:::
                  .......................:::::::::o8@@@@@@@@@@@@@@@@@@@@OO@@@@::.
                   ...........................::::OOO8ooO@O88@@@@@@8@O8o::::Oo:..
                     .............................::::::::oO@@@@@@@@o::::::::....
                      ...............................::::::O@@@@@@@@o:::::.......
                        ...............................:::::oo@@@@o::::..........
The code’s far from polished and not what I like to publish, but it’s a fun thing to look at and offers you some neat abilities to poke things around and fix some pesky problems that just need clear thinking applied to them. It’s available here.
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		Thu, 12 Mar 2009 03:44:45 +0000
		sethjust
				
		
		
		
		
		
		

		http://sethjust.wordpress.com/?p=57
		
			So the other day I finally got tired with my (awesome) wallet and decided to make something new. I ended up choosing a money clip. Not only would it be a nice, high quality, metal object living in my pocket, instead of a crummy, dirty wallet, but a money clip is good looking, classy and minimalistic way of keeping a hold of my money and cards. Looking around my room I didn’t really get any inspiration, until I saw an old metal fork lying in a box. I cut the head off with my dremel and a fiberglass cutting wheel. A little bit of sanding and bending resulted in a, super-useful money clip. I’ve been using it for the past few days and it’s been serving me really well, looking good, and altogether holding up like a quality product.







If there’s interest, I’ll put up more information / pictures and maybe put some of these bad boys up for sale.
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