Archive for the ‘Innovation’ Category

Integrated subproject sites on

Saturday, January 14th, 2017

This has been bothering me for a few years now, but in the FAQ for readthedocs it calls out the celery/kombu projects as an example of subprojects on RTD. And.. ok, I suppose it’s technically true, they are related projects, and they do use the subprojects. But if you didn’t know that kombu existed, you’d never be able to find it from the celery project. But they aren’t good examples, and as far as I can tell, no large project uses subprojects in an integrated/useful/obvious way.

Until I did it in December, anyways.

Now, one problem RobotPy has had is that we have a lot of subprojects. There’s robotpy-wpilib, pynetworktables, the utilities library, pyfrc… and until recently each one had it’s own unique documentation site, and there was some duplication of information between site. But it’s annoying, because you have to search all of these projects to find what you want, and it was difficult to discover new related content across projects.

However, I’m using subprojects on RTD now, and all of the subproject sites now share a unified sidebar that make them seem to be one giant project. There are a few things that make this work:

  • automatically generate the sidebar, which means the toctree in all of the documentation subproject sites are the same.
  • They use intersphinx to link between the sites
  • But more importantly, the intersphinx links and the sidebar links are all generated based on whether not the project is ‘stable’ or ‘latest’.

The last point is really the most important part and requires you to be a bit disciplined. You don’t want your ‘latest’ documentation subproject pointing to the ‘stable’ subproject, or vice versa — chances are if the user selected one or the other, they want to stay on that through all of your sites. Thankfully, detecting the version of the site is pretty easy:

# on_rtd is whether we are on, this line of code grabbed from
on_rtd = os.environ.get('READTHEDOCS', None) == 'True'

# This is used for linking and such so we link to the thing we're building
rtd_version = os.environ.get('READTHEDOCS_VERSION', 'latest')
if rtd_version not in ['stable', 'latest']:
    rtd_version = 'stable'

Then the intersphinx links are generated:

intersphinx_mapping = {
  'robotpy': ('' % rtd_version, None),
  'wpilib': ('' % rtd_version, None),

And  as a result, they point to the correct version of the remote sites, as do the sidebar links.

While this approach may not work well for everyone, it has worked really well for the RobotPy project. Feel free to use this technique on your sites, and check out the RobotPy documentation site at!

GTK3 Composite Widget Templates for Python

Sunday, May 24th, 2015

Recently, the other developers of the Exaile audio player and I decided to finally migrate to GTK3 and GStreamer 1.x. I mentioned that I wanted to use some code I had developed a few years ago to get rid of the manual UI building code that we had and replace it with GtkBuilder XML files, and @mathbr noted that GTK had added a new feature called ‘composite widget templates’ a few years ago. The ideas were similar to mine, and reading the comments in a blog post about the Vala implementation inspired me to create a working version of this for Python. The first implementation took a few hours, and I’ve been adding improvements ever since as I’ve been integrating this into Exaile.

Here’s how the vala demo code from that blog post looks like in Python, turns out it’s not *that* different:

from __future__ import print_function
from gi.repository import Gtk
from gi_composites import GtkTemplate

class MyWidget(Gtk.Box):

    __gtype_name__ = 'MyWidget'
    entry = GtkTemplate.Child()

    def __init__(self, text):
        super(Gtk.Box, self).__init__()
    def button_clicked(self, widget):
        print("The button was clicked with entry text: %s" % self.entry.get_text())

    def entry_changed(self, widget):
        print("The entry text changed: %s" % self.entry.get_text())

The key pieces to note are:

  • Use the @GtkTemplate decorator to load the template for your widget
  • Use GtkTemplate.Child to create attributes on your widget that will be loaded from the XML file (there’s also GtkTemplate.Child.widgets(n) if you need to declare multiple widgets)
  • Use @GtkTemplate.Callback decorator to mark methods to be connected to signals as declared in the XML file

For the full demo + associated GtkBuilder XML file check out the github repo.

I’d love to see this functionality included with GTK’s python bindings, and in fact after creating this I found a bug open on the GNOME bugzilla with a patch to PyGObject to allow python users to use it, but for whatever reason it never got merged. My implementation works on the current release of PyGObject, and possibly older versions too.

Want to get rid of boilerplate in your GTK3 python application? Check out the examples/code on github.

Award Winning FIRST Robotics Robot Control Interface

Monday, April 8th, 2013

KwarqsDashboard is an award-winning control system developed in 2013 for FIRST Robotics Team 2423, The Kwarqs. For the second year in a row, Team 2423 won the Innovation in Control award at the 2013 Boston Regional. The judges cited this control system as the primary reason for the award.

It is designed to be used with a touchscreen, and robot operators use it to select targets and fire frisbees at the targets. Check out the shiny screenshot below:

Kwarqs Dashboard ScreenshotThere are a lot of really useful features that we built into this control interface, and once we got our mechanical and electrical bugs ironed out the robot was performing quite well. We’re looking forward to competing with it at WPI Battle Cry 2013 in May!  Here’s a list of some of the many features it has:

  • Written entirely in Python
    • Image processing using OpenCV python bindings, GUI written using PyGTK
    • Cross platform, fully functional in Linux and Windows 7/8
  • All control/feedback features use NetworkTables, so the same robot can be controlled using the SmartDashboard instead if needed
    • SendableChooser compatible implementation for mode switching
  • Animated robot drawing that shows how many frisbees are present, and tilts the shooter platform according to the current angle the platform is actually at.
  • Allows operators to select different modes of operation for the robot using brightly lit toggle switches
  • Operators can choose an autonomous mode on the dashboard, and set which target the robot should aim for in modes that use target tracking
  • Switches operator perspective when robot switches modes
  • Simulated lighted rocker switches to activate robot systems
  • Logfiles written to disk with errors when they occur

Target acquisition image processing features:

  • Tracks the selected targets in a live camera stream, and determines adjustments the robot should make to aim at the target
  • User can click on targets to tell the robot what to aim at
  • Differentiates between top/middle/low targets
  • Partially obscured targets can be identified
  • Target changes colors when the robot is aimed properly

Fully integrated realtime analysis support for target acquisition:

  •  Adjustable thresholding, saves settings to file
  • Enable/disable drawing features and labels on detected targets
  • Show extra threshold images
  • Can log captured images to file, once per second
  • Can load a directory of images for analysis, instead of connecting to a live camera

So, as you can see, lots of useful things. We’re releasing the full source code for it under a GPL license, so go ahead, download it, play with it, and let me know what you think! Hope you find this useful.

A lot of people made this project possible:

  • Some code structuring ideas and PyGTK widget ideas were derived from my work with Exaile
  • Team 341 graciously open sourced their image processing code in 2012, and the image processing is heavily derived from a port of that code to python.
  • Sam Rosenblum helped develop the idea for the dashboard, and helped refine some of the operating concepts.
  • Stephen Rawls helped refine the image processing code and distance calculations.
  • Youssef Barhomi created image processing stuff for the Kwarqs in 2012, and some of the ideas from that code were copied.

The included images were obtained from various places:

  • Linda Donoghue created the robot image
  • The fantastic lighted rocker switches were created by Keith Sereby, and are distributed with permission.
  • The green buttons were obtained via google image search, I don’t recall where

Download it on my FRC resources page!

Notepad++ plugin to enable unindent on backspace key

Monday, December 3rd, 2012

When I first started using editors, I was a tabs person. I always set the tab size to 4 since I liked the way that looked, and used tabs instead of spaces. And it wasn’t really a philosophical reason behind it, it was very simple actually:

I really hate hitting backspace 4 times to unindent

Seems simple enough. Yes, I know you can use SHIFT-BACKSPACE or other voodoo to make it work, but I want to hit *one* key.

Because of this, I always used 4-space tabs instead of inserting spaces instead of tabs. However, at some point I started writing a project in python, and python tends to encourage spaces vs tabs. Notepad++ is my favorite editor, so I decided to write a plugin for Notepad++ to make using spaces a lot less annoying — and in particular, to make it so that when I hit backspace, it would magically eat the spaces back to the next indentation level.

In the process of trying to do this, I discovered that the Scintilla editing component actually has this functionality built-in — you just need to enable SCI_SETBACKSPACEUNINDENTS on the editor component. So I took the sample plugin for Notepad++ and added two lines of code that enabled this functionality, and it works great! Ever since then, I’ve used spaces instead of tabs, since I really can’t tell the difference — and that’s how I like it 🙂

I actually wrote this thing a rather long time ago, and never got around to actually cleaning it up and releasing it. I’ve decided to release it in its present form, since it’s so useful and very simple. It would be even better if Notepad++ had an option to enable this, but this works just as well until that happens.

This plugin is known to work in versions of Notepad++ since 4.x, and works in Notepad++ running under Wine also. Download the Notepad++ tabs plugin at my usual software page.

Use GroupTagger to rapidly organize your audio files with Exaile 3.3.0 using the Grouping tag

Saturday, October 6th, 2012

Well, I haven’t blogged here in quite awhile, but it’s been a pretty busy year! One project I’ve been spending a fair amount of time on is Exaile, a cross platform music player for GTK+ (its free and works on Windows, Linux, and even OSX — though, the installation for OSX is rather tricky). I’ve been DJ’ing Lindy Hop dances for almost a year now, and I’ve been fixing up Exaile to be an awesome music player for DJing — adding a BPM counter, secondary output device support (sometimes called pre-listening), and other things that I’ve found to be useful.

One feature in particular I want to highlight is a plugin I’ve created called GroupTagger. This super-useful plugin is distributed with the latest stable version of Exaile. This plugin allows you to easily and rapidly organize your music using the ‘Grouping’ tag in your audio files. The best part about this is that the data is stored in your MP3/OGG/FLAC/whatever audio files, so you can use the data with your favorite audio player if it supports it (Winamp, iTunes, others already do). A lot of people already categorize their music using this tag, and this plugin can manage music that is already tagged this way. To illustrate how useful this is, here are some screenshots and a mini-tutorial.


Changing variables using a web interface and embedded HTTP server

Tuesday, April 21st, 2009

When walking around during the Boston Regional, I had been talking to some people about code, and they mentioned that LabView was great because they could tune their PID controllers on the fly while the robot was operating. So I thought to myself, “why can’t I do this with C++?”. And… so I did. WebDMA was created to allow our FIRST Robotics team to tune our robot in an easy to use and intuitive way via any modern web browser.

Using C++ operator overloading, WebDMA provides proxy objects that your application can use as normal variables which can be manipulated or displayed by your application via a configurable jQuery/javascript powered Web 2.0 interface hosted by an lightweight embedded web server.

Despite that WebDMA was specifically created for use in FIRST Robotics on the NI-cRio/vxWorks platform, it uses the Boost ASIO portable networking library and Boost Thread portable threads library and is usable on any platform supported by these Boost libraries (tested on Boost 1.38, requires a patch for vxWorks).

A non-functional (but very shiny) demo of the interface is available at

Visit the Google Code project site for WebDMA

Update: Go here for a video:

pscanf: a sscanf replacement for C

Wednesday, August 6th, 2008

In general, I like C. Pointers don’t generally bother me all that much, and its really nice to use for a lot of different things. However, its string handling SUCKS (though, printf is nice). It seems like a lot of the string routines in the standard C library are designed to screw you in the most unexpected ways possible.

So recently I’ve been struggling with processing input from a user on the command line, and I was using sscanf to attempt to do really simple string processing, and it simply wasn’t matching the correct things. After much struggling and coming to the realization that I needed to do something similar to regular expressions… I sat down and wrote the following function, and it works quite well for what I want to do.

What it does do:

  • Match arbitrary strings using a perl regex, and return the matches to you

What it doesn’t do:

  • This is not a drop-in replacement for sscanf: you need to change the format string around and (possibly) your parameters.
  • It will not return anything but a string. Thats all you get. Of course, if you format your regex correctly then you can pretty much be guaranteed that strtol/strtod/etc will work…
  • Give you any kind of comprehensive error reporting. If you want that, then just use the pcre functions directly
  • Cook your meals or do your laundry

This is released under the license contained on, enjoy!


SSHFS For Windows

Wednesday, July 9th, 2008

This japanese guy apparently wrote something similar to linux’s FUSE for Windows (supporting user-mode filesystem drivers) and created a number of bindings for it. As a practical example, he’s implemented SSHFS in windows, which is awesome IMHO and exactly what I’ve been looking for.

However, this means someone can now write a filesystem driver in Visual Basic. How awesomely crazy is that?

Go to his site to download SSHFS for Windows.

What can you do with 100 bezels?

Tuesday, May 6th, 2008

I’m always on the lookout for creative opportunities, and my latest endeavor has led me to obtain around 100 of these really neat looking plastic bezels from a local business:

Poweredge R200 Bezel (front)Poweredge R200 bezel (back)

Now, it struck me that there’s a really cool use waiting for these things, however I can’t think of anything compelling at the moment. Some ideas that I have:

  • Creating some table or shelf with them
  • Monitor stands
  • Geeky decorations

However, I’m quite sure that theres much more that can be done with these. So the burning question I ask you is… what should I do with them?

Edit: Some other suggestions I’ve received

  • Coffee table
  • Create some kind of katamari out of the dell logos
  • Duct tape based door of some kind

C# Oscilloscope and Analog Meter Controls

Thursday, April 3rd, 2008

I updated my C# analog meter control awhile ago (it had some bugs), but never got around to posting it online. Well, here are those updates, PLUS I integrated a C# Oscilloscope control as well! I’d put up some screenshots, but I don’t currently have a compiler installed for C# (been redoing my machine) so I can’t take any. But, it works pretty nicely except for a few non-serious bugs….

This is an ongoing set of postings documenting some of the software I developed for my senior project this fall.

Go download it.