Coding a Custom Step Sequencer

I have been wanting to code my own customer step sequencer for a while. A couple of weeks ago I finally dived in to the project. I knew I wanted to use a lightweight scripting language for the project an started out with Python. But after trying out a couple of Midi libraries I got frustrated and switched to Ruby with UniMidi.

UniMidi actually works pretty well, and I was able to write a fairly complete 8 track step sequencer for my Novation LaunchPad Mini in about 20 hours. The source code is available on github.  I also made a track where I used this sequencer to control my Volca Sample, and it worked out great.

Last week I decided to take things a bit further and ordered a Novation LaunchControl from Thomann. I figured this controller would be perfect fit for my needs: The silicon pads can be used to mute/unmute the 8 tracks and the 2 x 8 knobs can be set to control volume and pan of the corresponding Volca Sample channels (I’m actually using the right output on the Volca Sample as an effect send, so the pan knob acts as dry/wet balance).

I made another track with this setup and it worked out great… I will be needing a second LaunchControl for my Volca Beats before long. Or maybe I should get hold of some silicon pads and build a more customised midi controller…

I hit some snags with my Ruby/UniMidi setup though. Things work reasonably well as long as I sync to an external clock, but I have not been able to implement a 100% stable internal clock with the Ruby Sleep() function. The internal clock works OK most of the time, but sometimes the tempo drops by maybe 10% for 20 seconds or so… probably because some background task kicks in on my MacBook.

I really want to take this project further and eventually I hope to build a complete sequencer for my hardware setup. While playing around with Ruby and UniMidi has been fun, it is clear to me that I will need another platform to reach this goal.

I initially discounted Max/MSP because I really dislike visual programming languages. I spend my days developing software professionally and I like to write code in a text editor. But after doing some more research, I realised that Max actually has a javascript object and that it is possible to create extensions if you want and this has put me at ease.  At least I will have an alternative to huge canvases with a million visual objects and connections.

I’m still not sure if I want to go with live Max for Live or a “pure” Max setup for this project, but I will be doing some research.

Test-Driven Development for Arduino on Windows 7

Arduino UnoWhen I first started programming micro-processors in C, I felt like I had stepped into a time machine that took me back to my early teenage years where I spent long nights learning how to write simple programs on the C64.  But alas, after a few nostalgic programming sessions I found myself falling out of love with of procedures, modules and global variables all over again and started looking for ways to apply some of the things I have learned about software development over the last 30 years or so.

Figuring out how to use basic C++ for embedded development helped me leap about ten years ahead in time to my early twenties, where I started learning about object oriented programming in Java. But I still found micro-controller development to be slow, messy and error prone and I missed the rigour and predictability I have achieved in my programming in recent years by applying TDD. jgade

So I started looking for information on how to write unit tests for micro-controller code and quickly came across James W. Greenings book “Test-Driven Development for Embedded C”, which convinced me I was on to something.

Although the book is choke full of good information, it is pretty sketchy on how to set up a development environment for embedded TDD, as is the documentation for CppUTest — the authors C/C++ unit testing framework of choice. And since I have never done much C/C++ development and have no prior experience with GCC, it took me a while to figure out how to set up a decent development environment on my Windows 7 PC.

I set up the environment for the Arduino because I am working on an project for this board at the moment. However, the unit testing tool chain is completely independent from the Arduino tool chain, so it should be a simple matter to adapt this setup to other boards and micro-controllers.

Step 1: Install Sublime Text with Stino

If you already have a good text editor for Arduino development, you can skip this step. However, if you are still using the standard Arduino editor, I strongly recommend that you give Sublime Text a try.

  1. Download Sublime Text 2 and install
  2. If you have not already done so, grab the Arudino software and install that as well
  3. Open Sublime Text
  4. Click the Preferences > Browse Packages… menu to open an explorer window
  5. Browse up one level and then open the Installed Packages folder
  6. Download Package Control.sublime-package and copy it into the Installed Packages folder
  7. Restart Sublime Text
  8. Click the menu Preferences->Package Control
  9. Type package control install and select Package Control: Install Package
  10. Type arduino and select Arduino-like IDE

You should now see an Arduino menu in Sublime Text.

Step 2: Set up the Example Project

Time to get hold of the arduino-tdd-example project and take your new development environment for a spin:

  1. Open the arduino-tdd-example repository on GitHub and download the zip file
  2. Unzip the project under your  Cygwin home folder (mine is c:\cygwin\home\Rasmus in the windows file system)
  3. Open the helloword.ino file in Sublime Text
  4. Click the menu Arduino > Preferences > Select Arduino Application Folder and select the Arduino folder on your system (e.g. c:\program files\arduino)
  5. Click Arduino > Arduino AVR Boards and select the board you are using
  6. Press Ctrl+Alt+V to compile the sketch

Next, try to upload the sketch to your Arduino:

  1. Connect your Arduino board to your PC
  2. Click the menu Arduino > Serial Port and select the Arduino COM port
  3. Click the menu Arduino > Serial Monitor > Baudrate and select 9600 (this is what the example project uses)
  4. Press Ctrl+Alt+M to start the serial monitor
  5. Press Ctrl+Alt+U to upload the sketch to you Arduino

When the sketch has finished uploading, you should see a Hello world! message in the serial monitor.

Step 3: Install Cygwin and CppUTest

It is possible to use CppUTest with a number of tool chains but the simplest solution is probably to use Cygwin.

  1. Start the latest installer from the Cygwin website
  2. On the packages screen, choose to install all devel packages (they are around 500 MB, so the installation might take a while… some mirrors are faster that others though!)
  3. Once the installation is complete, locate and open your Cygwin home directory in Windows Explorer (e.g c:\cygwin\home\Rasmus)
  4. Download the latest release of CppUTest from the GitHub repository (I used version 3.6)
  5. Unpack the CppUTest folder cpputest-x.y to your Cygwin home directory (the x.y suffix is the version number you are using)
  6. Open the Cygwin terminal
  7. Type cd cpputest-x.y to open the CppUtest folder
  8. Type mkdir build_dir; cd build_dir
  9. Type cmake ..
  10. Type make
  11. Finally, type make check to run the CppUTest tests

All tests should pass.

Step 4: Run the Example Unit Tests

  1. In the cygwin prompt, navigate top the arduino-tdd-example project folder (use /cygdrive/c to access the c: drive in the windows file system)
  2. Type make to run build and run CppUTest

And that all there is to it. Now go write some tests for your Arduino projects!

Hacking a Remote Codec for the Launchpad Mini

42514I decided that I need a better way to select patterns/loops on Reason devices such as Redrum, Matrix and Dr. Octo Rex during live performances.

I know the Livid Ohm64 will do the job and it looks super cool but it’s expensive too. And since I already have a nanoKontrol2 which I’m quite happy with, the Ohm64 seemed like a bit of an overkill.

After a bit of online research I decided on a Novation Launchpad instead and went off to my local music store to get one. I looked at both the full-size “S” model and the “Mini”, both of which I knew to be supported by Reason from my research.

I decided on the Launchpad Mini. I’m OK with the small buttons and I only have so much space on my desktop… plus it’s a bit cheaper than its bigger brother, so what’s not to like?

Well… it turns out that Novation did’t bother implementing their AutoMap software for the Launchpad Mini. And they are not providing any remote codecs for Reason either. So the Launchpad Mini basically just works like a keyboard in Reason… and it’s not even velocity sensitive!

So much for the advertised “Reason support”.

It is  possible to map buttons in Reason to the Launchpad Mini of course, but the buttons on the control surface don’t light up and show the “state” of the software, which was what I expected.


Luckily I applied for access to the Propellerhead Remote SDK a while back and decided to get my hands dirty.

I haven’t actually used the Remote SDK before and it turned out that the most difficult and frustrating part of developing my first remote codec was actually figuring out how to download the SDK! Let’s just say that the Propellerhead developer support could be better…

After I got hold of the SDK things were actually pretty straight forward. It probably took me 7-8 hours to figure everything out and put together the codec. I have absolutely no love for Lua but the Remote API is clean and logical, and the documentation provided in the SDK is pretty good.

I decided to implement most buttons on the Launchpad Mini as simple toggle buttons. Since I plan to map individual Launchpad buttons to different devices in Reason, I decided not to map the buttons to anything by default. I wouldn’t make sense, really.

For the top row of round buttons on the Launchpad Mini (labelled 1-8) I decided to do something special. Rather than acting as toggle buttons, these buttons are mapped to the bar position in Reason: As the song pointer in Reason moves from bar 1 to bar 8, these buttons light up one by one. When the song pointer hits bar 9, the Launchpad “wraps around” and starts from 1 again.

Very cool, if you ask me. I tend to structure the music I make in 8 bar sections and I find that having a visual cue like this during a busy live performance is very useful. This way, I can focus on other aspects of the performance without losing track of the bar count.

The codec can be downloaded from the GitHub. Enjoy!