Posts Tagged ‘launchpad’

Sending MIDI data with the Launchpad Pro

May 10, 2017

Now that we have basic pad handling in place it is time to start doing something musical with the Launchpad Pro.   So I’m going to replicate something akin to the chromatic keys mode of the Launchpad Pro?  No, I’m not going to replicate the whole new scales mode that was released with firmware version 1.4, but we’ll step generally into that direction.

There are two key parts to this:

  • Initial rendering of the display
  • Reacting to the key press and generating the midi event

Rendering the Chromatic Key Display

I’m going to make a few simplifying assumptions for the purpose of this demonstration:

  1. The tonic will be C and nothing else, no changes
  2. No shifting of the octaves – what’s on grid is what you get

So, given those assumptions we can start with pad 11 as C2, which is MIDI note 36 (check out the nice reference at midikits.net and we can initialize our grid data from there using Novation’s partially overlapping row layout.

#define TONIC_R  (32)
#define TONIC_G  (0)
#define TONIC_B  (32)

#define WHITEKEY_R (0)
#define WHITEKEY_G (0)
#define WHITEKEY_B (63)

#define BLACKKEY_R (0)
#define BLACKKEY_G (0)
#define BLACKKEY_B (0)

#define BLACK_R (0)
#define BLACK_G (0)
#define BLACK_B (0)

u8 notegrid[100];
u8 colorgrid[100];
u8 tonic = 36;

void app_init()
{
  u8 note = tonic ;

  for ( u8 i = 0 ; i < 100 ; i++ ) 
  {
    if ( i < 10  || i > 90) 
    {
      // lowest or highest row
      notegrid[i] = -1 ;
      colorgrid[i] = -1 ;
      hal_plot_led( TYPEPAD, i, BLACK_R, BLACK_G, BLACK_B ) ;
    }
    else if ( i % 10 == 0 )
    {
      // left column
      if ( i > 10 )
      {
        note -= 3; // new row so back up the note index a bit
      }
      
      notegrid[i] = -1 ;
      colorgrid[i] = -1 ;
      hal_plot_led( TYPEPAD, i, BLACK_R, BLACK_G, BLACK_B ) ;
    }
    else if ( i % 10 == 9 )
    {
      // right column
      notegrid[i] = -1 ;
      colorgrid[i] = -1 ;
      hal_plot_led( TYPEPAD, i, BLACK_R, BLACK_G, BLACK_B ) ;
    }
    else
    {
      notegrid[i] = note;
      if ( IsNoteTonic(note) )
      {
        colorgrid[i] = 2 ;  //flag for tonic
        hal_plot_led( TYPEPAD, i, TONIC_R, TONIC_G, TONIC_B ) ;
      }
      else if ( IsNoteWhiteKey(note) )
      {
        colorgrid[i]  =1 ; // flag for white key
        hal_plot_led( TYPEPAD, i, WHITEKEY_R, WHITEKEY_G, WHITEKEY_B ) ;
      }
      else
      {
        colorgrid[i] = 0 ; // flag for black key
        hal_plot_led( TYPEPAD, i, BLACKKEY_R, BLACKKEY_G, BLACKKEY_B ) ;
      }

      note++ ;
    }
  }
}

This code will initialize arrays of note and color data as well as set the initial pad colors.  The colors should looks something similar to the normal Novation chromatic scale mode.

Determining the colors of the musical pads comes down to a couple of functions that rely on midi data arrangements:

u8 IsNoteTonic( u8 note )
{
  // any multiple of tonic + 12 will mod to 0
  return (( (note-tonic) % 12) == 0) ;  
}

u8 IsNoteWhiteKey( u8 note )
{
  if ( (note %12) == 0 ) return 1; //C
  if ( ((note-2)%12) == 0) return 1; //D
  if ( ((note-4)%12) == 0) return 1; //E
  if ( ((note-5)%12) == 0) return 1; //F
  if ( ((note-7)%12) == 0) return 1; //G
  if ( ((note-9)%12) == 0) return 1; //A
  if ( ((note-11)%12) == 0) return 1; //B
  return 0 ;
}

u8 IsNoteBlackKey(u8 note)
{
  if ( ((note-1) %12) == 0) return 1; //C#
  if ( ((note-3) %12) == 0) return 1; //D#
  if ( ((note-6) %12) == 0) return 1; //F#
  if ( ((note-8) %12) == 0) return 1; //G#
  if ( ((note-10) %12) == 0) return 1; //A#
  return 0;
}

N.B. we could flip the white/black key assignment logic in app_init by using the IsNoteBlackKey function and save a couple of CPU cycles since the IsNoteBlackKey function is two if-statements shorter in the worst case.

Sending MIDI

The hal_send_midi function is what we are really interested in today.  It takes 4 parameters, the first of which is the port to send the MIDI data out on.  We can choose DINMIDI for the traditional 5 pin DIN MIDI connector, or USBMIDI to send out the USB connection (to be received by something like Ableton).  There is also USBSTANDALONE, but unfortunately I have been unable to locate any documentation about that setting.

The last three parameters are the heart of MIDI data.  Many MIDI messages amount to sending three bytes of data: a MIDISTATUS byte and two data bytes.  For this post I’m only interested in sending NOTE ON and OFF messages.  The MIDI status byte is divided into two nibbles where the high nibble indicates the type of message (NOTE ON, NOTE OFF, PROGRAM CHANGE, CONTROL CHANGE, etc.) and the low nibble indicates the MIDI channel.   If we set up constants for NOTE ON and OFF with the data in the high nibble (i.e. 0x90 for on and 0x80 for off), we can bit-wise OR the channel number into the low lower nibble.  For example:

u8 midistatus = 0x90 | 0x01 ;  // MIDI NOTE ON for channel 2

The remaining two data bytes are specific to each type of message.  In our case, NOTE ON/OFF requires the note to play (we can use the notegrid array for that value) and the velocity of the pad press.

The app_surface_event method is interesting in that while it provides a velocity value (the third parameter “value”), it really only allows for key press velocity, not key off velocity.  It uses a value of 0 to indicate key off and 1-127 as the key on velocity.  So, in our case we can use the value parameter to tell us to send a MIDI NOTE ON or OFF, and use it to send the MIDI NOTE ON velocity value.  For NOTE OFF we will have to make something up…

Putting it all together

Let’s put that to use in the app_surface_event function:

#define MIDI_STATUS_NOTE_OFF (0x80)
#define MIDI_STATUS_NOTE_ON (0x90)

// actual midi channel is 6
// as that's where my http://www.audiothingies.com/product/micromonsta/ is...
u8 midiChannel = 5; 

void app_surface_event(u8 type, u8 index, u8 value)
{
  if ( type == TYPEPAD )
  {
    if ( index < 10 || index > 90 )
    {
      // top or bottom rows
    }
    else if ( (index % 10 == 0) || (index % 10 == 9) )
    {
      // left or right columns
    }
    else
    {
      // ONLY CARE ABOUT THE CENTER 64 PADS
      u8 lightUpLowerRow = (index % 10 < 4) && (index > 20);
      u8 lightUpUpperRow = (index % 10 > 5) && (index < 80);

      // VALUE == 0 INDICATES PAD BEING RELEASED
      if ( value == 0 )
      {
        if ( colorgrid[index] == 2 )
        {
          hal_plot_led( TYPEPAD, index, TONIC_R, TONIC_G, TONIC_B ) ;

          if ( lightUpLowerRow )
          {
            // light up the pad on the lower row
            hal_plot_led( TYPEPAD, index-5, TONIC_R, TONIC_G, TONIC_B ) ;
          }
          else if ( lightUpUpperRow )
          {
            // light up the pad on the upper row
            hal_plot_led( TYPEPAD, index+5, TONIC_R, TONIC_G, TONIC_B ) ;
          }
        }
        else if ( colorgrid[index] == 1 )
        {
          hal_plot_led( TYPEPAD, index, WHITEKEY_R, WHITEKEY_G, WHITEKEY_B ) ;

          if ( lightUpLowerRow )
          {
            hal_plot_led( TYPEPAD, index-5, WHITEKEY_R, WHITEKEY_G, WHITEKEY_B ) ;
          }
          else if ( lightUpUpperRow )
          {
            hal_plot_led( TYPEPAD, index+5, WHITEKEY_R, WHITEKEY_G, WHITEKEY_B ) ;
          }
        }
        else
        {
          hal_plot_led( TYPEPAD, index, BLACKKEY_R, BLACKKEY_G, BLACKKEY_B ) ;

          if ( lightUpLowerRow )
          {
            hal_plot_led( TYPEPAD, index-5, BLACKKEY_R, BLACKKEY_G, BLACKKEY_B ) ;
          }
          else if ( lightUpUpperRow )
          {
            hal_plot_led( TYPEPAD, index+5, BLACKKEY_R, BLACKKEY_G, BLACKKEY_B ) ;
          }
        }
        // SEND MIDI NOTE OFF with high velocity since we don't know what it was
        hal_send_midi( DINMIDI, MIDI_STATUS_NOTE_OFF | midiChannel, notegrid[index], 127) ;
      }
      else
      {
        hal_plot_led( TYPEPAD, index, KEYPRESS_R, KEYPRESS_G, KEYPRESS_B ) ;

        if ( lightUpLowerRow )
        {
          // light up the pad on the lower row
          hal_plot_led( TYPEPAD, index-5, KEYPRESS_R, KEYPRESS_G, KEYPRESS_B ) ;
        }
        else if ( lightUpUpperRow )
        {
          // light up the pad on the upper row
          hal_plot_led( TYPEPAD, index+5, KEYPRESS_R, KEYPRESS_G, KEYPRESS_B ) ;
        }
        
        //SEND MIDI NOTE ON with provided value as velocity
        hal_send_midi( DINMIDI, MIDI_STATUS_NOTE_ON | midiChannel, notegrid[index], value) ;
      }
    }
  }
}

I don’t love all that duplication of if-statements but there’s really only one real alternative algorithm and it leads to less readable code for no significant benefit.

Wrapping up

Throw that all in an app.c, compile it (with the missing callbacks) and load it into your Launchpad Pro.  You will end up with an overlapping chromatic grid similar to the normal one that emits to MIDI channel 6.

Steps beyond this would be:

  • Support moving through the octaves
  • Hook the SETUP button to allow the user to:
    • pick a MIDI channel
    • pick a scale
    • Pick a key

Handling Pad Events on the Launchpad Pro

March 19, 2017

Building from the basic understanding of how to affect the Launchpad Pro pads, the next thing we will be interested in doing is taking an action when a pad is pressed.

The API defines a number of callbacks that we can hook into to do interesting things. The one we’re interested in today is:

void app_surface_event(u8 type, u8 index, u8 value);

Like the hal_plot_led API call, the type parameter is either TYPEPAD or TYPESETUP allowing us to know when the setup button is pressed as opposed to a normal pad. Similarly, the index parameter tells us which pad is pressed (and can be ignored when the type parameter is TYPESETUP).

The last parameter, value, is different. When a pad is initially pressed, the app_surface_event callback is invoked with a value 1-127. When the button is released, the app_surface_event is invoked with a value of 0. You can see this in action with this bit of code:

void app_surface_event(u8 type, u8 index, u8 value)
{
    hal_plot_led( TYPEPAD, index, value/2, value/2, value/2) ;
}

It will initially alter the pressed button to be some intensity of white depending on how hard the button was pressed. When the button is released a second event with a value of 0 will be received and the pad will turn off.

It is important to note that without the code above pressing a button has no effect. However, that means we can make it do anything we want it to do… such as sending MIDI data…

Setting the Colors on the Launchpad Pro’s Pads

March 18, 2017

Now that I have figured out how to re-program the firmware on the Launchpad Pro it is time to do something useful with it. There’s multiple parts to what I have in mind but today I experimented with coloring the pads.

There is a nice API for setting the color of a pad. From the app.h include file we find:

void hal_plot_led(u8 type, u8 index, u8 red, u8 green, u8 blue);

The first parameter, type, has two possible values: TYPEPAD and TYPESETUP. TYPEPAD is used to address the round and square pads on the Launchpad Pro. TYPESETUP is used for the recessed setup button in the upper left corner of the device. When using TYPESETUP, the second parameter (index) is ignored and the color of the vertical LED on the bottom edge of the device is altered.

The second parameter, index, is used to address the pads on the device. Check out the Novation documentation for a nice picture of the pad indexing but the summary is this: values 0 to 99 starting from the bottom left corner, moving left to right and moving up. So the “Record Arm” button is index 1, while the “User” button is index 98. Indexes 0, 9, 90 and 99 are not mapped to anything. One might think that index 90 would address the Setup button, but it does not.

The last three parameters are fairly obvious: the red, green and blue values required to render a color. Note that RGB values are often expressed as values 0-255. The Launchpad Pro uses 0-63. Therefore, if you use a site like http://htmlcolorcodes.com/color-names/ to find colors you will need to divide the individual values by 4 for similar colors on the Launchpad Pro. RGB(0,0,0) normally corresponds with black. But for our Launchpad, it turns the pad off.

With the API well in hand I’m going to need to create visual differences between a button that’s active and a button that’s available but not active, and a button that’s off or unavailable. Certainly, RGB(0,0,0) will suffice for off/unavailable but how should we represent available but not active? Working with good strong colors like RGB(63,0,0) and RGB(32,0,32) I experimentally determined that dividing each value by 4 or 8 yields a clear enough difference between the full color (active) and reduced color (available) but still allows for a color that properly represents the full/active color.  So, for a nice purple with active/full as RGB(32,0,32) we can use RGB(8,0,8) for the inactive/available situations.

Instructions for Launchpad Pro Firmware Development

March 11, 2017

A bit ago while I was answering a question in the Facebook Circuit Owners group I mentioned that I’d not been able to figure out how to program my Launchpad Pro. It didn’t sit well with me after I wrote that statement. I’ve been a software developer for a long time and embedded systems is my original area of specialty.  What could possibly be that hard about it? So, I went back for a second (actually third) look at what it took…

The original release of the Launchpad Pro celebrated the open platform that Novation was providing as part of the product release. The primary documentation for working with that platform is at https://github.com/dvhdr/launchpad-pro. Turns out, while there’s a fair bit of documentation there, the reality is it is just barely enough documentation to get it done, and it is not quite right (at least not on the master branch). I’ve determined there’s a couple of other branches, one of which has the major corrections in it that I make below, but none with fully detailed instructions.

The end result was that I was able to get some firmware into my Launchpad Pro.  But, it wasn’t perfectly straightforward.  So, I’ve decided to provide some updated and more detailed instructions.  I do presume some reasonable knowledge of software development but hopefully this helps the Novation Launchpad Pro community.

Prerequisites

These instructions are MS Windows biased, but I think they should translate to MacOS easily enough.

You will need the following tools installed and ready to go:

  • A git client
    • git will need to be in your command line path
  • An ssh client (e.g.: part of MinGW)
    • ssh will need to be in your command line path
  • Vagrant
  • VirtualBox
  • A MIDI tool that can send sys-ex (e.g. MIDI-OX)

My personal laptop has Win10 and 8G of RAM on it and for me it is just barely sufficient. I really can’t run much other than the VirtualBox and MIDI-OX at the same time.

First Steps

  • Find or create a folder to work in
  • Open a command prompt in that work folder
  • Execute:
git clone --recursive https://github.com/dvhdr/launchpad-pro.git
  • This creates a launchpad-pro folder in the that work folder

You now have the basic Launchpad Pro files on your computer.

However, the Ubuntu image that is going to be used in this setup has changed since the code was uploaded to github. Therefore, we need to make a small change to one of the files downloaded.

  • Move to the launchpad-pro folder and open the Vagrantfile in a text editor
  • Find the line that starts with ‘config.vm.box’
  • Change it as follows, Before:
config.vm.box = "drmyersii/ubuntu-desktop-14.04-x64"
  • After
config.vm.box = "drm2/ubuntu-14.04-desktop-x64"

Novation support graciously point me at the new location when I asked about why there was a problem originally (and this nicely agrees with the last change on the raw-ADC branch that I found after I asked…).

VM Setup

  • Using your command prompt, move into the launchpad-pro folder
  • Execute:
 vagrant up

Let vagrant complete its work before moving on or logging into the VM.

  • Log you into the Ubuntu VirtualBox instance, execute:
 vagrant ssh
  • Execute:
make

The make is going to run for a good bit of time but we can do a couple of things while it is doing its thing.

Ubuntu/Eclipse Setup

The new Ubuntu image that we are using does not include an Eclipse installation (despite what the original docs say). But, it is not hard to set up.

  • Switch over to the VirtualBox instance and log into VirtualBox
    • It should already be running at this point with the vagrant user prompting for the password – just use “vagrant” as it the password
    • You may get prompted to update. I didn’t, but it is something that should be done soon to ensure all of the security patches are installed if you’re going to use this for anything beyond Launchpad Pro development
  • On the left sidebar there is an icon that looks something like an orange portfolio with an A on it. It is the Ubuntu Software Center. Launch it.
  • In the upper right of the Software Center, there’s a search field. Type in “eclipse” and look for “Eclipse Integrated Development Environment”.
  • Click on that row and there should be an “install” button. Install it.
    • This will take a little bit of time.
    • At the end of the install you will be prompted to authenticate the installation – just use vagrant password again.
    • The install button eventually change to “remove” (don’t remove it)
    • Note that there is now a new Eclipse icon in the left sidebar.
  • Launch Eclipse
    • If prompted for a workspace, accept the default and check the box to make it the default.

Once Eclipse shows you the main window we need to do a bit of configuration in Eclipse

  • Go to the Help/Install New Software… menu
    • I’m not sure what GUI Ubuntu is using these days but they hide the standard toolbar in the top status bar. Simply move your mouse up to the top bar next to the “Eclipse” text and the menu will reveal itself. Yes, I agree, really questionable UX…
  • Using the combobox to the immediate left of the “Add…” button, pick “Indigo Update Site”
  • Scroll down the list to the Programming Languages area and expand the list.
  • Select the “C/C++ Development Tools”
  • Leave the defaults alone from here out and click Next as many times as necessary until you can click Finish, which you also click.
    • You may get prompted to acknowledge licensing agreements and what not… do what you need to do.
  • When it is finished you will be prompted to restart Eclipse. Don’t. Instead, shut Eclipse down completely
    • This is just for the ease of the next step. Normally the restart is just fine.

We need to go back to our ssh session and check on the progress of our make command. When it is done we can switch back to the VirtualBox.

Pulling in the Source Tree

We now have a development environment for building our Launchpad Pro firmware but we need to pull the source code into Eclipse.

  • Launch Eclipse
  • File, Import…
  • Find C/C++ in the list and expand it.
  • Click on “Existing code as Makefile project” and then click “Next”.

It turns out that the launchpad-pro folder in your main computer’s work  folder is mapped into the VirtualBox’s /vagrant folder.

  • Put “/vagrant” in the “Existing code location” text field
  • Set the project name to whatever you want (it defaults to “vagrant” which is probably fine in some situations but isn’t for ours IMO)
  • Leave the other things alone and click “Finish”
    • If you have not closed the “Welcome” tab, go ahead and do so.

Building the Default Code

We now have a project in the upper left of Eclipse with the name we provided in the previous dialog. Time to build this thing:

  • Right click on the project and select “Clean Project”
  • Right click on the project and select “Build Project”

There is now a launchpad_pro.syx file in the launchpad-pro/build folder.

Upload to the Launchpad Pro

Finally, we have a binary image to upload into the Launchpad Pro. Ensure your Launchpad is plugged into your computer (and in bootloader mode) and using your SysEx tool of choice (I use MIDI-OX) to upload it (from <your-work-folder>\launchpad-pro\build\launchpad_pro.syx) and restart the Launchpad Pro.

You might have to hit the setup button to start the new firmware but it is there and running.

Useful References