Hacking an M-Audio O2 controller

Miscellaneous
1

Back again after getting a job and such. :wink:

I’ve got a question about utilizing an existing MIDI controller and modifying it to be more useful. I took apart my old M-Audio O2 25-key controller last night, and I’m having ideas about what to do with it. I already have a full-size MIDI keyboard, so what I’d like to do is hack the 25 keyboard key buttons and replace them with either pots or push buttons (pots if possible). I’m also hoping I could do the same thing with a 49-key Yamaha keyboard with MIDI-output.

Any ideas on if this is possible, or is the signal only on-off and dedicated as a certain note when it comes to the keys?

2

You want to replace keys with pots? Explain, this sounds weird.

3

.. so what I’d like to do is hack the 25 keyboard key buttons and replace them with either pots or push buttons (pots if possible). I’m also hoping I could do the same thing with a 49-key Yamaha keyboard with MIDI-output.

Hey there.

In short, you won’t be able to replace the key contacts (inside your controller) with Pots.. well, you could, but it won’t be turnt into some magical controller..

Each key on your keyboard has two switches inside.. when you press a key, one switch, then quickly after that, the other switch make contact… the timing between them is converted into the velocity of the note.. (Makes sense? shorter timing = you smacked the key hard)

You would be able to hack apart the controller and make a box with 25 buttons on it.. and it would easily be configurable with something like ableton to launch audio clips etc.. but then again, if you went to all that trouble, you might as well build a proper controller for ableton etc with rotary encoders and flashing leds etc..

For ideas what to do with a MIDI controller… look at what I did with my 4 octave controller.. I turned it into a synth (Still work in progress)

http://www.midibox.org/forum/index.php/topic,12413.90.html

Kind Regards

Mike

4

It doesn t really make any sense to use a working MIDI keyboard keys to be retrofitted with a new controller…

5

It doesn t really make any sense to use a working MIDI keyboard keys to be retrofitted with a new controller…

I’ll try to clarify: Since I already HAVE a full-size MIDI keyboard, I want to convert my little O2 into a controller with more buttons or pots than it already has (8 of each, plus the octave and mod levers, which are kinda lame but may be useful as rotary encoder inputs). In other words, if I can take a controller with 8 pots and a bunch of keys I don’t need to use, and transform it into a controller with 8 or MORE pots and 25 BUTTONS, or some combination thereof, it would be more useful to me. I also want to do it with the parts I have and without programming. If I had money to spend at the MIDI store, I would do that, but this is a project for fun, just to see what I can do. Isn’t that how this whole community started?

Mike, thanks for the info. I noticed the two switches, that makes sense about the key velocity. I guess that means I can’t use each of those contacts for a separate button, right? (Or possibly for velocity pads for percussion. . . .)

About the pots: I see that the key contacts are actually two parts each, separated by a small space, so the key must close that circuit when it presses down and bridges that space. My thought was that I could bridge that space with a pot instead, but then I came to the main question of all this which was whether the signal would even go through correctly (since a note is just on/off, whereas the pot sends a variable voltage, and notes don’t really have any variance included besides the velocity, which is taken care of by the dual-switch thing). Is my thinking correct so far?

Thanks for the replies!

6

First of all: It is soo(oo)x (x->?) much more easy to simply build your midibox from scratch with the common midibox modules.

You could sell your O2 on ebay and spend the money on your midibox.

About the pots: I see that the key contacts are actually two parts each, separated by a small space, so the key must close that circuit when it presses down and bridges that space. My thought was that I could bridge that space with a pot instead,

that is completely wrong.

hint: http://en.wikipedia.org/wiki/Potentiometer

but then I came to the main question of all this which was whether the signal would even go through correctly (since a note is just on/off, whereas the pot sends a variable voltage, and notes don’t really have any variance included besides the velocity, which is taken care of by the dual-switch thing). Is my thinking correct so far?

I hope you understand the Digital/Analog difference.

As for the buttons, the microprocessor in the O2 expects either a “1” or a “0” and nothing in between.

There is *no* chance to add additional analog inputs to the O2 for pots, faders, etc. without completely hacking the microprocessor and the program code and all that stuff.

Do yourself a favour and build yourself a MB  :wink:

7

Quote

It doesn t really make any sense to use a working MIDI keyboard keys to be retrofitted with a new controller…

Without any rationale behind your reply, that doesn’t add much to the conversation.

Thanks, it probably doesn t add that much to you or to the conversation but for sure it takes my own time which i could spend somewhere else so please next time try something like

“hey Simone you short answer doesn t really make sense to me please try to clarify your point”

Now i see i ve misunderstood what you are trying to do, it was not clear in your first post, about the keys: you want to replace every key with a pushbutton, right? So basically this is not a MIDIBox project so this post should be in Miscellaneous

In other words, if I can take a controller with 8 pots and a bunch of keys I don’t need to use, and transform it into a controller with 8 or MORE pots and 25 BUTTONS, or some combination thereof, it would be more useful to me. I also want to do it with the parts I have and without programming

Analog inputs can be used as digital inputs but not the other way round

I noticed the two switches, that makes sense about the key velocity. I guess that means I can’t use each of those contacts for a separate button, right? (Or possibly for velocity pads for percussion. . . .)

no you can t use them separately and no you can t use them for drums, the double switch system needs a real mechanical movement of the key while drum triggers and pads usually use piezos to detect the vibration of the strike

That said you could try to create some custom pad that would reuse the key mechanism somehow..

There is also some code that calculates the time a button is pressed and transform it in velocity dig in the downloads

About the pots: I see that the key contacts are actually two parts each, separated by a small space, so the key must close that circuit when it presses down and bridges that space. My thought was that I could bridge that space with a pot instead, but then I came to the main question of all this which was whether the signal would even go through correctly (since a note is just on/off, whereas the pot sends a variable voltage, and notes don’t really have any variance included besides the velocity, which is taken care of by the dual-switch thing). Is my thinking correct so far?

correct, i would advise you to get a clearer idea of digital and analog input as well as MIDI note on/off and cc, that would help you a lot in this hack

Simone

oops and yes i would definitely follow SLP advise

8

Simone:

I’m sorry. Thank you for all the info in your last post. Yes, this probably should be in a different forum, now that you mention it. Yes, it would probably be better to build a MIDIBox using documented methods. This all started because I got curious last night, and wanted to play with it today. Ordering parts takes time and money, this was supposed to be an alternative. In fact, it was really just a learning project, and I was looking for direction.

I guess I’ll just have to build a MIDIBox by the book. Of course, that’s what I said a year ago.

9

@ Simone and SLP:

I must admit, I completely spaced the whole digital/analog thing when I was thinking about this. I’ve spent hours reading about all of that in the past, I have no idea why my brain was so out of it. I’m mostly trying to defend my intelligence, for what that’s worth at this point. :wink:

But I do understand how buttons and rotary encoders differ from analog pots. I guess my head was somewhere else the other night. Anyway, thanks again for the input.

10

Don’t worry, it happens to us all. There’s even a word for it: *brainfart*

11

I guess my head was somewhere else the other night. Anyway, thanks again for the input.

Ladies?.. It’s usually the ladies…

12

Ladies?.. It’s usually the ladies…

Could be - I’m always keeping one eye on my 18-month-old daughter. :slight_smile: