Comments on: Arduino MIDI Volume Pedal

By: GDLive

GDLive — Mon, 29 Nov 2010 10:11:02 +0000

Hi, nice work !

I’m trying your example since I’m not able to reproduce simplest arduino-midi out wiring (such as here :
http://itp.nyu.edu/physcomp/Labs/MIDIOutput
).Doesn’t work for me, as I said here :
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1290794831

Since I’ve haven’t PNP transistor nor 7404 Hex inverter (i’m note sure to understand what it is for), I tried your second proposal with two NPN 2PN2222.

“>Finally, I’m not sure why I used the wacky PNP-NPN buffer circuit instead of two NPNs with a 10K from TX to Q1’s base, emitter tied to ground, 10K from VCC to Q1’s collector and Q2’s base (acting as a pull-up), and the remainder of Q2 and the DIN connector’s configuration the same.<"

Result : I don't see any midi message on my soundcard !

I don't know what I could try, every suggestion would be welcome !

Thanks

By: Misha

Misha — Fri, 26 Nov 2010 16:51:09 +0000

Can you make this work with 4 pedals, and can you run MIDI through thins unit? I have an organ project, and if it is possible, it could save hundreds of dollars!

By: Giovanni

Giovanni — Sat, 14 Aug 2010 19:10:09 +0000

Thank you for the example.
But above I read :”So the code reads the potentiometer position in the range 0-4095; divides it to get it to the range 0-127; and sends:…”

Only a little comment
The Arduino A/D converters are 10 bit wide so the values obtained are in range of 0-1023. And thus it is right to divide by 8 to obtain a number among 0-127

By: Andy

Andy — Tue, 19 Jan 2010 19:30:31 +0000

Marco,
If you want something pre-built, I don’t know of anything built into a pedal, but MIDI Solutions makes the footswitch controller, which can take a footswitch input and spit out whatever MIDI Message you require. They also make the Pedal Controller, which accepts an expression pedal and can convert that to any desired message (aftertouch, pitch bend, cc, or sysex). So it’s basically a closed-source version of the same concept as Keith’s pedal, if you’re just looking for something ready-to-use. http://midisolutions.com

–Andy, a MIDI Solutions customer, and somewhat of a friendly-competitor

By: Marco

Marco — Tue, 19 Jan 2010 12:17:26 +0000

Alo Keith,
Nice work, congratulations for sharing this information.
I´trying to find a single midi controller pedal, do you know something like this…?
like a single control pedal for keyboard but as a midi controller.

If you know something please let me know…

Thanks and kind regards
Marco Santos

By: Keith Neufeld

Keith Neufeld — Fri, 26 Jun 2009 12:46:23 +0000

Elvio, actually, see my conversation in the comments with Drew. There are pedals that change the resistance between tip and ring on a TR 1/4″ plug, and there are pedals that change the voltage on one of the pins (I forget which) on a tip-ring-sleeve (TRS) 1/4″ plug. The two aren’t compatible, and this particular circuit uses the latter.

I can’t guarantee which of the two methods an audio volume pedal and a MIDI expression pedal use — in fact, I can’t even guarantee it’ll be the same for all audio volume pedals or all MIDI expression pedals. (It may be, but I’m not familiar enough with those markets.) But all pedals with TR plugs should be compatible with each other, and all pedals with TRS plugs should be compatible with each other (with the exception that some might work backwards, and some might have a switch to correct for working backwards).

The Arduino is developed and manufactured in Italy, so I know you can get it in Europe (although I don’t know where). A 1/4″ TRS jack, the 5-pin DIN connectors, and the resistors and transistors for the MIDI interface should also be available at any electronics parts store.

Can any of my European readers tell me, do you have electronics stores like Radio Shack that are everywhere but have only the barest essential components for hobbyists, and stores like Frye’s that are sparse but have everything? Also do you have preferred mail-order sources different than Digi-Key and Mouser that have better shipping costs to Europe?

By: Elvio

Elvio — Fri, 26 Jun 2009 06:21:51 +0000

Thanks so much, Keith!
…seems crazy to me: do you mean that an audio volume pedal and a MIDI expression pedal have the same output???
Could I possibly connect an audio pedal to a controller and have the same results?

As for the circuit… I found two commercial solutions, both quite expensive:
http://www.thomann.de/fr/midi_solutions_pedal_to_midi_converter.htm (117€, one input, one 5pin output)
http://www.eowave.com/controllers.php (120€, four inputs, one USB output) (for some reason the site is down at the moment)
…so well, I’d like totry the DIY way! Do you know if the parts are available in Europe?

€:-I

By: Keith Neufeld

Keith Neufeld — Thu, 25 Jun 2009 22:44:03 +0000

Elvio, what I built is exactly what you need, for exactly the reason that what you tried didn’t work.

The problem is that MIDI (“Musical Instrument Digital Interface”) is a digital signal and expression pedals are analog resistance. Even expression pedals sold for “MIDI controllers” are analog inputs to a controller that’s doing what my little circuit does. Connecting the analog signal across pins in the MIDI doesn’t do anything useful.

The circuit I wired is basically a tiny MIDI controller built custom just to run an expression pedal. It’s the same as if you bought a MIDI controller (or control surface) and plugged the pedal into it and it into the Motu. The only difference is (perhaps) size — you can see how small this circuit is. It could be made even smaller if it were purpose-built instead of on a general-purpose prototyping board.

So … I’m not sure what to suggest. I could certainly build you this circuit into a box the size of a guitar pedal and you’d have a smaller thing to take with you, but I don’t know if that’s what you want. Plus it’d cost somewhere around $35-50 in parts (including the case), and I don’t know how that compares with what you’d pay for other solutions.

By: Elvio

Elvio — Thu, 25 Jun 2009 21:19:46 +0000

Dear Keith,
When I saw the picture on this page, I thought: “That’s it!”… but it was not quite, actually…
I recently bought a Motu Ultralite MK3 interface. I would like to connect my guitar and a mic. As I would like to control the volume of the guitar with a pedal, I tried an Ernie Ball volume pedal… but I didn’t like it at all :
1) the tone really gets worse
2) and the range of the pedal is closer to a switch!
So, I am trying another approach. I have a MIDI expression pedal. Connecting it to my Mac, with a simple Max/MSP patch I can simply lower the volume of the channel, with no tone loss, and with a scale that I decide. So, bingo?
Well, not yet… The only way I can connect this pedal (an MGear Ex-P, by the way) is through a keyboard or a control surface that has the appropriate stereo-jack entry… and I wouldn’t have to transport this equipement just for this purpose.
So, I ask you: is it possible to connect an expression pedal to the 5-poles DIN standard MIDI IN of the MOTU interface ?
I am a musician, and all I can do with electronics is soldering some audio cables, but I did my best to understand the MIDI process.
If I got it well, a 5v tension runs to and from pins 4 and 5; the pedal is just a potentiometer, a variable resistance that reduces this tension…
I wired it all, but it does not work. Why?
Thanks in advance,

Elvio

By: Andy

Andy — Thu, 30 Apr 2009 01:03:47 +0000

My bad, I should have clarified I meant Tom’s simplified circuit, without the inverter/transistors.

My concern is that a problem might arise if Vcc is higher than the 3V3 the processor is running at (most likely itd be the standard MIDI 5V), thered be a potential voltage difference of up to 1.7V between the serial out and Vcc. If it were an open-collector, no prob, I’m not sure about the Arduino’s, though.

(And there’s the further chance that it might hit another “utility extension” device (like a MIDI Solutions Relay) that isn’t opto-isolated, so…)

Thanks,
Andy