Tell us about your experience with Open.Theremin

I stand corrected by dewster. The filtering is "clocked" by the pitch timer interrupt (and not by the HW interrupt as I wrongly remembered) so that the F3 of the LPF (and thus the latency) will depend on the actual heterodyning frequency.

Thanks for that clarification Thierry!  I don't want to impose on you, but if some point you have a scope on your UNO, could you perhaps confirm / deny the frequency at TP8 is the same (or nearly the same) as the audio frequency when doing the HW pitch calibration?  If so, that would really nail down the analysis.

Thierry, I'm wondering if you can detect latency in the UNO by placing your hand near the pitch antenna and waving it slowly side to side, and compare this to waving your hand quickly side to side?  (On the Theremini it is obvious that quick movements don't produce as much pitch change as slow movements.)

I have a deep debt to Urs for sharing his techniques / secrets within the UNO, they are basic yet profound (the best kind).

"If that is the case then filtering happens at a much lower rate than...  ILYA, could you comment on this?" -- dewster

yea, you're right.
Fc in your formula must be the routine rate (aka capture event rate, aka "actual heterodyning frequency"), i.e. around 600Hz.

The Open Theremin is hacked, the Theremini is half hacked, what will be next?
Вonsoir Thierry... How about your experience with tVox? (with photos of internals please;) )

"Вonsoir Thierry... How about your experience with tVox? (with photos of internals please;) )" - Ilya

Oh, we all long for that!

I have a feeling that hell will freeze over first..

See Technical Hijack thread for some Tvox photos from this site..

http://www.mb-labo.com/Theremin/t-Vox.htm

Fred.

"Вonsoir Thierry... How about your experience with tVox? (with photos of internals please;) )" - Ilya

Oh, we all long for that!

I have a feeling that hell will freeze over first.. (Fred)

LO........OL!

I think you might be right there Fred, and in some ways, yeh, why not since if we knew everything about everything then what would there be to look froward to!

Anyhew, aboot yon theremin engineers V's the thereminists, well, as far as I'm concerned there should be room enough for both. Antonio rapped with the fiddlers so why should things be different in today's electronic age?

(Yon engineers at MOOG take note pleeeeze!)

"Fc in your formula must be the routine rate (aka capture event rate, aka "actual heterodyning frequency"), i.e. around 600Hz."  - ILYA

Thanks!  Do you notice any latency on the pitch side?  I've read that an absolute (brick wall MIDI) latency of > ~10ms starts to make keyboardists feel that something is rather disconnected, but I have no idea where first-order LPF F3 should be on a digital Theremin for comfort (though I suspect 27Hz far field is too low).

I bought an open.theremin with the intention of converting it into a MIDI controller. The simplest approach is one I have already tried with another theremin which works very well: send only pitch bend and volume messages and do everything else (i.e. note generation) with MIDI afterwards. I've connected a MIDI output to digital pin 1 of the Arduino, which is working, even with the theremin attached. What I would like to do is modify the standard code for the open.theremin. Ideally it should still output the calibration beeps, but not generate audio from the look-up table, instead sending something to digital pin 1 (in MIDI format, or just numbers representing input from the antennas in some intelligible format; I'm sure I could progress from there).

I don't know anything about programming, and my attempts to do anything like this so far result in a mess of compiling errors. I'm still not sure the device will be sensitive enough, and I don't want to spend six months learning how to program an Arduino to this level before finding out that it isn't. (or is, hopefully!) Anyone have any thoughts about this? 

I've been scouring these forums for anything that could help me.  Here is a quote from Dewster, Posted: 11/27/2012 4:11:41 AM.

"A digital Theremin could generate MIDI data almost trivially."  I would love to find out how, with relation to the open.theremin.  My own attempts to achieve this have not been very successful, despite the fact that it seems as though it should be relatively easy.

"I don't know anything about programming, and my attempts to do anything like this so far result in a mess of compiling errors. I'm still not sure the device will be sensitive enough, and I don't want to spend six months learning how to program an Arduino to this level before finding out that it isn't. (or is, hopefully!) Anyone have any thoughts about this?" - chrisransome

Not exactly sure what to tell you as I'm not familiar with the compile environment for the Arduino, though I have inspected the Open.Theremin code somewhat and it seems fairly straightforward for what it does.  The Arduino is so overpriced and under-powered it doesn't interest me much.  But it likely has enough horsepower to kick out MIDI, particularly if it isn't bogged down generating audio.  I haven't played with an actual Open.Theremin to know the useful size of the pitch field (I assume this is what you mean by "sensitive enough") but what is there is very likely more linear near the antenna than other offerings.  You might ask around on Arduino sites about the compile / coding errors you're getting.