Muff's Modules & More

reve

Hey wiggle-pals! Two parter here:

1. Anyone wanna help with this project?
2. Assuming it gets put together correctly, any interest in boards?

So I'm working on this Arduino-based Polyphonic ADSR, but I got sidetracked with a slightly easier project -- an Octature LFO. That is to say, eight outputs 45 degrees out of phase. Alternatively, you can flip a switch and enter "polyphasic mode." In this mode, instead of each output being 45 degrees out of phase the amount of phase shift is controlled with a pot or with a voltage source of your choosing.

For example, the 180-degree shifted output is 0 degrees out of phase at knob position 0, 180 degrees out of phase at 12 o'clock, and 360 degrees out of phase at position 10. All the other outputs would be similarly shifted... at position 0 the 45 degree output would be in phase, and at position 10 it'd be like 90 degrees out of phase. Hook that sucker up to a wogglebug and neat stuff happens.

Since the frequency control is just an ADC in, that's also voltage controllable.

The project is in "functional pre-beta" now. If you have an Arduino and a Maxim 528/529 DAC on hand you'd be able to build a working module (since those outputs are buffered). There's a few things I'd like to address:

1. I'd like to move to a 10 bit dac (LTC1660) and a 10 bit sine sample. This will push the overall speed of the oscillator down and decrease aliasing. I stepped up to a 32 bit phase accumulator already. Kinda silly at this point with a 32 bit accumulator and an 8 bit sine table, but that's the rationale.

2. I get aliasing on the outs now with fast frequency changes. This could probably be solved with simple RC filters on the outputs; the outputs will all need to get buffers and their levels fixed anyway. So broadly speaking, "the analog section needs to be designed."

3. I'm obviously not a programmer, so... anything anyone sees that should be done better. Please lemme know. Or better still, I'll get you write access to the repo.

Anyway, if you're interested please take a look at the code:
https://github.com/rmosquito/PolyLmFaO

Parts involved if this went into board / kit land would all be through-hole & DIP packages. One AVR ($2), a crystal, one octal DAC ($5), a couple quad op amps and some passive components.

Interest? Suggestions? Thanks!

raisinbag · Posted: Sat Apr 14, 2012 3:45 pm Post subject:

I'm a bit useless when it comes to developing, as Im out much More basic stuff and more of a builder, but I would love to built one of these. It sounds like a really cool build.

Monobass · Posted: Sat Apr 14, 2012 3:55 pm Post subject:

definitely interested, but don't think I have any skills to put on the table!

frequencycentral · Posted: Sat Apr 14, 2012 4:38 pm Post subject:

Interest!

stahlblau · Posted: Sun Apr 15, 2012 9:27 am Post subject:

sounds cool

nathanxl · Posted: Sun Apr 15, 2012 9:54 am Post subject:

Showing interest in this as it looks cool. I wish I was able to code Arduino.

bonusplays · Posted: Sun Apr 15, 2012 1:03 pm Post subject:

Definite interest!

surgesg

lazerkind · Posted: Sun Apr 15, 2012 2:00 pm Post subject:

Nice code, I've seen much worse from people who get paid for being programmers hihi

As greg says, more bits will not decrease your aliasing, you just get finer steps in your output wave. Some steppyness should be possible to remove with a simple lowpass filter though.

I suspect you get som stepping from the slow analog read so try to speed that up by adjusting the prescaler.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1208715493/11
(I usually get strange readings below 16)

And the standard digital read/writes are not very fast either so either use port manipulation or some ready made functions.http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267553811/a ll

Good luck

surgesg · Posted: Sun Apr 15, 2012 2:03 pm Post subject:

You could also smooth out the analog reads by keeping a running avg of the inputs. I did that on the tabulaRasa inputs and it smoothed out lots of jitter and jumpy values.

zomgw00t · Posted: Sun Apr 15, 2012 6:02 pm Post subject:

It'd be really cool to display waves on a little display like one of these:

1.8" 18-bit Color TFT LCD Display

OLED Breakout Board - 16-bit Color 0.96"

reve · Posted: Sun Apr 15, 2012 11:46 pm Post subject:

Here's a couple videos that better illustrate the concept.

First some oscilloscope action. These are outputs 1 (0 degrees) and 8 (315 degrees). As we go vc phase you'll see output 8 go from 0 degrees out of phase to 630 degrees out of phase. In this video you also see the jagged "aliasing" I'm talking about at the end as I crank the phase knob fast. That may go away with adequate filtering, though.

Second, we have the module controlling LEDs with a little narration. Seeing it beats me trying to type it. You don't see the full effect because we're going from 0-5v to light up LEDs instead of -5 to 5v, but you should get the idea.

lazerkind · Posted: Mon Apr 16, 2012 4:04 am Post subject:

Those jaggies on the second sine wave are not from Aliasing.
it looks like it is due to the wrong values for the sine wave are looked up.
I'd suspect a bad wrap around on the phase counters.
(I did something similar on my Arduino osc, but on purpose, it sounds cool lol

)

JJ · Posted: Mon Apr 16, 2012 5:28 am Post subject:

Interesting project!! Very cool!

Hmm.. Not to derail the talk, this project should of course focus on the main phase-offsetted octature theme... but maybe different modes could be added (within arduino limits)? I mean eight tempo synced LFOs doing quarternotes, dotted eights etc wouldn't be a bad additional mode, plus whatever we can come up with..

I'm not much of an Arduino programmer myself, even if I have managed to make an functional Auduino with some modifications to the code, but I'm sure that if we all work on this one together, magic happens!

reve · Posted: Fri Apr 20, 2012 1:50 am Post subject:

skipperdean · Posted: Fri Apr 20, 2012 2:11 am Post subject:

i really should keep up with the diy thread more. good stuff!!!

reve · Posted: Fri Apr 20, 2012 2:16 am Post subject:

bonusplays · Posted: Fri Apr 20, 2012 2:19 am Post subject:

So rad!

Seems like it would be pretty easy to breadboard provided I could get an AVR inclined friend to help. I'd be happy to wait for the PCB though, if that's where you're headed. Want to support this project any way I can.

Might be really cool to have bi-color LEDs on a module to indicate polarity if possible.

reve · Posted: Fri Apr 20, 2012 2:42 am Post subject:

raisinbag · Posted: Fri Apr 20, 2012 6:22 am Post subject:

so could the 528 give you possibility of 0-5v and -5v to +5v ???? Would be sweet to flip and switch and have both options.

reve · Posted: Mon Apr 23, 2012 12:20 am Post subject:

akrylik · Posted: Mon Apr 23, 2012 1:00 am Post subject:

raisinbag · Posted: Mon Apr 23, 2012 6:29 am Post subject:

Ya for sure. Maybe even a second switch to take signal before or after a voltage divider so you could switch between 0-5 and 0-10. Have you cake and eat it too!!!!

samuraipizzacat29 · Posted: Mon Apr 23, 2012 11:49 am Post subject:

interest and a bump smile

cleaninglady · Posted: Mon Apr 23, 2012 9:02 pm Post subject:

Interested ! Really , really cool. This is fun!

limpmeat · Posted: Tue Apr 24, 2012 1:24 am Post subject:

mega interest.

raisinbag · Posted: Thu Apr 26, 2012 5:33 pm Post subject:

So when pcb is ready will it need an actual arduino as part of each module? OR one arduino to program a chip for each module?

reve · Posted: Fri Apr 27, 2012 2:38 am Post subject:

reve · Posted: Fri Apr 27, 2012 2:57 am Post subject:

Actually, let me follow that up with another question since this is really the only thing left:

What's a useful time range for you guys? Right now it ranges from about ten seconds to 2hz. I could probably add a switch to allow 2-20hz as well? Or 2-60hz? I wouldn't use it but maybe you might. razz

lazerkind · Posted: Fri Apr 27, 2012 4:20 am Post subject:

Nice progress reve,
What are the buffer issues you mentioned?

mono-poly · Posted: Fri Apr 27, 2012 4:29 am Post subject:

Interesting!

raisinbag · Posted: Fri Apr 27, 2012 7:36 am Post subject:

Cheap ass sounds good! Did that come out right?

Well that sounds great, if you were to supply funky hard to find parts that sounds good. I may try to make the chip myself and get an arduino, I would like to learn how to do that, I have avoided it so far.

As for time scale, I say the more options the better. Are you saying a ten second period for 1 full wave? That is so cool. It would
Be great to have option of a ten second all the way to slight fm capability. Am I asking for too much?

Your digital thing sound interesting!

reve · Posted: Mon Apr 30, 2012 1:54 am Post subject:

rowman · Posted: Sat Jun 16, 2012 12:36 am Post subject:

Hey how is this going?

HueMonContact · Posted: Sat Jun 16, 2012 11:07 am Post subject:

I'm really interested in this project! Hope this one gets released soon!
Great work.

raisinbag · Posted: Sat Jun 16, 2012 11:28 am Post subject:

Ya I have been silently obsessing about it as well. But happy it hasn't been released yet as I have blowen the budget on so many other cool builds and want to build like a hundred of these. hihi

One question, what is the main ic? Is it a atmega328?

reve · Posted: Mon Jun 18, 2012 7:19 am Post subject:

Guys, I'm sorry. I totally got sidetracked by my oscillator project. You know how it is. The stuff that actually generates neat noises sucks you in... and the utility modules suffer silently neglected at the back of the workbench. razz

(BTW, the oscillator is at http://www.muffwiggler.com/forum/viewtopic.php?t=61852 if I can distract you with that as well...)

I need to redraw & verify the schematics, layout the boards and do prototypes. Unless someone else wants to layout the PCBs? I'm kind of blundering around in the dark here so if someone who has a bit more experience in such matters would be willing to lend a hand, that'd be super-cool. smile

lazerkind · Posted: Mon Jun 18, 2012 10:17 am Post subject:

My opinion is that you learn a lot when blundering around in the dark, cool

There is some learning curve for doing your own PCB's but after that it just gets easier. at least that is my experience so far with my PCB's.

I'd recommend that you download the free eagle version and get started with that, and if/when you hit a snag, just ask and I'm sure there are lot's of people here who can answer and give hints.

fletch · Posted: Mon Jun 18, 2012 11:55 am Post subject:

Very cool. I'm just wondering where you found the library <digitalWriteFast.h>? It doesn't seem to be available on the Arduino website. thanks!