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Post by rodney on Sept 10, 2019 22:20:10 GMT
Hi all, Littlebits are a great electronic system construction kit for kids but I also use them for rapidly prototyping ideas for IoT thingies. Due to a neat partnership with Korg, Little Bits also have a synth kit that features oscillators and filters based on the old MS20 design and they do sound mighty fine.
I plan to make a mounting board so I can easily use the littlebits modules with my AE modular. Below is my first stab at the board's layout.  __ 
I'll 3d Print this and make the files available if anyone else happens to have LittleBits around their place and can safely steal them from their kids.
I plan to glue or bolt the electronic parts to the plastic body for the first version.
Littlebits are all 0-5v for both power and signal, so wiring them in is easy. The one problem I can see is that LittleBits, in order to use less wires, have a weird way of handling triggers. Triggers are achieved by making the CV go briefly to zero whenever it is time to trigger something. That means that anything that generates both CV and triggers in LittleBits, (sequencer, keyboard) will do this. All the other bits (oscillator, filter etc.) should behave much like any other AE module.
Any circuit ideas to handle triggers are most welcome. I have only just begun to research this part of the project.
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Lugia
Wiki Editors
Ridiculously busy...ish.
Posts: 556 
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Post by Lugia on Sept 11, 2019 1:17:14 GMT
S-trig, hm? Yep, that's very MS-20. Both Korg and Yamaha analog synths use that negative-going trigger/gate method, as does Moog (but, historically, not as well-behaved). I know there's solutions to this in the Eurorack universe, and something that can handle the trigger inversion for a synth such as a Mother-32 or DFAM, or the MS-20 Mini (like, say, Doepfer's A-165) should also work perfectly once the signal gets piped back into/out of the AE patchwire environment.
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Post by rodney on Sept 11, 2019 3:20:11 GMT
 I'm guessing that, for processing a littlebits signal to AE, a sample and hold with comparator could get ris of the zero-volt part and just keep the CVs. I'm googling around for circuit examples to try out. In the opposite direction (AE to LittleBits), I'll have to merge the trigger and CV together and somehow multiply the voltage by either zero or by 1, depending on trigger state.
My electronic knowledge is patchy but this is a fun way to learn!
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Post by rodney on Sept 13, 2019 5:59:53 GMT
Okay, just googling around some more.
The littlebits CV module seems to do what I want to do here.
Looks like they use a MCU to do the dirty work.
simplest approach might be an ATtiny with some circuitry to smooth out the PWM output into the desired voltages. but maybe not so accurate? 1~256 different voltage values over 5 octaves, I guess? Adding a DAC would be tighter.
Perhaps the Teensy LC might be better for this, although bumping the price up quite a bit.
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Post by rodney on Sept 29, 2019 10:31:06 GMT
Anywayz...
So far, I've cooked up a 3DPrinted AE module mounting plate on which to mount LittleBits modules and connect them up to AE modules.   Next, I plan to make some jumper-lead adapters to connect to the headers.
If anyone else happens to have some littlebits synth modules around, let me know and I'll link to the CAD and STL files to make this baseplate module. I want to tidy them up a little before linking, but I will hurry it up if you want to print one out.
I don't actually have my AE Modular yet, but it has shipped and should be here in a week or so. I would recommend waiting until I can test on the real thing before starting your own print (took me about 6 hours but I am probably running slower than needed).
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Post by rodney on Sept 29, 2019 10:31:34 GMT
Anywayz...
So far, I've cooked up a 3DPrinted AE module mounting plate on which to mount LittleBits modules and connect them up to AE modules. Attachment Deleted Attachment DeletedNext, I plan to make some jumper-lead adapters to connect to the headers.
If anyone else happens to have some littlebits synth modules around, let me know and I'll link to the CAD and STL files to make this baseplate module. I want to tidy them up a little before linking, but I will hurry it up if you want to print one out.
I don't actually have my AE Modular yet, but it has shipped and should be here in a week or so. I would recommend waiting until I can test on the real thing before starting your own print (took me about 6 hours but I am probably running slower than needed).
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Post by rodney on Oct 23, 2019 11:35:48 GMT
First test of LittleBits module.
A few details to iron out but, basically, it works and sounds great.
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Post by rodney on Oct 23, 2019 20:52:34 GMT
One major stumbling block is that I just assumed that any machine-pin female header would work with the new patch cables but, actually, these snap-off ones do not. Time for some de-soldering (again!).
However, as a proof of concept, it's going well and I love the sound of that Korg MS style filter design.
I may experiment with making the whole thing slightly recessed to make it protrude less compared to other components. However, that may cause its own problems and make it too fiddly to work on. This would apply to other prototyping board modules as well.
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Post by rodney on Oct 23, 2019 21:02:41 GMT
I have not yet started work on a circuit to separate out the CV from Gate parts of the output from the LittleBits Keyboard and Micro Sequencer modules. However, all the other modules should work fine and, I think the Envelope module (envelope and VCA together) will still trigger with an external gate input.
I'll post some more video and sound once I have made the next iteration in the design.
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Post by rodney on Oct 28, 2019 0:52:16 GMT
I swapped out the headers for the old-style ones from my parts drawer and installed it to my AE Modular.
Here you can see a LittleBits Korg-style oscillator wired straight to the output amp. It's just a little portable speaker recorded through the device mic for all these videos but it should give some idea of the character of the sound.
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Post by rodney on Oct 28, 2019 1:12:50 GMT
Here are videos of the Littlebits Servo module controlled by AE's LFO. ( robertlanger, I think you can see where this is heading? ).
An added bonus is that electromechanical stuff, such as motors and servos, adds audio interference and can be heard through the speaker, creating some fun new sound sources not commonly found in your local modular shop.
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Post by rodney on Oct 28, 2019 1:34:58 GMT
... and a couple of pictures of the completed thing, showing the results of soldering-first-then-changing-my-mind. Lucky I have a nice brutal Hako de-soldering tool on hand.
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Post by rodney on Oct 28, 2019 1:39:08 GMT
For the next iteration of this one, I want to put the +ve and Gnd connections further apart to reduce possibility of magic-smoke-release events.
I have yet to set up some circuitry to deal with Littlebits' weird triggering and some buffered outputs and other general housekeeping.
I'll also make some refinements to the 3D printing files before sharing them.
However, this is pretty usable and it's great to have that Korg sound, along with other odd-ball stuff easily accessible right there in my rack.
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Post by slowscape on Oct 29, 2019 18:49:37 GMT
Now this is cool! What a unique idea for a module!
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Post by rodney on Nov 13, 2019 10:25:36 GMT
Here's a 4 minute noodling about with my AE and Littlebits. In this one, I'm just making a single synth voice with the littlebits and controlling them with the sequencer. That's the main sequenced Korgish riff at the beginning.
The other voices come from the AE and grab some of the sequencer voltages via the S&H module and triggered by the Triq module.
I'm planning to take this synth out busking tomorrow, weather permitting. |
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Post by rodney on Nov 16, 2019 7:24:05 GMT
and ...
I moved my modules around a bit so I could blu-tak some plain LittleBits mounting board. I'm getting some weird behaviour under battery power when I use the bus + and ground connections with the LittleBits (it shuts down the moment I connect it so there may be a short somewhere) so I'm powering it from the USB Power module instead.
Here's a photo of my busking rig with only AE modular with LittleBits modules and a crate Taxi amp. I took it out for a mid-morning busking session along the old goods line pathway near central in Sydney and made $7. I figure that is enough  for some more patch cables (or cover my bus fares for the day) and officially makes me a professional!
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__ 
I'm guessing that, for processing a littlebits signal to AE, a sample and hold with comparator could get ris of the zero-volt part and just keep the CVs. I'm googling around for circuit examples to try out.
