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.
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.
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!
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.