Module requests

that is definitely on the to do list! I’m sorry its taken so long!!! I have a lot of them on the go at the minute. rest assured it will be one of the next wave!! got a mega drone module and 6 channel midi to cv on the way next. then faffing on a delay and a noise crescendo module then lets see!

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Midi to cv would be a miracle for me.

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I agree with @Caustic! I’m in dire need of a midi to cv module. Right now I don’t have a way to use any of the other modules I have. With everything going on is there a way that you could supply a parts list for the midi to cv and VCA so that we could try and get the parts ASAP? Mouser is still shipping right now, but they may not be a week from now. If I’m going to be stuck in my house for 3 more months I’d love to be able to use these awesome modules you’ve created! :smiley:

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You could do a midi to cv module with an Arduino, an optocoupler and a DAC pretty easily, so if you wanted to source the parts, I’d start with Everything in the last section of this instructible Then add a DAC (I like the Adafruit MCP4725 breakout, but they shut down their operation for the time being so unless you can find one aftermarket on eBay or something you may be out of luck.)

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I can pick up an Adafruit MCP4725 here locally. I just checked and the store here has several in stock. They are still open with limited hours. I have all of the other parts listed except for the optocoupler. The one on that site suggests “6N138” but there are several listed on Mouser. Is there a specific one on Mouser you can recommend?

https://www.mouser.com/_/?Keyword=6N138

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6N138 is a JEDEC part code so they all have the same basic specs. Just grab one in the right package (DIP/PDIP for through hole, not SMD).

Note that 6N138 appears in a lot of internet schematics, but strictly speaking it’s not fast enough to match the MIDI spec requirements, even if that probably doesn’t matter for normal use.

(I use 6N137 instead, which is much faster, has a logic gate output instead of a darlington transistor which is nice since you’re connecting it to a logic gate input, and is readily available from Tayda and others. See schematics here.)

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indeed!!! the module I’m making is around the midimuso anyway! which is using an at mega 328, and pretty much all of the pins as Pwm tbh I really am not sure how he has managed it but he has. it has a total of 12 CV outputs and 6 Trigger outputs all from 1 atmega chip. I have used it a number of times for a few projects and decided to use it cus I’m deffo not gunna be able to beat that haha. plus it has extra midi thru’s and bus control etc. I dunno. hopefully that project will be up soon!! but if your not aware of it check out “midimuso”

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This one?

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yep! been chatting to rob about it the person who designed it. and worked on a circuit that works nice in modular. waiting to see if its all come together nicely!

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That’s a little more featured than what I could have suggested with the optoisolator and the DAC. Just looking at the board and not the schematic, it looks like he’s using the 324s as the DACs. I experimented with that once and got about the same iffy results I got just using the PWM last week, but that’s probably down to my build.

@popflier I’d recommend you wait for Sam’s build or try to get one of the Midimuso kits. If you can’t though, I can still give you the basics of how to pull the elements together (which would probably be very frustrating and then very rewarding and then very frustrating again when you grow into needing the six lines you can get from Sam’s version against the maximum of 2 I could help you with on this build.)

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From a very quick peek at the schematics, each channel goes through a level shifter, a first-order lowpass filter (100k/10nF) and a voltage follower. The reference voltage is provided by an LM317. And the opto coupler is a 4N35, which is even worse than the one I complained about above. Definitely a slight “are you sure this is good enough” factor :upside_down_face: but Sam’s tested it, so I guess it does work :smiley:

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There are also some simpler versions available, like this one: https://github.com/elkayem/midi2cv
I made a pcb for that, which I can share, but I have not yet build it and it is therefore untested.
It only has 1 channel, but you could change the software and convert the outputs for velocity, control and pitchbend into V/oct. My plan was to make a ‘polyphonic’ code version, which I can connect to my 4 VCO’s to play chords! I forgot to connect a fourth pin as an additional GATE, but I can still just solder it directly to the arduino pin…

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If you want to go truly minimal, there’s https://www.hackster.io/janost/diy-good-ol-midi-to-cv-d0e2bf (haven’t built it, but if midimuso’s cv-12 works I don’t see why that shouldn’t work :smiley:)

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Ah-now I see the schematic and I wouldn’t have read it right. I’ve never seen a schematic with that many non-right angles. I hope it works!

I’ve got quite a lot of ATtiny85s including some on Digispark development boards. Another chip to watch out for is ATtiny2313 which comes with a built-in UART and a 16-bit timer, though it’s much smaller in flash and RAM. All these chips share the same basic architecture and are compatible with Arduino.

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The 85 “jellybeans” have a million uses and are easy as hell to program, but also limited. I don’t know if they’d have the pins to drive a single ADC with a pin for gate and MIDI in, or if that would require you to dedicate two pins to an external crystal (something I’ve tried and I’m not sure if it worked or not!) If it does work though you’re probably looking at a $6-7 project even after sourcing out a PCB, so it would definitely be an appealing build!

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It would also be neat to have a module that enabled poly mode by taking midi notes, buffering and distributing them across voices via CV at some point. I’ll have to think about it.

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I think that’s pretty much what Sam (and @fredrik ?) came up with for the GBMM, so you’re probably in luck!

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I assume you mean a DAC. The idea is you use fast PWM mode on the ATtiny85, using the duty cycle of the PWM output to vary the effective CV.

ATtiny85 is so versatile that somebody even designed and sells a complete 8-bit modular kit based on identical modules that behave differently depending on their software. It would make a great present for a child interested in learning electronics and playing with synths.

https://minimosynth.com/

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Yup, yup I did. Still not in focus I guess. I’ll have to check out that minimonosynth-I’m fascinated to see how they handled the 1v/oct oscillators if it’s standard Moog levels. Even though I sort of tried to tell myself to give up on the idea of the “budget west-coast” plans after my build this weekend.

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