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Need help with building a CV to OSC Raspberry Pi gadget!
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Need help with building a CV to OSC Raspberry Pi gadget!
waveglider
I have an idea to build a standalone box that takes 16 analog CV inputs and convert them to OSC that can get sent over wired network or wifi using a Raspberry Pi 3 B+

Here's the criteria:
-Uses MCP3208 ADCs
-Need a way to take in both bipolar and unipolar cv
-Scale input levels and assign to specific OSC messages
-Either have an onboard 7" touch screen or remote method of setting parameters

I'm looking for help with coding the software and some basic assist on how to design the input circuitry to handle modular levels going into the ADC.

If anyone has knowledge in these areas that can impart some wisdom it would be super helpful! I think this would be a great tool to integrate modular into other platforms like Touch Designer and I haven't really seen anything out there that is an all in one package like this.
mxmxmx
fwiw, there's a bunch of CV to OSC (and vv) modules that should mostly get you there (there's probably more, idk):

https://github.com/pingdynasty/OpenSoundModule
https://www.modulargrid.net/e/instruo-aither
https://github.com/jakplugg/motivation_radio_hardware

none of them as far as i can tell use a rpi, if that's a given (there's so much IoT stuff ... *), but both "motivation radio" and the rebeltech one are open source. the former actually uses a MCP320x ADC, so that's probably the more relevant in terms of hardware / input circuitry **, you'd just have to scale up to 16 inputs + add a few things, depending on what "a way to take in both bipolar and unipolar cv" implies, exactly (ie is there a toggle switch to switch the range? or would you want to set the input range in software? or perhaps "bipolar" is ok for both purposes?).

IIRC the "OpenSoundModule" runs a little webserver thing for configuration purposes, Aith─ôr also comes with an app. a dedicated 7" touch screen just for configuring some OSC messages almost sounds like wasted effort (to me); at any rate it could always be added later.


another idea (if "scaling" included attenuators / so you can leverage the panel / case design) would be to start with an existing and suitable-looking thing such as https://github.com/16n-faderbank/16n, throw out everything you don't need (DAC/CV out), and replace with what you need (ADC/CV in) + add a cheapo wifi module such as this one (or use a wifi-capable thing in the first place (not a teensy), e.g. the espressif or particle stuff used by above modules)

also fwiw, there's a fairly simplistic OSC client in the "terminal tedium" repository (here). it simply polls the MCP3208 and sends the data out via OSC.


*
the choice of which i suppose somewhat depends on your detailed requirements (e.g. sample rate, how much clock jitter can you stomach, ...); for the purposes of converting to OSC, this sort of considerations probably don't matter much though. (same goes for the ADC chip)

**
if "standalone" = doesn't have a -12V (or -15V) rail, this kind of MCP600x based input circuitry needs to be biased differently, see e.g. here (figure 4).
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