3v3 and 5v Logic levels

I’m not sure this is the right part of the forum for this but it is Arduino-adjacent.

My plan is to use my Daisy Seed as part of my homebrew modular synth, but it is largely based on a bunch of Arduino nanos serving as both sequencer, oscillators, LFO and so on.
This means that the system is pretty much all 5V.
Will the 5V signal levels be a problem for the Daisy since it’s 3.3 volts?
For instance if I use the Gate pulse from my sequencer to trigger an envelope in the Daisy or if I want to send a CV from my LFO to the Daisy to modulate a filter?

The problem with the gate pulse isn’t that hard to solve since I can just put a voltage divider at the source and lower it to 3.3V but I’m guessing the CV might cause a problem since the Daisy has a 3.3 V reference voltage.

Hey @Saotome,

sounds cool! Would love to hear some of the stuff you built already!

Don’t fry your Daisy Seed with 5V inputs; have a look at the schematics for the patch: https://github.com/electro-smith/Hardware/blob/master/reference/daisy_patch/ES_Daisy_Patch_Rev4.pdf

In the Section GPIO and CV In, you can find two good examples of how to keep the inputs from going over 3V3. In GPIO, the MMBT3904 feeds 3V3 to the Seed’s pin if a trigger / gate is present on the input jack.

In CV In, the 3V3 powered MCP6004 saturate at their VDD voltage, 3V3. The input voltage range can be scaled beforehand but the actual voltage to the pin clips at 3V3.

I hope this helps!

I’ll make a video one of these days and post here. It’s really a mess since I started building it before I knew the first thing about modular synthesizers.
Hm, I think it might actually be easier to just redo my setup to use 3v3 levels.
As I said, the gate pulse can be lowered with a simple voltage divider at the source and since my LFO and Envelope generator uses DACs to generate the signal I can just adjust the range of those to 3v3.

I guess my sequencer and oscillators would have to be fixed as well but since the arduinos have a 3v3 out as well it would work.

@Saotome Buffering the inputs and outputs is good practice in modular synthesis - the idea is that you can’t overload your pins and damage your MCUs.

It’s also something you should consider for your Arduino projects (if you don’t already) - if you combine your 5V projects with other modular gear, e.g. Befaco, you might see 0-10V CV, or if you passive-multiply different signals together, you might get spikes that surpass 5V.

The I/O circuits are very often just a variation on what I linked (e.g. look up inverting and non-inverting amplifier). Try to simulate before you build and you mostly end up with excatly the levels that you need.

I agree it’s some work and sometimes some headscratching too but you will have to repair a lot less : )

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Ok, thanks for the advice :slight_smile:
I’ll look in to putting something like that in place for the daisy.

I doubt I’ll ever combine the thing I’ve built with any actual modular gear though, since it doesn’t follow any known standard what so ever for anything :smiley:
I really made everything up as I went along.
The only bit of it that might function the way someone who knows modular synths might expect is probably my delay effect. It’s based on a pretty standard PT2399 circuit.

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