Nerdseq & I2C & er-301

It makes sense, now that i read it again :wink:

That’s exactly right.

@XOR-Electronics In fact, there are no “global” Teletype commands implemented in the ER-301 at the moment. They are all port-specific.

FYI, port 0 is a diagnostic port which will pulse (i.e. trigger) every time any i2c command is received on any port.

Sorry I missed the question! :bowing_man:


Cool thanks. If you show up at TFOM then i will bring you one working expander prototype!


This then. By removing the screws it can also be mounted somewhere inside the case.


Loving the panel !

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Just a question that some of you can possibly answer:
I implemented note scaling so the note is being set through SET.CV.
I starting with Note 0 → C-0 at 0V, using only positive numbers.Note 1 → C#0 etc…
To calculate the notes for 10 octaves i use 16383/120*note.
120 for 10 octaves at 1V/Octave. All sounds slightly off as if the range is not correct.
Am i using the wrong numbers?

Before we get into your quantization math: When you receive this pitch voltages on the ER-301, do they match the expected values? You can set in ER-301 settings to display “actual value” at a control instead of “bias”. Someone smarter than me might be able to tell you how to best use the ER-301 like a multimeter.

I believe the correct formula is actually 16834/120*note because in my Teletype message dispatcher I have:

static inline float convertCV(int value)
    return value * (1.0f / 16384);

void TeletypeDispatch::commandCV(int delay, int port, int value)
    mCVTarget[port] = convertCV(value) + mCVOffset[port];
    mCVDelays[port] = delay;

but now I’m wondering if that is right? :thinking:

Edit: I think it is right and I remember now why I think that. On the Teletype you can lookup the integer codes for voltages using the V command and when you look up 10V and 5V you get:

> V 10
> V 5

OK that is fixed. Silly me, silly typo. Instead of ‘& 0xff’ i did ‘& 0x0f’. Interresting quantisation, but not the one i want :slight_smile:

All fine now, thanks for the hints. (And using 16384 also now, the docu points to 16383 ER-301/Teletype Integration - O|D Wiki , but i guess no one would ever hear the difference anyway :slight_smile: )


Oops! It’s fixed now on the wiki.

I’ve been using @tomf’s amazing Polyphonic Synthesizer units a lot recently (with Hermod) and NerdSeq’s ability to do 4-note polyphony via i2c would free up tons of modulation inputs on the ER-301.

Could anyone who has owned both Hermod and NerdSeq offer their opinion on how they compare? For example- would I be able to configure NerdSeq’s polyphonic tracks via i2c and still use the modular outputs normally? I’m guessing this would fall under the “flexible assignment of tracks and midi channels” in the v1.19 update. If someone could just point me in the right direction that would be appreciated.


I can’t give you any comparison about Hermod vs. NerdSEQ and maybe here is also not the best place to ask for it, but i can give you some information about the I2C implementation:
First, you can use all outputs from all tracks anyway always and nearly all functions with the outputs for the local tracks will stay as well.
It will indeed be implemented as flexible as with midi or the other expanders.
For the rest i am still early brainstorming of how i would integrate it at best. Of course i think it makes sense to also allow polyphonic stuff, multiple modulations and like the drummatrix with it’s euclidean input etc.
Currently it is a working proof of concept with a lot of potential and of course, i am open for any ideas to make it a nice addition to both, ER-301 and NerdSEQ (and other modules that understand I2C).

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Thanks for the reply. Regarding the Hermod/NerdSeq comparison, I was just referring to the ability to configure individual channels (mono vs poly) via i2c, so your answer cleared it up perfectly.

Super excited to see whats on the horizon! Looks like I’m going to have to pick up a NerdSeq soon :nerd_face:

Bought my Nerdseq because of this thread! Had SO much fun last night with my Nerdseq and can’t wait for this to be released.

My only gripe is that it won’t fit in a pod60! But GREAT move making it detachable/hideable in the case!

@XOR-Electronics Any chance of making a 4 expander bundle available? I’M GOING ALL IN!

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This is a serious question and not an attempt to argue:

Wouldn’t something like the FH-2 be the most powerful tool for sequencing? You can use your computer or phone and whatever full powered sequencer software you wanted? You can use ANY hardware based sequencer (even more than one at a time) so long as you can do midi over USB. (Just use a ROLAND DIN 5 to USB for it, and viola.) As the FH-2 is completely mold-able you can configure the outs in whatever way you want, and not in the predefined ways of hardware sequencers.

How would the Nerdseq or any other eurorack sequencer compare to that?


On another note, if the I2C connection is being used for inputs, does this mean that the physical inputs are still available for other chains? Same question for the NerdSeq? How does the interface handle the I2C lanes?

The NerdSeq is a fantastic lookign sequencer. I watched a Cuckoo video on it, and it really seems like it would be a lot of fun to use.

I agree that a computer solution is much more powerful of course. But there is more than that. Many people prefer completely in-rack. To ask even further, why not using a computer and one of the many virtual modular solutions…why using the ER-301 while you can have sound computers in software where you can see everything you do on the big screen?
It’s all about preferences, it’t about the feeling, it’s knobs, it’s (fill in everything you can think about)

As for the I2C, yes the physical inputs can be used for other stuff then. In the NerdSEQ you get dedicated I2C/ ER301 (and most probably others) patterns.
The cuckoo review is nice, but it shows only barely whats all possible. If you check the sonicvoltage tutorials, you can get a idea of how deep it can get and even these are already nearly a year old and many new features have been added since. And the trigger16 expander video gives you an idea on how expanders (like the I2C in the future) are integrated.

I’m working hard to get it all ready and i think the NerdSEQ->I2C->ER301 combo will something really cool!


Thank you very much for your response! Your passion and enthusiasm for your product is evident and confidence inspiring.

The I2C interconnect between the 301 and the NerdSeq is fantastic.

Could you tell me what limits there are as it seems like the I2C tracks are not limited in the same way as the physical jacks. Is the plan to just saturate an equivalent of what the 301s inputs are? (IE: 4 gates and 12 CV inputs)

That is as much a question to O|D as it is to XOR. Are there plans to allow one to go beyond what is currently possible in that regard? IE: the 301 could handle 32 inputs and 12 gates via I2C, instead of the 4 and 12 respectively.

There is already some documentation around and you can have much more than these. I implemented already the NerdSEQ drum-matrix which are already 16 gates and they are many more possible. The big question is, how many makes sense and still fit into the user interface.

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I said ‘in eurorack.’ FH-2 with a computer or phone is not in euorack its a external device with a midi to cv converter.

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Are you using any kind of external control or midi device? You see where I’m going.

FH-2 is a device that only works within Eurorack. Whether I plug a midi controller up to it, or my phone running a midi sequence doesn’t change that. You might split hairs on that, but I don’t.

At the end of the day, it’s certainly not something to argue about.

The NerdSeq is pretty great.