Intellijel Metropolix, Gx, CVx, Tetrapad & i2c


I’m not sure if everyone noticed but the Intellijel Metropolis successor, the Metropolix, uses i2c to communicate with it’s ‘Gate Expander’ (Gx) module. I inquired over on the intellijel forum if they would be amenable to jumping on the i2c train along with Teletype, Crow, Disting EX, Er-301, Just Friends, W/, etc.

Here is the conversation:

Please help me convince them this is a net positive and brainstorm use-cases. There is no way they are going to jump right in, but if there is some way we can push for a very small, easy to implement function, they may see value in developing more complex i2c control.



Also, apparently Danjel has already asked (and it has been mentioned once on another i2c thread) for the Intellijel 1u CVx module to be supported by teletype. The CVx module could probably go a long way to providing much the same functionality of the TXo.

I don’t have a 1u row in my case or I’d be all over that. Intellijel says you can chain 4 CVx modules for 32 total output channels.


So Intellijel just posted the information needed to control the Gx module…very interesting. The module is 4hp, $69, and offers 8 ouputs!


There are some address collisions with existing modules in the monome ecosystem, but there is nothing else to prevent someone from adding control of the Gx/Qx/CVx expanders to Teletype right now. It would actually be a great “My First Teletype Firmware” development project for anyone interested (not me, but please feel free to PM me or find me on Teletype studies discord for guidance and/or testing).

Metropolix as a follower module would obviously require some undertaking on Intellijel’s part since it is closed-source. Plus it would require Metropolix, a leader module, to coexist on a bus with another leader. Multileader setups are not stable because there is no ecosystem-wide method for coordinating bus traffic. Perhaps someday…

if you don’t have devices with conflicting addresses on your i2c bus, you can use the generic i2c ops added in the latest beta.

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Yeah, good point. In fact I used the generic OPs quite extensively while testing the latest JF OPs. I can’t think of any sugar needed for the CV expander, but the gate expanders might benefit from TR.P-style pinging, etc.

Yeah, I don’t have an Orca, so a Gx w/ generic i2c ops might be in my future!

I wonder if (like 16n) there could be different firmware loads with Metropolix as leader and follower? I would sure like to issue commands to change metroplix presets!

If intellijel would be willing to experiment it would be cool to have the metroplix be the leader for ER-301 and 16n, but that would be a lot of work on their part.

we don’t support it currently for any i2c devices, as it would require allocating additional timers.

I want to say there was a push to get them to implement it on tete + tetra pad as well

the spec is posted here: Tetrapad I2C Specs - Eurorack - Intellijel Forum, so should already be possible to control tetrapad via i2c using the generic i2c ops.

Nice! Thanks @scanner_darkly, this could be exciting. The CV expanders have a lot of potential. I suppose Tetrapad and CVx/Gx would both be followers?

correct, both should work as followers.

Pardon my ignorance, but in the case of the CVx and Midi 1U, are we discussing the potential of hacking a prebuilt midi to i2c converter, or simply additional CV outs?

My understanding is that you can leverage a i2c leader like Teletype (or a crow/ansible et al. in leader mode) to send i2c commands to use CVx as extra cv sends or Gx as extra gate sends IF there was some consideration (in the leader module’s code) of the follower module’s specific needs to receive i2c.

This leads me to believe that it’d be on Intellijel to make their Midi 1U module to convert midi and send to specific addresses on the i2c bus to hit specific follower modules beside their own CVx/Gx modules. So I’d guess that’s not likely at this point since their stuff isn’t as open and they don’t intend to dedicate dev cycles to it.

That said, there’s already a norns script that does this for the specific combination of midi controller > norns > crow > just friends (called Just Play) which is a blast! Oh yeah and you can also do it with just crow and m4l devices…

I may be way off base here too, so take that with a grain of salt, but fwiw, here’s the best post for explanation of the whole ecosystem here

Maybe someone here can fact check me?


Yeah I think for CVx and Gx, I was just thinking of additional outs.

I have offered a couple of use cases for Metropolix as both leader and follower.

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would be amazing if we could eventually use cvx or qx as an expander for the er-301

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