I2c multiplex chip?

8 same-address I2C devices hooked up to one microcontroller - this multiplexer acts as a gatekeeper, shuttling the commands to the selected set of I2C pins with your command.

Looks very cool. Will this be of use?

This is a useful thing to have for the situation described – you have many of the same off-the-shelf device that use the same fixed I2C address. In Eurorack-I2C-land it’s probably easier to just change the address your duplicate follower devices are using – most followers support this either with jumpers or through some user interface, or by recompiling the firmware – rather than involving additional hardware. A device like this would also require firmware changes on the leader side to interact with the multiplexer.

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^ this is all true. would take work to integrate:

  • first, need to have the multiplexers adress, which can only be changed by 2 bits.
  • then, when you want to send something to a “downstream” follower, you gotta preface that i2c message with another one telling the multiplexer which physical follower you want. so for most situations this would be a net increase in traffic on the “upstream” bus.

but… if understand correctly, the TC9548 actually provides 8 different physical “downstream” busses. so for applications like i just saw discussed… uh… here, where you really wanted to broadcast to many devices at once, a device like this would result in a lot less bus traffic for each “follower bus,” and maybe make the difference between feasiblity and non-.


funny you referenced that as I saw that then I saw the Adafruit i2c and I just got. second JF so I have
2 x JF
And I about to DIY a Teletype so I think at a certain point we are gonna need something like this

yeah… that’s… a lot of stuff of course. (though, norns is not an i2c device.)

i don’t disagree that once you get that much stuff, and you want a lot of bandwidth for realtime, vanilla i2c is no longer very suitable and some kind of switching seems necessary to manage bus capacitance.

Michigan Synth Works has been using an I2C repeater chip in their F8R expander which effectively isolates the A- and B-side bus capacitance (usually two cases, or a case plus 16n, etc.). That kind of chip should help with stability but not with overcrowding.

I think we are approaching a time when an I2C router is a desired part of the ecosystem. But honestly I find myself happier when I separate my devices into multiple buses. That may be less of an option for those who lack multiple leader devices though.

I still am wishing for multiple addresses for JF. It should be a relatively simple matter to release an “address #2” version of the (closed-source) firmware. Trent was disinterested in the concept last time I asked but it can’t hurt to have more folks asking.

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i keep dreaming of an i2c device that would serve as an i2c repeater (for connecting sub buses / different cases etc) and in addition would provide necessary pullup values automatically, monitor and display the state of each bus and a way to reset hanged buses, and maybe even a switch to be able to reconfigure buses on the fly. no idea whether it’s technically feasible.

Ive been thinking a lot about this and I cant see another worktable wy around something like this others the II/i2c is gonna get unworkable.

Id be happy to pay for someones package if they wanted to work on it with me

Trill Hub also includes on-board pull-up resistors for the I2C lines, in case your board requires it (like some versions of Teensy), so no extra parts are needed for your setup.

To find out more about the I2C communication protocol and about using multiple Trill sensors together have a look at our all about I2C guide.

The Bela trill stuff looks great - as soon as some pennies become free I’m gonna grab one of these- it’s 10 pound uk monies