Quick update on the Teensy 4.1:
My initial tests with T4.1 and i2c2midi were successful, using a different I2C library.
There are some minor hickups when sending values back to TT, which I still have to sort out – but overall it looks promising.
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Knivtid
308
This is great news! Would this be working with a i2c2midi mk2 pcb, maybe with some modifications?
Yes, no hardware changes needed.
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Here is my Mouser BOM that I used to successfully build a mkii version.
Mouser project
If you cannot get to it, let me know and I’ll delete this message - no idea how to share a project with lots of people. No idea how to convert a project to a BOM either.
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Thanks a lot for sharing your mouser cart @Gerald_Stevens – that’s very handy!
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i2c2midi_MOD_DOC.pdf (1.0 MB)
Hi! I did some mods for i2c2midi and Intellijel Palette and documented in this PDF.
I made it in a rush and it’s pretty rough, also it’s very empirical so there might be technical errors I’ not aware of. So if you see anything wrong please report and I will update the documentation asap.
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@Erekutoronikku Wow, really nice documentation! Congrats!
This is awesome. All these different contributions are absolutely fantastic and very much appreciated!!
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Teensy 4.1 support
I am really happy to report that i2c2midi now works with Teensy 3.6 and Teensy 4.1. 
I have just uploaded a new firmware version (4.1) to the repo which works with Teensy 4.1:
https://github.com/attowatt/i2c2midi/tree/main/MKII/firmware/i2c2midi_firmware_v4_1_t41
You can use #define TEENSY36 or #define TEENSY41 in line 51/52 of the i2c2midi_firmware_v4_1_t41.ino file to chose which Teensy model you want to use.
In order to build the firmware for T4.1, you’ll need to add this library:
https://github.com/attowatt/teensy4_i2c
(It’s a slightly changed fork of the original library)
I haven’t had the chance to test this extensively, but it is working perfectly as of now. Nonetheless, would be awesome to have some additional beta test reports!
Many thanks to @gotascii who helped with the implementation and found the solution to some I2C reliability issues we were facing with the I2C library for T4.1.
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Hi i’m having a problem compiling for a mk 1 using v4 firmware
i get this error
I also tried the ready made hex. I only 1 light showing i2c from teletype being received. The midi out light does not light.
I also tried v4.1 which compiled ok - with no red errors - but still the white messages. Still only getting 1 light flashing instead of 2
Did you remember to do this?
yes i did - i commented out mk2. I also used the premade HEX and get the same issue with only 1 light. I had this working fine on the previous v3 firmware.
Just tested it succesfully with my MK1, using i2c2midi_firmware_v4_1_t41.ino:
line 35:
//#define MK2
line 51 & 52:
#define TEENSY3X
//#define TEENSY41
You can ignore the white warning messages when compiling 
It should work regardless.
Edit: Better don’t use the HEX, because it’s compiled for Teensy 3.6.
yes i did the line 35, line 51 previously - i get no red errors and it uploads successfully
i compiled the v4.1 again - (i had previously added the additional library) with the same result - just 1 light
is there anything specific in teletype i need to switch on - i just put some random cc in an M script set to midi ch 1 - just so i could see a light flashing - i have the teletype beta installed
Just to be exact: Do both LEDs light up when powering on? If yes, all is good.
Since firmware v4 the LED behaviour changed during operation: second LED only lights up for MIDI in.
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yes both light up on start up. the 2 lights are at the top. So maybe it is working? i have been trying to receive cc on a h9 with the correct midi cable but not getting anything maybe something I’m doing wrong in the h9 setup. i’ll dig around with some other midi stuff. Thanks for your help 
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@mlogger So I figure you found the issue?
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Yes - what I did to fault find was hook up the i2c2midi directly to midi monitor snoize: MIDI Monitor on my computer so I could see exactly what was going on - which was nothing! - that was with 3 different cables - 2 of which were labelled type A on the bag. When I tested the pins with a voltmeter they weren’t type A.
The only cable that worked was the “real” type A from a Polyend Tracker - the random cc sent was picked up on the midi monitor…
the h9 is going to get a serious workout over the coming months - the multi tap delays / pitch shifters and reverbs especially, but also the clocked looper. Having voltage control of the 10 main parameters as well as all the switches / hot knob is a godsend.
Thanks for your help!
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ka8ong
324
I feel silly asking this, but how would I go about getting norns to recognize and send data to i2c2midi MKII’s USB input? I’m able to receive MIDI from an outboard synth into i2c2midi/TT just fine; norns just doesn’t recognize i2c2midi. Is the problem is that both devices are acting as USB hosts?
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Yea, definitely don’t plug two hosts into eachother without a device in-between! The micro usb port on the teensy can be plugged into norns though, that’s what I do on my MK1. You might need to change something in the code to make this work though, I’m not sure.
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I am more than happy to help!
As you suspected, it doesn’t work because i2c2midi and norns are both acting as hosts.
If you want to send MIDI from i2c2midi to norns …
As @nonverbalpoetry already mentioned, i2c2midi can also act as a USB device, using the USB port on the teensy. This port is not accessible through the front panel, so you have to build/hack/diy something to access the port.
You can activate the usb device feature by removing the two slashes in the i2c2midi_firmware_v4_0.ino file:
//#define USB_DEVICE
When you compile the code using Teensyduino, make sure to select Tools → USB Type “MIDI”.
Important: Do not connect Teensy USB and Euro Power at the same time! Cut the 5V pads on the Teensy! More info about that here under “option #1”.
If you want to send MIDI from norns into i2c2midi …
I actually never tried or tested if this would work with the Teensy USB port. Let me try and get back to you about this.
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