I2c cable newbie question

I received a Teletype yesterday and I would like to connect it to my ER-301, Just Friends and (lower priority for now) Ansible. Teletype comes with its single connector 2x3pin i2c cable and I’ve made a cable for the ER-301 using female breadboard jumper cables.

Since I would like to be proficient with the setup by the start of February I would like to hack around a solution (a backpack from monome or @bpcmusic would be the perfect solution, but it’ll take a month to arrive, so it’s out of the game for now) to connect both the ER-301 and JF.

Communication between the Teletype and ER-301 works via 3pin jumper cable. I’ve tried connecting another 3pin jumper cable to the remaining pins (the other 3pin row of the connector behind the Teletype) but this does appear to freeze the Teletype whenever I issue a JF.x command.

What am I doing wrong? Do you have any other readily hackable solution?

Thank you, I hope I’ve explained it correctly :slight_smile:

as long as the GND, SDA, and SCL pins are lined up correctly it should work. freezes will happen if the cable is reversed (connections are incorrect)

also perhaps try connecting just the TT to JF and test.

there’s a good change with just raw wires and multiple modules you’ll need more pullup resistance. the tt busboard solves this, or you can mod your TT by swapping the resistors that are on the pcb (they are 0603 smd)

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I just tried connecting both cables to both the 3pin rows of the teletype connector. Both slave modules work.

This makes me laugh uncontrollably. Thank you.

Somebody in this conversation is a genius and it’s not me.

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Just another question that popped into my mind. Can I use the second 3pin row on the back of Just Friends as a passthru for i2c communication to Ansible? :thinking:

yep. it’s a bus. you just need all the points connected, like a passive mult

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I’m slightly overwhelmed now. I just can’t understand why I haven’t bought a teletype before. So many possibilities. A lifetime of exploration. This is so great. Thank you @tehn


Things I have learnt in the weekend (archiving here for posterity).

  • with the exception of the ER-301 all modules supporting the i2c bus have 2 rows of 3pins.
  • you don’t need to use both rows: you can use only one 3pin row for i2c communication to work.
  • you can use the other row on the teletype to connect to another module.
  • you can use another module with 2x3pin i2c connector as an i2c passthrough (i.e. if Just Friends is connected to Teletype with a 3pin jumper cable, you can connect another 3pin jumper cable to the second row of JF to one row of Ansible, and Teletype will communicate with Ansible too)
  • beware of orientation. the ER-301 has a different pinout; Ansible has the connector upside-down. Always read the legenda before connecting :slight_smile:

About to try this with a backpack attached to TT.

I am using raw colorful wires so orientation seems easy enough.

EDIT: I still got Ansible wrong. Double checked before powering on :stuck_out_tongue_closed_eyes:

Can I use any row of 3 x pins on the backpack to connect any other unit or does the choice of row have any implications?

There’s mentioning of passthrough, the JF for instance has its rows marked as row 1 and 2. Are they interchangeable? (I’m connecting pin row 1 to some unspecified row of pins on the TT but worried about powering up yet)

EDIT: No problems with the above. :smiling_face_with_three_hearts:

Will raw wired fall out and cause trouble, like under transport? They seem very well fixed and the cable connectors are rather deep so I don’t believe they would.