Please note: The ER-301 does not ship with i2c cables. Here is some info on how to DIY your own cables: DIY i2c cables @ LINES forum.
In a nutshell, i2c requires 2 communication lines (SCL and SDA) plus 1 ground line. So there are 3 pins on the Teletype that need to be connected with a custom cable to 3 pins on the ER-301. Along the bottom edge of the ER-301, you will find an I2C header with 3 pins labeled as GND, SCL, and SDA. Please connect those pins to the same pins on the Teletype as follows:
- Teletype GND to ER-301 GND.
- Teletype SCL to ER-301 SCL.
- Teletype SDA to ER-301 SDA.
Note that the connections are all one-to-one with no crossovers.