Multiple I2C devices with Raduino
Rob French (KC4UPR)
I am looking to have multiple devices communicating via I2C with my stock Raduino. Currently, I have of course the Si5351 on the Raduino, and I also have an I2C backpack on my slave. The I2C backpack is a 5v unit, so I have removed it's onboard SDA/SCL pullup resistors, and so it shares the two 2.2k resistors on the Raduino.
I am about to add a Teensy 3.2 into the mix, communicating as an I2C slave with the Raduino. The Teensy documentation mentions that external pullups are required when using I2C. I *think* this can also be the 2.2k resistors on the Raduino, but I just want to make sure. Am I correct? (Essentially the Teensy would be hooked up similarly to the second Arduino in this KD8CEC drawing, albeit with additional functions.)