I'm having difficulties with communication between the EV3 and Arduino boards. Does anyone know if the EV3 is really I2C compatible, or is it just close enough?
Background: I can get the EV3 to send and receive I2C with an Arduino Uno, but not with MKR1000 or Adafruit Huzzah boards. This is both with and without pull-up resisters, and also trying different values of pull-up resistors. When I scope the SDA line, it look reasonable when communicating with the Uno. When communicating with the MKR1000, the low logic level only reaches 1.6 V (with the 4.7k resistors desoldered from MKR1000 board, but looks worse with the pull-ups). With the Huzzah board, the SDA line looks great for about 4-5 bits, but then also raises the logic low level to about 2 V. The clock line looks clean no matter what it is connected to.