With a little work and some programming, the Littlebits Arduino bit can communicate with the EV3 brick over I2C. It took me a while to locate all the information needed so I wanted to document the links and additional information here.
Most of the information I needed to connect the computers was on Dexter.com here. Read that article first. Just be aware that there are some differences between the Arduino One used by Dexter and the Littlebits Arduino. The Dexter example uses pins A4 and A5 for I2C SDA and SCL, the Littlebits Arduino uses D2 and D3.
You will need to purchase the Dexter EV3 breadboard adapter here and install the Dexter I2C EV3 blocks on the computer you use to program the EV3 brick.
You will also need to solder headers to D2, D3 and ground, then connect those to the Dexter I2C adapter. My solution looks like this:
There is more information about how to modify the Littlebits Arduino here.
Note that I did not connect +5V to the EV3 adapter. You can easily do this and then the Littlebits Arduino will be powered from the EV3 brick. I found it more convenient to control their power separately while I was prototyping so I didn’t do that.
Finally, before the code will work on the Littlebits Arduino, you have to disable to pullup resistors on the Dexter EV3 adapter. There are two dipswitches on the board –make sure they are turned off.
That’s about it. The code from the Dexter link above worked first time once I had the pullups right.
I think I can wire a more elegant solution using the perf bit. If I get around to doing that I will post a picture here.