I’ve got a pro mini 5v that I used in an old project that is no longer needed, and I want to use it for a new project. I’d like to make it a slave to my raspberry Pi. I’m hesitant to connect the I2c on the arduino to the i2c on my pi because it’s 5v and the pi is 3.3v. What’s the easiest (cheapest) way to bring the i2c down to 3.3v to talk to the pi?