It might seem odd to start a treatise on level shifting this way, but the first question for the designer when looking at making a 3.3V part talk to a 5V part should be this: Do I even need a ...

but some of them can only operate at 3.3V while the rest are hungry for a 5V connection. What to do? [Linux-works] built this I2C level converter to solve the problem. The circuit comes from an ...