Communicating between 4x Pro Mini Atmega328P 3.3V 8Mhz and raspberry pi?

I would like to send sensor data from 4 units of Arduino pro mini (Atmega328P 3.3V 8Mhz) to raspberry pi.

If i have the Pro mini 5v version, thent i could use RS485 to create a network and send data over simple twisted pair.

But what to do when i have 3.3v?

Use a 3.3V powered RS485 buffer?