Bidirectional protection or isolation for generic digital communications
You could just use series resistors on the lines, depending on the communication protocols present. That's cheapest. Lots of components already have ESD diodes on their pins so series resistors will stretch those further.

You can also add external TVS diodes yourself but those can cost quite a bit. This lets you get away with a lower resistance since the external TVS can probably dissipate much more power than the pin's internal ESD diodes.







simulate this circuit &ndash; Schematic created using CircuitLab