It is not so much protection against lightning, that immunity to radio-frequency interference for long lengths of cable. Indeed, with an optocoupler, we are in the presence of a symmetrical connection with a strong current. NMEA provides a current of 4 mA.
The other important point is the elimination of problems potencial differences between the sensor and the micro-pross. For example, the sensors can have a different power supply from the power supply Micropross.
In the case of a short length of cable between the sensor and the Micropross we allow our sensors to connect the NMEA signal OUT - to the UART Rx Micropross.
Christophe
CV7SF-RaspBerry_Pi-ENG 200314.pdf (151 KB)