Wiring the Raspberry Pi adapter(s)
Your AIS receiver should have two outputs for NMEA 0183 - transmit and receive. These need to be wired directly to the two connections on the RS485 to USB adapter.
If you are also connecting your GPS receiver, this will also have two NMEA 0183 connections for transmit and receive. This will need to be wired to another RS485 to USB adapter.
Connect the USB adapters to the Raspberry Pi.
The Raspberry Pi must be powered from a USB
power source. I use a USB adapter connected to a cigarette lighter
type connection on board. You can also get USB connections that can
be wired directly to your boat's 12 volt power supply.