This multiplexer allows the connection between your Nmea 0183 or SeaTalk1 instruments and your smartphone, computer or chartplotter, through WiFi or wired connections. The system has 2 opto-isolated Nmea 0183 input ports and one Nmea 0183 output port as well as an input/output USB port. It also has a bidirectional SeaTalk1 port that can work as an input or as an output. Data received from the SeaTalk1 bus is converted to Nmea 0183 sentences, Nmea 0183 data can also be converted to SeaTalk1 datagrams and send on the SeaTalk1 bus. WiFi communication supports both the UDP and the TCP internet protocols. In total there can exist 5 input streams of data (2 serial, 2 WFi and 1 SeaTalk1) and 4 output streams of data (1 serial, 2WiFi and 1 SeaTalk1). The 5 input streams can be filtered, combined and routed to any of the 4 outputs streams. Filtering is possible on Serial and SeaTalk1 outputs. The multiplexer can also be used as debugger or analyser of the data that travels on the SeaTalk1 bus.


Microcontroller: ESP32 (2 cores – 4MB – 240 MHz)
Power Supply Voltage: 7V up to 16V DC
Power Consumption:
   less than 90mA with Wifi ON
   less than 10mA with Wifi OFF and Serial OFF
Nmea 183 Input Ports: P1 and P2 - optically isolated
Nmea 183 Output Port: P3 - RS-422 compatible
SeaTalk1 Port: input and output (fully bidirectional)
Baud Rates:
   P1 and P2 = 4800, 9600, 19200 or 38400
   P3 and USB = 4800 , 9600, 19200, 38400, 57600 or 115200
Nmea 0183 Sentence Filtering: serial inputs and output and WiFi inputs
SeaTalk1 Datagram Filtering: on input and output
Firmware Update: Over The Air (OTA) without cables
WiFi protocols: UDP and TCP
Other: operation in Simulation mode or Debug mode


Before installation and to get acquainted with the multiplexer, you can power it from a computer solely with an USB cable. You can get access the WiFi network described below, choose Simulation Mode and try to receive simulated instrument and AIS data in applications like Navionics , OpenCPN or others. You can power the unit from a 12V power supply or from the SeaTalk1 bus (consider to use a fuse or a circuit braker if you are connecting the multiplexer directly from a battery). If you are using the SeaTalk1 bus you connect its 3 wires: 12V (normally red), GND (normally black) and DATA (normally yellow) to the screw connectors with labels 12V, GND and DATA. If you are not using the SeaTalk1 bus, you only use 12V and GND and will leave DATA unconnected. The 2 serial input ports, P1 and P2, have labels A1/B1 and A2/B2. Some instruments instead of A/B use Nmea+/Nmea- . In such a case you connect Nmea+ to A1 (or to A2) and Nmea- to B1 (or B2). If your Nmea data is available through a single ended port (such as RS-232) you connect its Output terminal to the multiplexer A1 (or A2) and its Ground (or common) terminal to the multiplexer B1 (or B2). The serial output port P3 uses the connectors labelled as A3/B3. There is a jumper that defines the state of B3. From factory this jumper sets B3 as GND and this works in 99% of the cases. If you want to configure P3 as a differential output port you need to relocate the jumper to the opposite side and be sure that you connect P3 to a differential (preferably an opto isolated) input port.


This multiplexer is totally WiFi configurable. When powered for the first time, it starts with factory settings and it will automatically create a WiFi network named NMEA3WiFi. You should disconnect your smartphone (or your PC) from other networks (if possible turning mobile data OFF) and connect to this NMEA3WiFi network using the password 12345678. When you are connected, type the address in the navigation bar of your browser and you will receive a web page which allows you to fully configure the multiplexer, and select modes of operation.


At any time, you can return to default factory settings by pressing and holding down the switch labelled BOOT or SW1 for two seconds. For support, please visit: and the forum dedicated to the NMEA3WiFi multiplexer. Note that TH, SMD or even KIT versions may exist in the future and can differ from the pictures shown in the front page of this manual.


This web page is the response you receive when you type in the navigation bar of your browser after you connect to the NMEA3WIFI network. Note that the page will not respond to the commands SET, HARD RESET and UPDATE as it is not running in the multiplexer. Please see the sections in this site that describe these functions.


The Nmea3Wifi multiplexer is available in 2 versions: TH (Through Hole) and SMD (Surface Mounting Devices). They have the same functionality and only differ in the manufacturing technology. There are small differences shown in the following pictures. One difference is position of the USB micro socket. Depending on the size of the male connector, you may be able to use, in the TH version, the USB cable with the box cover mounted. In the case of the SMD version, either you mount the multiplexer without the box cover or you make an hole on the box on the wall opposite to the entry of the wires.

Multiplexer Box TH Version SMD Version