About 15-year ago in 2011, I was very interested in the new marine service of the Automatic Information System or AIS. At the time there were very few AIS receivers available, but a relatively new product from em-trak was the $220 R100 AIS receiver. The R100 supported the dual-channel AIS transmission protocol. em-track is the house brand for SRT Marine Technology, which was then and is now the very well established leader in AIS technology.
I used the em-track AIS R100 receiver as part of my mobile AIS receiving station, and wrote about my adventures in initial reception of AIS signals, which at that time were primarily being sent from larger commercial ships. My house was too far from navigable water with ship traffic, so I had to create a mobile AIS receiver, GPS receiver, computer, and chat plotter. A December 2011 article explained the details. See
- AIS Ship Spotting
https://continuouswave.com/whaler/refer ... otter.html
At that time I was using the micro-USB port on the R100 to connect the data output of the receiver to my MacOS laptop computer. The "road warrior" setting put must have put too much strain on the micro-USB connector, and eventually mechanical problems with the connector caused intermittent connections.
Over time, manufacturers of VHF Marine Band DSC radios began to offer models that included an internal AIS receiver, which for shipboard use was clearly a better option than using the R100. The advantage of the DSC radio with AIS receiver was a separate antenna for the AIS receiver (as needed for the R100) was not necessary; the integrated AIS receiver would just share the DSC radio antenna.
Just recently, I dug out my R100 AIS receiver with the damaged USB-micro port and experimented with using its PWR/DATA port to get to the NMEA-0183 AIS data output. Herein I will give some details about using the NMEA-0183 wired signal from the R100 to interface with a computer. The computer in this case is the Apple Mac Mini M4 model, and the chart plotter application that will display the AIS data is OpenCPN.
R100 PWR/DATA Cable and Connectors
The R100 has a 12-pole connector and mating 12-conductor cable assembly that allows use without needing the micro-USB output. The engineers must have had some other features in mind, as six of the twelve conductors in the cable are designated "not used." As typical, the cable terminated in loose individual conductors, all with unique wire insulation colors. The active circuits are as follows:
RED = Power in +
BLACK = Power in -
BROWN = Transmit + (TALKER A)
BLUE = Transmit - (TALKER B)
GREEN = Receive - (LISTENER B)
WHITE = Receive + (LISTENER A)
Note that the wire color coding from the R100 is NOT the recommended wire color code for NMEA-1083. This often occurs as manufacturers may not be able to source the particular wire colors recommended or designed their product before the NMEA organization published their standard wire colors. The now standard NMEA wire color coding is show below.
TALKER A = WHITE
TALKER B = BROWN
LISTENER B = GREEN
LISTENER A = YELLOW
Also somewhat ironically the R100 apparently does not respond to any input commands via the NMEA-0183 interface. I was hoping that perhaps the receiver provided some ability to accept input commands and produce some status output, such as the signal strength of the received AIS signals or an ability to set the baud rate. I suspect there might be such commands and corresponding output signals, but em-trak has not disclosed any. As a result, there is no purpose to having the R100 include LISTENER A and LISTENER B signals.
To terminate all of these loose wires into connectors, I relied on two standard conventions. For the 12-Volt power I used Anderson Power Pole connectors in red and black bodies with 15-Ampere contacts. However, these can be assembled in several ways, but I settled on a de facto standard in the Amateur Radio community, known as the Orange County RACES Power Pole standard.
RACES is an acronym for the Radio Amateur Civil Emergency Service. Apparently Orange County, California was the trend setter, and their configuration of the Powerpole connector became the standard.
For the NMEA-0183 connector, I used my own standard, nylon 0.100-inch header connector. (More details on the connector below).
The stock em-trak Power/Data cable with connectors added is seen in Figure 1 below:
Fig. 1. The Power/Data cable for the em-trak R100 AIS receiver with connectors added for my application. The power conductors in the Power/Data cable are extended by a length of gray cable with red-black conductors to the Anderson Power Pole plug assembly for connection to a 12-Volt power supply.
Details of the wiring of the five-position nylon header connector
The five-position header connector is Molex nylon 0.100-spacing friction-fit header connector which will mate with five-pin headers on the "universal" NMEA-1083 interface motherboard header cross-connection system that I designed. The standard connector layout is thus:
TALKER A
TALKER B
POWER COMMON
LISTENER B
LISTENER A
The connector body does not have position identifiers, but my standard is for the connector body to be oriented with the top and bottom edge extensions oriented to the right with the body oriented vertically and viewed from the back of the connector. All my NMEA-018 devices are wired in this way, no matter if they are balanced or unbalanced signals. When two NMEA-0183 devices using my standard connector and signal layout are connected to my motherboard with pin headers, the cross connecting of TALKER to LISTENER occurs via the wiring of backplane of the motherboard. On the motherboard with the header pins, the polarization of the headers is flipped for each pair set, so when the pins are wired straight across via the motherboard, the orientation of the connector flips, which creates the necessary cross connection of the signals.
The header connector details are as follows:
Connector Body
- Molex 22-01-3057;
- Headers & Wire Housings KK 254 Crimp Housing, Friction Ramp w/ Polarizing Ribs, 5 Pos., Natural
- Molex 08-55-0102
- Headers & Wire Housings KK 254 Crimp Terminal, Female, 30-22 AWG, 0.38 m Selective Gold (Au) Mating Pltg, Nickel Term. Pltg, Brass, Bag
The wiring of the R100 to the five-pole connector for the Universal NMEA backplane crossover is shown in Figure 2 below:
- Fig. 2. Wiring R100 to NMEA interface five-pole connector according to my own standard, as explained above.
- NMEAbalancedWiring.jpeg (86.78 KiB) Viewed 677 times
The NMEA-0183 Cross-connect Motherboard
Figure 2 below shows my design for the NMEA-0183 cross-connect motherboard. The five-position pin headers are mounted in pairs, with the connector friction retainer orientation swapped on opposing sides. The header pin assembly detail is as follows:
- Molex 22-11-2052;
- Headers & Wire Housings KK 254 Solid Header, Vert., w/ Friction Lock, 5 Pos., 0.51 m Gold (Au) Pltg, 3.56mm Tail Lg., Bag
The circuit board that was used to construct the motherboard as seen in Figure 2 was from Radio Shack. In 2026 that particular circuit board is no longer available. I am looking for a substitute circuit board from currently available stock printed circuit breadboards that is particularly suited for making the cross-connect motherboard for NMEA-0183.
As seen in Figure 2, the connected device on the right is a NMEA-0183 balanced signal from the R100. On the left side is an RS-232 circuit from a USB-to-RS232 Serial Adaptor. The wiring of the cable also provides a circuit from the expected LISTENER B to the Power Common (middle conductor).
- Fig. 3. A universal NMEA-0183 motherboard or backplane with paired 5-pole connectors. The R100 is providing (A/B) balanced NMEA-0183 TALKER and LISTENER signals on the left side, and on the right side a special interface cable is carrying the signals to an RS-232 to USB serial adaptor via DB9 connectors.
- NMEA-0183Motherboard.jpg (51.87 KiB) Viewed 1262 times
The TALKER A output of the R100 is on the brown conductor, which is then connected to the RS-232 RX-data input on the red conductor. The TALKER B output of the R100 is on the blue conductor and is not connected to anything, so it just floats.
The LISTENER A input of the R100 is on the white conductor (lower), which is then connected to the RS-232 TX-data output on the black conductor in the special cable.
The LISTENER B input of the R100 is on the green conductor, which is then connected via the wiring in backplane to the connector from the other device; that connector includes a jumper from the power common common of the other device to the pin where the TALKER B circuit is expected. In this way LISTENER B in the balanced device is connected to the power common in the unbalanced device actual wired connection that is provide in the special cable; this connection creates a path for the LISTENER B (which is from the other device which is assume to be using balanced NMEA-0183) to be connected to the common or ground (shield) of the RS-232 circuit (which in this case is the RS-232 port on the RS-232 to USB adaptor). This is another feature of my universal interface: one side can be a balanced NMEA device and the opposite side can be a single-ended NMEA-0183 device (or an RS-232 interface to a computer).
Special Cable RS-232 to NMEA-0183
The special cable for RS-232 on a DB9F connector to my standard 5-position header connect for NMEA-0183 is shown in Figure 2.
- Fig. 4. Special cable assembly: RS-232 DB9F to 5-pole NMEA Crossconnect header.
- specialCableDB9Fto5PoleHeaderConnector.jpg (78.1 KiB) Viewed 1768 times
The NMEA Cross-connect end of the special cable wiring is shown in Figure 4.
- Fig. 5. Detail of the wiring at the RS-232 connector.
- unBalancedNMEA-0183Con.jpg (57.05 KiB) Viewed 1258 times
The other end of the special cable terminates in a DB9F connector, with the wiring as follows and illustrated in Figure 5:
- Fig. 6. DB9F wiring detail.
- DB9-F_Wiring.jpeg (59.22 KiB) Viewed 1768 times
PIN 1 DCD = Jumper to PIN 4 DTR
PIN 2 Rx Data = RED
PIN 3 Tx Data = BLACK
PIN 4 DTR = Jumper to PIN 1 DCD
PIN 5 GND = cable SHIELD conductor
As mentioned above, in the case of connecting the em-trak R100 AIS receiver, there is no particular need to allow the RS-232 device to send data to the R100 serial port input, but this was incorporated into the cable anyway. In this manner the cable is essentially a universal cable for connecting an RS-232 device to the NMEA-0183 cross-connect motherboard.
This completes the detailed explanation of the wiring and interface between the R100 wired NMEA-0183 output signals and the USB connection to the host computer that will be running the OpenCPN chartplotter application.