SeaTalk, also known as SeaTalk1 to distinguish it from SeaTalkNG, is a proprietary bi-directional data interface developed by Raymarine for their marine products. SeaTalk carries marine data in a non standard serial format at relatively slow (4800 baud) speed. The segments of information that are transmitted through the SeaTalk bus are called datagrams and, in most cases, it is possible to convert those datagrams to equivalent Nmea 0183 sentences.
With the exception of N2K0183, all our multiplexers are capable of reading these SeaTalk datagrams and converting them to Nmea 0183 sentences. In addition, the Nmea3Wifi can also transmit SeaTalk datagrams, converting Nmea 0183 sentences into SeaTalk. To select a port to receive Seatalk on the Nmea2Wifi or Nmea4Wifi we need to choose SEATALK, instead of 4800 or 9600, in the relevant baud rate combo box. On the Nmea4Wifi, Port 4 (P4) can be switched to accept Seatalk. On the Nmea2Wifi, Port 1 (P1) is used for Seatalk. The Nmea3Wifi has a dedicated Seatalk port that does not need any selection.
| With the Nmea2Wifi and Nmea4Wifi multiplexers there are 2 options to power the multiplexers in a SeaTalk environment. In the picture below, on the left, we show an example of a Nmea4Wifi with power coming from the Seatalk bus. On a Nmea4Wifi, P4 is used (A4 and B4) to input SeaTalk data. (In the case of a Nmea2Wifi, Port P1 is used instead of P4). A second option (shown in the right hand photo) is to power the multiplexer directly from the main battery circuit. | In the case of the Nmea3Wifi wiring is simpler, as the multiplexer has only one power input, and this 12V connection can be connected to the SeaTalk bus 12V wire, or to the main boat instrument 12V power. The SeaTalk input is clearly marked. | |
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The following table on the left shows the conversions from Seatalk Datagrams to NMEA 0183 sentences in all the multiplexers that support SeaTalk.
Seatalk IN |
Nmea0183 |
About "$STALK" in Nmea3Wifi |
| 00 | $SDDBT |
In addition to the conversions shown on the left for "KNOWN" datagrams, the NMEA3WiFi multiplexer can convert Seatalk datagrams to the sentence "$STALK". This message allows raw Seatalk data to be sent over NMEA without interpretation in the multiplexer. It allows for application developers to use Seatalk datagrams that are otherwise not translated to NMEA sentences. For example, the Autopilot datagram "84" will normally generate the NMEA \HDG/HDM sentence regarding heading data. But in addition, in Seatalk mode 1 it will also generate a raw $STALK sentence, allowing applications to determine what state the autopilot is in and other data. The NMEA3WiFi multiplexer has four "levels" of $STALK capability.
TRANSMITTING $STALKBecause the NMEA3WiFI is completely bi-directional, it can accept NMEA $STALK sentences and send them out as Seatalk Datagrams. This allows application programs to -for example- simulate a Seatalk remote keypad. |
| 10 | part of $WIMWV | |
| 11 | $WIMWV | |
| 20 | $WIMWV | |
| 21 | $IIVLW | |
| 22 | $IIVLW | |
| 23 | $IIMTW | |
| 25 | $IIVLW | |
| 26 | $VWVHW | |
| 27 | $IIMTW | |
| 50 | part of $GPRMC | |
| 51 | part of $GPRMC | |
| 52 | part of $GPRMC | |
| 53 | $GPRMC | |
| 54 | part of $GPRMC | |
| 56 | part of $GPRMC | |
| 58 | part of $GPRMC | |
| 99 | part of $GPRMC | |
| 84 | $GPHDG or $GPHDM | |
| 89 | $GPHDG or $GPHDM | |
| 9C | $GPHDG or $GPHDM |
Conversion from SeaTalk datagrams to Nmea0183 sentences to SeaTalk datagrams in the Nmea3Wifi multiplexer
| SeaTalk In | NMEA | Seatalk Out | ||
| Seatalk IN | Debug Comment | NMEA | Comments | Seatalk OUT |
| 00 | Depth below transducer x.xxFeet | DBT | note: NMEA inputs do not trigger "debug comments" | 00 |
| DPT | ||||
| AAM | A2 | |||
| 10 | App Wind Angle stored | |||
| 11 | Wind speed (+ uses data from 10) | MWV | 10, 11 | |
| 20 | Speed through water | VHW | 20 | |
| 21 | Trip Mileage xxxx.xx | VLW | ||
| 22 | Total Mileage xxxx.xx | VLW | ||
| 23 | Temp (x C), (x F) | MTW | 27 | |
| 25 | Total & Trip Log | VLW | ||
| 26 | STW x.xx Kts(or mph) | VHW | 20 | |
| 27 | Water temperature x.x deg C | MTW | 27 | |
| GLL | 50,51 and 54 | |||
| VTG | 52 , 53 | |||
| 50 | Lat Degrees stored | Note RMC will trigger multiple Seatalk datagrams: | ||
| 51 | Long Degrees stored | |||
| 52 | GPS SOG stored | |||
| 53 | COG + Uses data from 50,51,52,54,56 /58 and 99 | RMC | 0 | |
| 54 | GPS Time stored | (* only sent if SOG_to_STW is set AND Seatalk#20 (STW) has NOT been seen | ||
| 56 | GPS date stored | |||
| 58 | GPS data (full) stored | |||
| 99 | Mag Var stored | |||
| 84 | Autopilot data incl Heading | HDG or HDM (+ $STALK- see NOTE 1) | 89,99 | |
| 89 | HDG or HDM depends if Mag Var is available | HDG or HDM | HDM > 89 (only) | |
| 9C | Compass heading and Rudder position | HDG or HDM | HDG > 89 + 99 | |
| 9E | Waypoint definition | (not currently converted) | ||
| WPL | Routing sentences get converted to Seatalk 85 and A1. Waypoint names are limited to 8 characters. | |||
| XTE | ||||
| APB | ||||
| RMB | ||||
| BWR | ||||
| BWC | ||||
| BOD | ||||
| 85 | Navigation to waypoint information (not currently converted) | |||
| (When selected by ST Group mode) eg $STALK,… | ALK | (whatever is in $STALK…) | ||
| Alternate Transliteration command: $PSMDST | MDS | (whatever is in $PSMDST…) | ||
| Raymarine performance feedback Eg $PTAK,FFD3… | AK | (ignored) | ||
| (1) Note. With NMEA3, it is possible for aplications to generate $STALK messages to send data over SeaTalk that otherwise has no NMEA equivalent. This is useful for example with ST84, which can then send autopilot status as well as Heading data to suitable apps. | ||||