SeaTalk is a simple networking interface used by Raymarine to link their range of marine equipment together so that data can be shared across all devices. Technology wise it is best described by SeaTalk Technical Reference.
The hardware project here is designed to read SeaTalk data and convert it to standard NMEA data. Such devices are available commercially but can be very expensive. The one manufactured by Digital YACHT is sold for £150 whereas the solution here can built for £10 - £20.
The proposed solution is based around the Arduino Pro Micro. This device was chosen as it provided two hardware serial ports. One port is accessed via the USB connection and the second is available on the board. The intention being to read the SeaTalk data via the on board serial port and make the NMEA data available via the USB.
SeaTalk is a serial interface that uses a 12 volt signal line. To interface this to the Arduino it must be converted to TTL level, this can be done using the circuit published by Berreizeta:
This can easily be built on Veroboard and the whole device assembled as:
The Arduino is programmed via the USB connection and when connected to a SeaTalk device can produce sentences such as:
$PIMSST1,D,20,41,0,0*5e $GPVHW,,,,,0.0,N,0.0,K,*77 $PIMSST1,D,0,42,64,0,0*41 $GPDBT,0.0,f,0.0,M,0.0,F*06 $GPDPT,0.0,0*49
The NMEA sentences starting $P are proprietary sentences that show the actual SeaTalk data being processed. These are used for debugging purposes and can easily be turned off.
For further information about the software please contact me via the Contact page.