I have a question about these 4 wires. Are they RS422 or RS232? I understand that NMEA0183 should be RS422, but it appears that sometimes it is not so.

I'm trying to interface these 4 wires to a serial port via a RS422 to Serial converter and its not working.

Thanks for your help!

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Raymarine NMEA 0183 ports are designed to the NMEA 0183 standard, which is essentially RS422.  The AIS500 is manufactured with a DE-9 serial plug to support interfacing the AIS500 with a PC for use with the ProAIS application or other PC application.  In doing so, the BAUD rate will be 38400.  One should not simultaneously interface the 38400 BAUD leads of the AIS500 to a product (ex. MFD) and use the aforementioned DE-9 serial interface, as the AIS500's 38400 BAUD leads are additionally connected to the leads of the DE-9 serial interface.

If using the AIS500's DE-9 serial plug to interface the AIS500 to your serial to USB adapter, then please note that the most cause for communications failures between a PC application and a NMEA 0183 device are

  • incorrect installation of the serial to USB adapter
  • inferior serial to USB adapter design
  • incorrect configuration of the PC application 

Raymarine and many other marine electronics and navigational software application manufacturers recommend or re-brand the SeaLevel Model 2105R and similar SeaLevel serial communications products for customers seeking a serial to USB adapter for use with their NMEA 0183 devices.  Communications between the AIS500 and PC may be tested using the ProAIS applications.  It should also be noted that a serial COM port cannot typically be shared be more than one application unless application software is installed on to PC to support COM port sharing (ex. GpsGate, etc.).

Thanks for that reply. I'm using a FTDIChip RS422 to USB serial converter...here is a description of the wires from the FTDIChip..

Colour Name Type Description
Black GND GND Device ground supply pin.
Brown CTS+ InputClear to Send Control + (B), Input
Red TXD- OutputData – (A) Output
Orange TXD+ OutputData + (B) Output
Yellow RXD+ InputData + (B) Input
Green RTS+ OutputRequest To Send Control + (B), Output
Blue RTS- OutputRequest To Send Control – (A), Output
White RXD- InputData – (A) Input
Grey CTS- InputClear to Send Control input – (A), Input

Which of these wires would I connect to?

Thanks for your help


I would recommend purchasing the serial to USB adapter recommended within my prior response and interfacing the adapter's DE-9 plug to the recommended adapter's socket.  Should you not elect to do so, then you may want to try interfacing the AIS500 to the serial to USB adapter as follows.

  • AIS500 38400 OUT+ to Adapter RXD+
  • AIS500 38400 OUT- to Adapter RXD-
  • AIS500 38400 IN+ to Adapter TXD+
  • AIS500 38400 IN- to Adapter TXD-

As Raymarine AIS receivers and transceivers feature a built in 38400 BAUD to 4800 BAUD multiplexer,

  • data received from an interfaced 4800 BAUD talker will be multiplexed with AIS data and the combined data stream will be transmitted by the AIS receiver/transceiver's 38400 BAUD output port (and corresponding pins of the DE-9 interface)
  • 38400 BAUD data received from a 38400 BAUD talker by the AIS receiver/transceiver's 38400 BAUD input port (and corresponding pins of the DE-9 interface) will be transmitted by the AIS receiver/transceiver's 4800 BAUD output port

As such, should the 4800 BAUD NMEA 0183 output from the E85001 PC/SeaTalk/NMEA 0183 Interface Module (which is interfaced to the SeaTalk bus featuring your ST60 Instruments) be interfaced to the AIS500's 4800 BAUD NMEA 0183 input leads, then the interfaced PC will receive a 38400 BAUD data stream including both AIS and instrument data.  Likewise, should your autopilot's 4800 BAUD NMEA 0183 v2.1 input port be interfaced to the AIS500's 4800 BAUD NMEA 0183 output leads, then 38400 BAUD NMEA 0183 sentences transmitted by the interfaced PC would be re-transmitted by the AIS500 to the autopilot at 4800 BAUD.

Thank you for the detailed very informative response! This is why I buy Raymarine products.

Thanks again

Best regards,


You're welcome.

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