Garmin / Seatalk interface

[SunCat]

I Have check most of the threads on this subject and found nothing that could help me, the one I tried did not seem to work, this is my case if some one can help me:
Garmin 545 chartplotter to Raymarine autopilot ST4000.
Garmin has two NEMA ports: Blue wire port 1 Tx (out) Brown wire Rx (in) / Grey wire port 2 Tx (out) Violet wire port 2 Rx (in) also Red wire is power (10-32 Vdc) Ground. Raymarine ST4000 has a NEMA port Blue wire (Data in -ve) and Red wire (Data in + ve).
I have tried every different combinations including changing communications protocol to no avail. Has anyone been successful doing this setup? I don't want to use a seatalk interface box if possible.
Thank you all.
Gene

 

[Jackdaw]

try:

Garmin BLUE (P1TX) to ST4000 RED (DataIn +)
Garmin (GROUND) to ST4000 BLUE (DataIn -)

Set Garmin Port 1 to NMEa Standard

 

[SunCat]

I am a little confused with the Garmin wires; Red wire is Power (10-32 Vdc) Ground and the Black wire is (Power and NMEA 0183), so which wire should I use for the ST4000 Blue (Data in)?

 

[Jackdaw]

I am a little confused with the Garmin wires; Red wire is Power (10-32 Vdc) Ground and the Black wire is (Power and NMEA 0183), so which wire should I use for the ST4000 Blue (Data in)?

BLACK/ground.

 

[Bill Roosa]

all data communications take 2 wires (at least) NMEA takes 2 wires, a signal and a ground.
Think of Tx and Rx as the same kind of "signal" and ground as something needed to show a difference between TX/Rx and 0 volts. (it is a floating ground BTW which is why you can't use the power ground).
so Transmit (Tx) goes to receive (Rx) and all the grounds get tied together.
also NMEA is a single talker and many listener circuit so if you want two devices to talk bi-directional you need 2 ports, a Tx on each and a Rx on each (Tx to Rx on both) and tie all the grounds together (except the power ground as that will introduce noise........can it get more complicated????)

 

[SunCat]

Garmin gray(P2TX) to ST4000 RED (DataIn +)
Black wire (Power and NMEA 0183) to ST4000 BLUE (DataIn -)
Set Garmin Port 2 to NMEA Standard
I had to use Port 2(Gray) because Port 1 (blue) already in use for DCS radio.
after the above mentioned setup St4000 still does not respond to chartplotter commands, anything I am still missing? Route to, Guide to or Go to do not work on St4000.
Gene

 

[Johann]

Under NMEA setup, try "Waypoint IDs" > "Numbers"

 

[Johann]

Sorry so vague, that's NMEA setup on the Garmin. I had the same issue with the ray x-5 wheelpilot and it was because the waypoint names sent from the chartplotter were too long.

 

[splax]

I am going to chime in, though I may not be much help.

The seatalk interface using NMEA is a daisychain series communication, with the autopilot passive and listening to all inputs to direct the steering
take the chartplotter out of the loop by connecting the wires (TX & RCV) from the NMEA interface to each other and verify everything else still works
check that chartplotter settings are those required by the autopilot
connect the seatalk interface wires to the chartplotter, I think the chartplotter is supposed to be the last instrument in the loop before the autopilot...
You should now be happy