Wiring Help: GP-31 > FCV-620



I'm trying to get my GP-31 to talk to my FCV-620. I guess I just don't understand the wiring diagrams in the manuals. Can anybody tell me the proper way to hook these two up?

If I follow what looks like should be in the manual?, it doesn't work:
TD-H (White)---------->RD-H (Rd-A?) - Yellow
TD-C/SG (Blue)--------->RD-C (Rd-B?) - Green

But if I hook up the following, seems they somewhat talk (at least GPS lat/long displays on the 620):
RD (green)------------>RD-B (green)
SD (yellow)------------>RD-A (Yellow)

Forgive my ignorance in the matter ... I just can't see me embarking on my next project (GP-31 to PC) if I can't even get this simple one right! :questions
Here is the decoder ring for reading the Furuno interconnection diagram at the back of the manual (pg S-1).

TD = Transmit Data
RD = Receive Data
A = +
B = -
H = Hot/High/+
C = Cold/Common/-
SD = Send Data
SG = Signal ground

The first example you provided would be correct and should work. Are you sure the wire colors you are looking at, is from the original Furuno power/data cable of the GP31? If someone extended the cable they might have changed the color code of the wiring. The second example you provided would be intermittent at best, because you are using a RS232 NMEA port to drive into the FCV620 RS422 NMEA port. (NMEA level mismatch) It could be that your NMEA data 1 port of your GP31 is damaged/broken. In that case you would either need to get it repaired, or use port 2 with a proper level converter as an interface. (RS232 to RS422 converter)
1) Thanks so much for the reply & info. No wiring color issues, GP-31 cable is actually brand new. I took apart both the GPS and 620 and traced both power/data cables from plug end to where they mate with the controller boards, all seems good. So if my first wiring example was correct then as you said seems must be a problem with the GP31 data1 port, or perhaps even the 620 internals?

2) Not the end of the world for me as my main goal is to have the GPS feed both sounder and PC, .... (pc using either memory map, ozi explorer, fugawi, etc), until I can afford a Furuno all-in-one. I can live with the 620 not talking correctly to the GP-31 if it ends up costing too much to fix.

I was able to get RS232 from the GP-31 talking to the PC via a USB RS-232 converter (4800,n,8,1), but can you tell me if this is the correct RS232 wiring for GP-31 > PC? (I think I'm following the manual diagram correctly). Currently PC can read GPS position info but can't seem to transfer waypoints/routes back & forth with this setup:

Yellow (SD)------------------->Brown(Pin2 RD)
Blue (TD-C)------------------->Yellow(Pin5 SG)
Green (RD)------------------->Red(Pin3 TD)
White--------------------------> nothing
--------------------------------> purple-blue (pin8 CTS - pin7 RTS) tied together
--------------------------------> orange-green (pin4 DTR - pin6 DSR) tied together
--------------------------------> white (RI - no conn)
--------------------------------> black (DCD no conn)

Thanks again for any help, this forum helps a ton, glad you all created it. :furuno
Since your FCV620 was able to get some info when you had the NMEA mismatch connection; I would have to say the NMEA input on that unit is fine. Your problem would be with the older GP31 unit. You must be very careful when matching NMEA 0183 because there is not only the version to consider, but also the level (Like RS232 and RS422). If you wish to feed both a RS232 (PC) and RS422 (Sounder) device from a RS232 port, you would require an interface. A common one used is the Noland Engineering XP15 (NMEA EXPANDER). It will accept the NMEA 0183 (Either RS422 or RS232) and provide 4 each RS422 outputs and one RS232 output from one NMEA talker. This might be a good solution for you.

Your example of driving your GP31 data 2 to the PC is PERFECT :jump

We are very glad to have you as a part of the Forum. Thanks for the supportive comments.
Since you mentioned NMEA version I played with some settings. Found that if I set both GP-31 & FCV-620 to NMEA v1.5 (instead of 2.0 which is what they were), 620 now gets GPS data via the original Data1 wiring setup. :) Sooo, I guess maybe Data1 on GP31 not bad after all since now pumping data over TD-H & TD-C. Doesn't make sense to me why on v2.0 they wouldn't work, but heck it's working on v1.5 so I'll just leave it.

PC is still talking via RS232 to GP31 Data2, so I'm looking pretty good now (all 3 getting most of what they need). Still can't get waypoints/routes to xfer between GP31 and PC (to or from). Pretty sure all com port settings are correct, but still no-go. But I guess I can live with that for now as I plan to use the laptop for most nav anyway... and it's getting the data I need. May revisit that part later... time to install everything in the boat and go catch some fish :cool

Thanks again!