Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 03-07-2010, 21:35   #1
GWB
Registered User

Join Date: Sep 2008
Location: Brookings, Oregon
Boat: Westsail 32
Posts: 296
Images: 1
Com Port Ground

I just connected up my laptop to the output of my Furuno GP36 so as to receive nav data from the Furuno and run Seaclear on the laptop. It works fantastic for a while and then starts producing Egyptian hieroglyphics (I can look at the input using hyperterminal) I verified that it is not the output from the Furuno by checking the GPS data on my vhf (this recieves the same input from the Furuno)

Sooo, the problem is either noise (and I turned off everything around it - makes no difference) or its some kind of ground/common problem. The common/ground is connected to pin 5 on the pc com port... and the only other wires connected to the com port are tx and rx.

Anyone else experienced this kind of problem?

Thanks for any input
__________________

__________________
GWB is offline   Reply With Quote
Old 04-07-2010, 00:51   #2
Registered User
 
SariTimur's Avatar

Join Date: Oct 2008
Location: Seward, Alaska
Boat: William Garden Ketch
Posts: 170
I have had this with some other high speed nav data on computers where the RS232 ground alone was not good enough. I was told by the supplier of that equipment to connect the shield to a ground on the computer. They suggested the screw that connects to the DB9 connector on the computer side. When I did this it worked. Once we started using laptops with USB to DB9 connectors problem didn't exist so I guess there the ground was looped through already or the newer laptops were better against noise. Never found out but it would be worth trying in you case not to hard to give it a whirl. It is interesting though that hyperterminal doesn't see a problem.

Cheers
__________________

__________________
SariTimur is offline   Reply With Quote
Old 04-07-2010, 02:08   #3
Registered User
 
richardhula's Avatar

Join Date: Nov 2008
Location: UK
Boat: S M Hudson 60' narrowboat
Posts: 347
Send a message via Skype™ to richardhula
Try strapping the -ve signal lead (pin 5 on db9) to battery negative/ground. This is the most common solution for such problems giving the +ve signal a firm reference.

Probably easiest to do this where lead joins Furuno GPS.
__________________
Richard

If in doubt RTFM
richardhula is offline   Reply With Quote
Old 04-07-2010, 20:38   #4
GWB
Registered User

Join Date: Sep 2008
Location: Brookings, Oregon
Boat: Westsail 32
Posts: 296
Images: 1
Thanks - I'll give it a whirl Richard. Sari - I did try tying ground/batt negative to the computer case and that did not work. Hyperterminal is the device showing the weird characters... sometimes. Other times the characters are as they should be - that is strings of english characters and numbers
__________________
GWB is offline   Reply With Quote
Old 05-07-2010, 20:13   #5
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
There is "freeware" that will display the output of your GPS on your computer - VisualGPS™
This is a good way to confirm that the GPS output is really getting into the computer. You can open the programs NMEA sentence window and watch the actual GPS sentences being downloaded to your computer. It also has current position and accuracy windows plus more to see how the GPS if performing.
- - With any new installation of a computer navigation program I also install the Visual GPS program to be sure that the GPS is "talking" to the computer before trying to "install/activate" the GPS in the navigation program.
- - One limitation is that you can only utilize one program that will be using the GPS at a time. You cannot run the navigation program and a GPS utility program at the same time - at least not on any computer I have used.
- - There is an old time problem that affects Windows operating systems and GPS's - and that is that the operating system can think that the GPS signal is a "mouse" signal and it causes strange things to happen especially with the cursor. The work-around was to start the computer without the GPS turned on or plugged in and also the navigation program - and then turn on or plug in the GPS to the computer. It was also common that once the navigation program was shut down that other programs with "comm" port provisions would go weird if the GPS was still turned on.
__________________
osirissail is offline   Reply With Quote
Old 06-07-2010, 03:13   #6
Registered User
 
richardhula's Avatar

Join Date: Nov 2008
Location: UK
Boat: S M Hudson 60' narrowboat
Posts: 347
Send a message via Skype™ to richardhula
Quote:
Originally Posted by osirissail View Post
One limitation is that you can only utilize one program that will be using the GPS at a time. You cannot run the navigation program and a GPS utility program at the same time - at least not on any computer I have used.
By itself true, but there are many utility programs available that will echo or distribute the GPS signal on your PC to several of other programs simultaneously via virtual COM ports.

Google NavMonPC (free) or GpsGate.
__________________
Richard

If in doubt RTFM
richardhula is offline   Reply With Quote
Old 10-07-2010, 04:48   #7
Registered User

Join Date: Feb 2008
Posts: 2,060
Pin 1 is for chassis ground. Pin 5 is signal ground (in a DB-9 connector). Generally no harm if you tie them together.
__________________
SailFastTri is offline   Reply With Quote
Old 10-07-2010, 05:16   #8
Registered User

Join Date: Feb 2008
Posts: 2,060
Quote:
Originally Posted by richardhula View Post
Try strapping the -ve signal lead (pin 5 on db9) to battery negative/ground. This is the most common solution for such problems giving the +ve signal a firm reference.

Probably easiest to do this where lead joins Furuno GPS.
GPS will generally use Pins 2 (transmit), 3 (receive)and ground (pins 5 and 1) on a db9 connector.

The serial port on the PC should be set for 8, N, 1 (8 bits, no parity, 1 stop bit) and data rate matters. The issue in the original question could be caused by mismatched data rate.
__________________

__________________
SailFastTri is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Assign USB Port to COM Port ? GWB Navigation 10 17-05-2010 19:27
AC Ground redcobra Electrical: Batteries, Generators & Solar 1 23-05-2009 15:54
Military port? Civilian port? Amgine Indian Ocean & Red Sea 1 21-09-2007 10:37
SSB Ground phorvati General Sailing Forum 2 03-04-2006 12:12
ssb ground davemaskell Marine Electronics 17 02-12-2005 19:47



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:41.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.