Advice to connect GPS and pilot sought

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island
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Re: Advice to connect GPS and pilot sought

Post by island »

My apologies to all

For some unknown reason I referred to a GPS as a modem.

I am using a usb GPS.

Thanks :oops:
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

Makes sense now!
Even so, in my experience USB/serial converters don't necessarily work well in every situation. It's so problematic that serial ports are available on laptops once again. My current laptop has one because in the automation field we regularly use RS232 comms.
Cheers,

Neil

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Re: Advice to connect GPS and pilot sought

Post by zebedee »

Tymadman wrote:Island is using a USB port via a hub (I assume - island called it a 'modem') connected to a USB/serial converter.

This arrangement is likely to result in reduced signal levels compared to a direct connection to a serial port, unless the hub is externally powered.

If the laptop is not transmitting any NMEA data then yes, that's the first thing to fix of course.
The USB GPS isn't talking to the serial port, it talks to the software in the laptop which generates the NMEA signal out via USB and the USB to serial adapter.

I've not had any problems connection a GPS on a serial cable to a USB/serial converter. The voltages from the USB/serial converter were adequate to send instructions and data to the GPS. On that basis, the tillerpilot should also be able to read the data from the USB/serial converter.
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

zebedee wrote: but where is the GPS in this set up?
island wrote:The GPS is plugged in to the laptop via a usb port.
Thanks, I expected this would be the case, but I wanted to make absolutely sure.
island wrote:The GPS supplies data to the OpenCPN navigation software.
The OpenCPN navigation software has many functions including:

-- Route navigation.
-- Waypoint navigation.
-- NMEA 0183 GPS interface at selectable baud rate.
-- Autopilot output support.
Good, ok, assuming signal levels etc all work for you, the issue now is cabling?

There are a couple of ways you could go here:
  • Fit a lead with female DE9 socket on the end to the boat (and so to the tillerpilot). Make it long enough to reach your laptop serial port. Optionally, also fit a convenient 2 pin plug between the lead and the boat so you don't have a dangling cable.
  • Fit a male DE9 serial plug to the boat. Use a null modem cable to connect it to the laptop. The advantage is that this would allow you to plug any convenient GPS with a serial cable in place of the laptop. The disadvantage is that null modem cables are getting hard to find.
If you go for the first option, you can also make up a spare lead with the same 2 pin plug if you do later decide to use an alternative GPS source.

Let us know which you prefer, then I'll look up the pinouts to check you've got the wires going the right places.

Given the potential for mistakes, it would be good if someone else (Tymadman?) does this too!
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

PS, just to be sure we're all on the same page here,

These are male DE9 connectors:
On a lead
Image

On a panel
Image

These are female DE9 connectors:
On a panel
Image

On a lead
Image

BTW, that last image is of a null modem cable.
All that is special in a null modem cable is that the "send" pin on each end is connected to the "receive" pin at the other end, otherwise neither device would ever receive what the other sent!
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

I'm happy to help. They're called DB9 connectors BTW Zeb.
Jaycar still sell null modem cables. You can also get this style which I prefer...
Image
Cheers,

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Re: Advice to connect GPS and pilot sought

Post by zebedee »

Tymadman wrote:I'm happy to help. They're called DB9 connectors BTW Zeb.
That's how I remembered it too, but it seems the correct name is in fact DE9.
http://en.wikipedia.org/wiki/DE-9_connector
Tymadman wrote:Jaycar still sell null modem cables. You can also get this style which I prefer...
Image
I'd forgotten about those, which would make option 1, fitting a female DE9/DB9 on a lead, more sensible, as long as we don't end up crossing over twice or something. My brain hurts.
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Re: Advice to connect GPS and pilot sought

Post by island »

zebedee wrote:
There are a couple of ways you could go here:

[*]Fit a lead with female DE9 socket on the end to the boat (and so to the tillerpilot).

That's exactly what I have been trying to achieve as I attempted to show in my photo.
The component with the green (2), white (3) & black (5) wires is a female DB9 socket which I have wired up for the tiller pilot.

I have tried every combination of connecting those wires to pins 5 & 6 of the tiller pilot.

Image


This is a closer look at the front & back of the female DB9 Serial socket

Image

Image
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Re: Advice to connect GPS and pilot sought

Post by mob »

zebedee wrote:

Image
Wow, same sex cabling.
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

First of all, setting up the USB to serial adapter can be fiddly to say the least. Is your software seeing the serial port? Do you have anything you can use to test it, even just a serial mouse?

Assuming you've got the serial port working (big step!)...
island wrote:The component with the green (2), white (3) & black (5) wires is a female DB9 socket which I have wired up for the tiller pilot.

I have tried every combination of connecting those wires to pins 5 & 6 of the tiller pilot.

Image


This is a closer look at the front & back of the female DB9 Serial socket

Image

Image
OK, here's what the pinouts are supposed to be:
Image

You need pin 5 (data ground) and ping 3 (transmit data from the laptop)

Pin 5 (your black wire) goes to pin 5 (NMEA-) of the tillerpilot socket
Pin 3 (your white wire) goes to pin 6 (NMEA+) of the tillerpilot socket

Image

Pin 4 from the laptop goes nowhere because there is no data coming back from the tillerpilot.
Obviously you also need to provide 12V to the tillerpilot on pins 1 (+12V) and pin 2 (0V) of the tillerpilot socket. Less obviously, NMEA- may be grounded to 0V elsewhere in the system.

If you've got the wiring correct as above, I'd suspect the serial port isn't configured right. And yes, it's a pain to figure out.

Tymadman, could you check me for mistakes please?
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

If anyone was curious, here's a diagram showing what's going on in a null modem cable or adapter:

Image

What one side sends, the other side receives, and vice versa.
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Re: Advice to connect GPS and pilot sought

Post by porridgepots »

The other critical thing is your serial port settings on your software
Should be set to 9600 baud, but you can try 4800 if you are getting no response from open cpn
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

For a direct connection (no null modem)...

Pin 3 of the laptop serial port needs to connect to pin 6 at the tiller pilot.

Pin 5 of the laptop serial port needs to connect to pin 5 at the tiller pilot. (or connect pin 5 at the tiller pilot to any 0V as Zeb pointed out).

If using the null modem , connect pin 2 instead of pin 3 at the DB9 connector.
The other connections stay the same.

Hopefully that should work.

By 'laptop serial port' I mean the DB9 connector that you are connecting to the USB/serial converter at the laptop.
Cheers,

Neil

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Re: Advice to connect GPS and pilot sought

Post by island »

Thanks for your suggestions gentlemen.

I've tried them all, yet I'm no closer to resolving this enigma.

As far as I can tell (according to my laptops device manager) my USB to serial socket is installed correctly. OpenCPN can see it & designates it a COM port. My USB GPS is working fine & OpenCPN also designates it a separate COM port

I have tried the following (on 2 separate computers) with no success:

- Connecting Pin 3 of the laptop serial port to pin 6 of the tiller pilot,
& Pin 5 of the laptop serial port to pin 5 of the tiller pilot.

I have also adjusted the GPS, Serial & OpenCPN Baud rates to 4800 & 9600.

As far as I'm aware my tiller pilot should indicate bearing & distance to way-point ( from OpenCPN data) after I press & hold -10 & +10 buttons for a few seconds. All the tiller pilot will display is it's usual fluxgate compass heading.

Any other suggestions?

P.S. Here is a photo of the settings.

To the left of red line = OpenCPN settings
To the right of red line = My laptop device manager settings.
(Prolific usb-to-serial com9 is my GPS)

Image
Last edited by island on Jul 19th, '12, 16:19, edited 2 times in total.
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Re: Advice to connect GPS and pilot sought

Post by porridgepots »

porridgepots wrote:The other critical thing is your serial port settings on your software
Should be set to 9600 baud, but you can try 4800 if you are getting no response from open cpn
Further to above, it looks like NMEA is only 4800 with 8 bits & one stop bit - no parity ( source: http://en.wikipedia.org/wiki/NMEA_0183 )
if you don't have these settings in your connection configuration in your software you will not get anywhere
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

Do you have a handheld GPS and serial cable?

This would allow you to do two tests
- see if the software can find the GPS on the serial port adapter
- make sure the tillerpilot is not faulty and will respond correctly to NMEA input (You'll need to make a lead with a male DE9 for this test)
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

island, it could be your USB/serial converter. These are very problematic. If you have two different ones, one will work fine on some things but the other won't work on the same things, and vice versa.
See if you can borrow a different make of converter.
Cheers,

Neil

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Re: Advice to connect GPS and pilot sought

Post by island »

I don't have any other GPS or Serial equipment at my disposal.

I have however just been experimenting crudely with a multimeter.

With everything connected as mentioned in my last post, I put the multimeter probes on pin 3 pin 5 of the serial out puts (which provide the NMEA data to tiller pilot).

There was a steady reading. But as soon as I activate a route in OpenCPN the volt meter reading jumps all over the place & when I deactivate the route the volt meter reading remains steady again.

I therefore presume (a wild guess) that there is in fact data being sent to the tiller pilot.

Perhaps the tiller pilot is at fault although it is just a few months old.
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

What signs are you looking for at the tiller pilot that it is receiving data? Is it in the correct mode?
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Neil

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Re: Advice to connect GPS and pilot sought

Post by island »

Hi Tymadman,

As far as I'm aware my tiller pilot should at least indicate bearing & distance to way-point data from OpenCPN

In the ST2000+ Tiller pilot manual I think the relevant mode is referred to as Track mode (page 14 section 2.4)

To put the tiller pilot in this mode the manual states to press auto & then hold -10 & +10 buttons for a few seconds. I've also tried holding down the - 1 & + 1 buttons together & without pre-pressing auto.
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

That sounds right.
Cheers,

Neil

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Re: Advice to connect GPS and pilot sought

Post by island »

BINGO!

I've finally got it to work!

The tiller pilot is for the first time displaying the track heading, distance & bearing to waypoint data from the laptop's OpenCPN software.

I'm not exactly sure why it didn't work earlier.
It appears that I had the correct wiring & OPenCPN settings from the start.


It may have been as simple as holding the Tiller pilots -10 & +10 buttons down for too long when trying to enter Track mode.
They just need to be pressed for a fraction of a second.

There could also have been an issue with the Tiller Pilot's orientation & the route I created on OpenCPN in order to test the equipment.
If I find out anything revealing I'll post back again.

Hopefully I can recreate my bench test next time I'm afloat!
I'll let you know how it goes.

Thanks for the assistance.
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Re: Advice to connect GPS and pilot sought

Post by Tymadman »

Congrats island! We weren't any help at all it seems :-)
Cheers,

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Re: Advice to connect GPS and pilot sought

Post by island »

Au contraire my dear fellow,

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth"

I'm sure I would have given up my quest for connectivity had it not been for the generous support & insightful contributions of members.
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Re: Advice to connect GPS and pilot sought

Post by zebedee »

island wrote:Au contraire my dear fellow,

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth"
That's usually about when I discover that there are further possibilities that I'd never even considered!

A bit like the tale of the missing gas bottle recounted here recently:
Gas company delivers new 2nd bottle to replace empty
TSP member finishes current bottle and swaps to newly delivered 2nd bottle.
Second bottle empty!!
Gas company insists they delivered a new bottle and that, btw, there are 4 bottles on site!
.
.
.
.
.
.
.
.
.
Another pair of bottles found hiding on far side of house.

It's just such a preposterous explanation, and yet it is so.
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