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Old 24-11-2014, 14:25   #1
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Garmin xHD Radar Overlay

Hi all!

After purchasing a Garmin GMR xHD radar dome to go with OpenCPN radar overlay I realized that the protocol differs from
the GMR 18 HD reversed engineered and implemented by Dave.

So I went and bought a matching 721 plotter to be able to control the antenna.
I also got a mirroring Ethernet switch so that I will be able to monitor the traffic between the plotter and the antenna.

I have the ambition to reverse engineer this protocol as Dave has done with the gradar plugin.
At a first glance it looks like at least the commands are not that difficult to decode.

If this can be a joint effort together with the people here that's got knowledge of the gradar plugin I would be more than happy.

I am not really a software but a hardware electronics designer but have done some software coding when needed and I think I can understand the code for the gradar_pi.

/Hans
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Old 26-11-2014, 16:26   #2
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Re: Garmin xHD Radar overlay.

hasse_A...

I would be more than happy to help you R/E the new protocols. Its fiddly work, with some inspiration required. Feel free to bounce ideas in my direction as you proceed. I can help walk you through the PlugIn as required, also.

I think this project is do-able.

Good Luck

Dave
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Old 27-11-2014, 00:35   #3
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Re: Garmin xHD Radar overlay.

Nice Dave,

I have put together a spreadsheet with data command codes and suspected status words.

There seem to be a lot more packets sent across the Ethernet cable compared to the Garmin HD setup.

A lot of data sent from the antenna seem to be static.
At the moment I have 2 traces I am working on .
1) From power on until the plotter is ready to transmit. This is about a minute.
2) A short transmission period of a few seconds.

When I come home this evening I will post the spreadsheet.
It might need some explanation since it's not that well commented.
Every command from the plotter seem to generate 3 packets.
Could be for compatibility reasons.
The repetition rate of data sent from the antenna is 2 seconds when in standby.
The "old" commands are most likely there, but also a new set that seem to contain the same info.

I will check if it is doable to upload the traces. Haven't checked the size of them.

Cheers Hans
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Old 27-11-2014, 09:34   #4
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Re: Garmin xHD Radar overlay.

Ok, so here is the spreadsheet and
the pcap file for the 60 sec. start up as promised..

The Transmitt capture is to large (1.2 MB).
I will generate a smaller one later.

/Hans
Attached Files
File Type: pdf Packets.xls.pdf (43.0 KB, 113 views)
File Type: pdf Startup_66_sek.pcapng.pdf (533.5 KB, 69 views)
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Old 27-11-2014, 10:43   #5
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Re: Garmin xHD Radar overlay.

So her is smaller transmit capture.
/Hans
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File Type: pdf Transmit_2.pcapng.pdf (400.3 KB, 61 views)
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Old 27-11-2014, 11:50   #6
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Re: Garmin xHD Radar overlay.

Dave

I have attached a picture.
I am thinking of setting up something like this.

The idea is to be able to run control the radar either from the plotter or PC.
I will also be able to drop messages I believe are irrelevant.
It's easy to trace any ethernet port also.
I will of course have to do some winsock programming.
What do you think ? Is it useful and worth the effort ?

/Hans
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Old 27-11-2014, 13:58   #7
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Re: Garmin xHD Radar overlay.

A nice breakthrough!
Looks like most of the low frequent packets from the antenna are status reports where the pkt_type corresponds to the given command.
/Hans
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Old 27-11-2014, 18:43   #8
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Re: Garmin xHD Radar overlay.

Hans,
Thanks for making this happen. I was going to buy a HD radar a few years back, but the finances didnt work out. Anyway a xHD is in my future this spring and it would be great if it worked with O!!!
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Old 03-12-2014, 23:14   #9
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Re: Garmin xHD Radar overlay.

Here's an update!

What is working ?
1) Manual Range control
2) Manual Gain control
3) Dome offset
4) Scan Speed

All these are functioning and can be set from either the gxradar program or the plotter. Also, the respond from the scanner is updated to the "other" controller.
I.e. If a change is made on the plotter the respond from the scanner is updated in gxradar or the other way around.

Whats next ?

I will in the near future implement the noise control (sea and rain clutter).

I want to get rid of (fix them to the known commands) as many respond messages as possible before I take on the task of finding out what packet(s) holds the scanner status.
It seems as if for every command there are mostly 3 packets sent to the scanner. However, only one of them is significant.

What may I need help with ?

There must be a change in the GUI at certain places.
On the xHd scanner there are a few more functions.
1) There are 2 auto gain's High and Low. Not just 1.
2) You are able to set a no transmit sector.

This must be added to the widgets. I have no experience of writing
GUI's so there can be a need for help to get things moving a bit faster.
Otherwise I will have to do some reading.

The scanner is lying on my basement floor and will not go onto the boat until April or so. This means I will have trouble getting live radar scan data earlier than that. During the time up until then I will be doing whatever can be done to get everything else working.

/Hans
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Old 05-12-2014, 02:40   #10
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Re: Garmin xHD Radar overlay.

Dave

Things are working out just fine.
I have almost implemented all the noise return messages from the scanner.

Now I need to change the menus since the functionality of the xHD is different compared to the HD scanner.

I have been reading up on wxWidgets and vxFormBuilder.
Do you have the project file (.fbp) for the gradar plugin I could start of from so i won't have to do it from scratch ?

/Hans
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Old 05-12-2014, 09:34   #11
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Re: Garmin xHD Radar overlay.

Quote:
Originally Posted by hasse_A View Post
Dave

Things are working out just fine.
I have almost implemented all the noise return messages from the scanner.

Now I need to change the menus since the functionality of the xHD is different compared to the HD scanner.

I have been reading up on wxWidgets and vxFormBuilder.
Do you have the project file (.fbp) for the gradar plugin I could start of from so i won't have to do it from scratch ?

/Hans
Hans

Here is the .fbp file you are looking for.

Chuck
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File Type: doc GRadarDialog.7z.doc (6.7 KB, 60 views)
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Old 05-12-2014, 10:15   #12
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Re: Garmin xHD Radar overlay.

Thank you Chuck!

Unzipped, loaded, code generated and compared. Found to be equal .
Great.

/Hans
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Old 08-12-2014, 15:16   #13
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Re: Garmin xHD Radar Overlay

Well, things are moving along quite nicely.

Range, Noise and Dome Control menus are now working in
the sense that setting control buttons or sliders in gxradar will
control the scanner and the Garmin plotter will update it's display
accordingly. I.e. I am running both as masters.

Not much more to be done there except I have a question
for you out there.

In the original gradar written by Dave, the sliders when set to
auto mode are not movable.
Is this the way we want it ?
I'd rather have the mode change from auto to manual when you
pull the slider. This is the way the Garmin plotter behaves.
I think we should aim for some kind of standard.

Any comment on this?

/Hans
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Old 08-12-2014, 15:27   #14
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Re: Garmin xHD Radar Overlay

Hans...

Your idea seems fine. When you touch the slider, it disables auto mode, and simply goes to manual.

Good idea
Dave
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Old 11-12-2014, 23:17   #15
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Re: Garmin xHD Radar Overlay

Quote:
Originally Posted by hasse_A View Post
Range, Noise and Dome Control menus are now working
Sentry mode with timed transmit is implemented and working.
I have added a menu for the "No transmit zone" and will soon
have that working as well.
This is an added functionality to the Garmin xHD scanner.

I will shortly post a screenshot of what the changed and added menu's look like.

/Hans
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