Garmin GPSMAP 820 MFD WIFI data format

[nrobertson77]

I'm trying to write software for an esp8266 micro controller board to receive NMEA data over wifi from a Garmin Gpsmap 820 mfd. The Garmin Android app connects to the boat wifi without a problem and mirrors the main display beautifully however I would like to know what data is sent over wifi from the Garmin? Is it standard NMEA sentences as well as the chart data and from what port and protocol (UDP/TCP). Finding the IP address of the MFD to listen to is not a problem as any Android phone/tablet connected to the wifi network gives me the Access Point IP.


The owner manual does not give the protocol/port no.



I already have the software for the ESP8266 running to receive the NMEA sentences sent from a B&G Zeus MFD (TCP and port 1011) over wifi so hopefully it's the same. I say hopefully as the new 46ft. yacht ordered for the charity I sail with on the Clyde in Scotland is 3/4 built in a factory in Germany and so will be VERY delayed.



I want acquire the raw data to allow me to program (among other things) an audio compass for the partially sighted and blind sailors we take out. I already have an audio compass app written and running on an Android phone so we know it will be of use.

Thanks for any help.
Neil

[smac999]

it's likely just streaming a video image with no raw data? but I could be wrong.

[nrobertson77]

Hi Smac99
Thanks for the quick reply..Appreciated however I Do think it’s sending more than just video. Here’s the app that is working and does a lot more than display the charts. I’ll get there eventually. Thanks

[nrobertson77]

Sorry forgot the link for the Active Captain app

https://buy.garmin.com/en-US/US/p/573254#overview

[rbhun]

Just out of interest, did you ever got this working? I thought of using Wireshark to capture data but never got around it.

Thanks

[nrobertson77]

Sorry never did get it to work. I don't get access to the boat thats fitted with the Garmin plotter very often to get a chance to do any investigation. It's kinda difficult to do it blind at home and then get on board for a few minutes and make no progress even to sniff out the data.


The Android app and the ESP8266 code that I wrote for the B&G plotter are working just fine and are being used. The B&G plotter is on an easy to find IP address and the port/protocol is documented where it just sends standard NMEA sentences. The audible call out of depth is particularly useful when running in and looking for a depth to drop anchor without having your eyes on an instrument.


Sorry cant help
Neil