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Has anyone worked with communicating with a Garmin GPS using their protocol?

I need to obtain current position (lat/long/elev) and Waypoint data from a Garmin GPSmap 76CS using the Garmin protocol. Read only, I do not need to write. Any help would be appreciated.
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Message 1 of 17
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If I've done my checking correctly, isn't the Garmin Protocol just a subset of serial protocol? All you should need to do is basic serial communication, just follow the standards of the protocol. What API or development environment do you plan on writing your application in? Are there any particular commands that you need to send, or are having trouble sending? Please let us know!

Logan S.
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Message 2 of 17
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Yes, the Garmin protocol is a serial interface, but it is not like using the NEMA messages. Each command has to be encoded using their protocol and the results have to be decoded. I need current position (elev,lat,long) and Waypoint data for inclusion into a LabView program. I can obtain the current position using NEMA but Waypoints require the Garmin protocol. I have been able to request the data but so far have not been able to interrupt it.
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Message 3 of 17
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If I've done my research correctly, it looks like you have basically two options for retrieving waypoint data:

1. Do a single read, and get the entire string of data and then parse through it in LabVIEW.
2. Do multiple reads, and get the individual elements piece by piece in LabVIEW.

It really depends on how confident you feel with your LabVIEW string manipulation skills which one you choose. I would probably recommend that you use the second option, simply because you can specify how many bytes of data you want for each piece. Here's what I was able to find:

Description# of bytes to read
Start of message1
Waypoint record ID1
Number of message bytes to follow1
Waypoint ID6
Latitude4
Longitude4
Time waypoint stored4
Waypoint comment40*
Checksum1
Message terminator2

*where the number of bytes that your read for the waypoint comment is determined by the following formula:
Number of message bytes to follow - Waypoint ID bytes - Latitude bytes - Longitude bytes - Time waypoint stored bytes

As you read each element you can then take the data that's returned and use the string to number conversion functions in LabVIEW as needed. There may still be more to this, but let me know what you are able to do with this information, or if any of the information is incorrect.

Logan S.
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Message 4 of 17
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I have attached a series of vis that I use to retrieve the waypoints from a Gecko Garmin gps. I think it should work with a 76CS model, although Garmin has the bad habit to change the data format quite often...
I also have some utilities to convert to UTM coordinates. Ask if you need them.

CC

Message Edited by chilly charly on 04-10-2005 07:25 AM

Message Edited by chilly charly on 04-10-2005 07:26 AM

Chilly Charly    (aka CC)
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Message 5 of 17
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I realise that the 76CS uses the new USB physical protocol. Don't know how this will affet the communication...
Please tell us your findings...

CC
Chilly Charly    (aka CC)
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Message 6 of 17
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Thanks for everyone's help. I took the easy way. I found a GPS Library of .net functions (Waymex GPS Library) which gives me everything I need. Once again thank you for your repsonses.
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Message 7 of 17
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Hello Dark Eagle,

Would you share your code for the garmin GPS with me?

I have an Etrex Legend C with a USB interface as well. I have downloaded the .net library as well, but don`t know how to use it.
Please give me a help on the way.

Thanks in advance,

Kind regards,
Ferry
(ferpet@zonnet.nl)
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Message 8 of 17
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could you please let me see the vis on how to convert to the utm coordinates

thank you vivi
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Message 9 of 17
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Attached is the vi I use to communicate with the Garmin GPSmap 76CS.  It is using Waymex .net library.
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Message 10 of 17
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