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Old 13-03-2014, 18:43   #1
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Join Date: Feb 2014
Location: Deland, Fl
Boat: Tartan, 4100, 41'
Posts: 4
Garmin GPS on OSX serial route uploads fail on 3.3.1419.

I have a new MacBook Pro running 3.3.1419 that I built using Xcode and wxWidgets 2.9.5. I have 3 Garmins, a 12XL, a GPSmap 76 and a GPSmap 76C. Serial input and output to all three devices fails on this laptop. The read for ACK after writing a command packet gets a NAK packet instead of the ACK. The Garmin spec. mentions that this might happen if the host is slow retrieving the ACK packet, it doesn't mention what happens if the read occurs too quickly. The spec. says that the operation should be retried with the appropriate retry and timeout logic. The GARMINHOST code doesn't check or handle NAKs as far as I can tell. It treats all link level problems as framing errors and gives up.

A quick fix is to insert a 5 millisec delay "usleep(5000)" at the end of GPS_Serial_Write_Packet just before the normal return. This quick hack results in correct position updates and route writes to the Garmin on a serial line. The proper fix is probably handling the NAK packet correctly, something I'll continue to look at.

There's also an issue with the 12XL. It's very old and is one of those Garmins that must be checked for route and waypoint overwrite. The logic is there to read the routes from the GPS checking for duplicates and then writing the new route back. The GARMINHOST logic works for the first 9 routes and then fails. I haven't investigated this further but did notice that the code assumes the unit has 10 routes when in fact the 12XL has 20.
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