I've been working with a developer for the past two weeks or so who wrote a program in Python called "jdmtool", his tool originally only supported the Garmin GNS400/500 series devices in that the software would go up to the Jeppesen site, download the current database and write it out to the Garmin flash drive. 

After going back and forth for a while we have figured out the format of the navdata.dsf (and obstacle.dsf) files along with all of the values in the .jdm file, from that he has incorporated the ability to download the database data from Jeppesen and write it out to a USB thumbdrive duplicating what the Jeppesen JDM program does.  The speed of the jdmtool vs the official JDM program is similar (slow) even though the jdmtool is written in Python.  

The current package will be uploaded to PyPI soon ( http://pypi.org/project/jdmtool/" rel="nofollow - http://pypi.org/project/jdmtool/ ), and currently the readme file on github only references the Garmin devices.  However if you want to run the software and write out the Avidyne databases here are the updated instructions -

Keep in mind the software DOES NOT bypass Jeppesen's login requirements, you still must have a valid login and current subscription to access the databases.

First the software is located here - http://github.com/dimaryaz/jdmtool" rel="nofollow - http://github.com/dimaryaz/jdmtool

Follow the install instructions to install the latest code from GitHub

Next go to the "Basic Usage" section

Perform  login with you Jeppesen credentials and follow all the steps except when you get to the "Transfer the database to the data card" use this syntax instead -

At that point the software will create the dsf and .jdm files, encode them with the required checksums and write the file to the thumbdrive.  Next simply unmount the thumbdrive and install it on the IFD as normal.

Important, the resulting navdata.dsf file will be a slightly different size from the navdata.dsf file from Jeppesen, this is due to how JDM and jdmtool compress the data, both tools are using the same compression type (zlib) however the compression options are different but will uncompress and extract to the same size/data set on the IFD and the IFD doesn't care what options were used as long as the file uses zlib for its compression and all the checksums match correctly.

Also the obstacle database is coming shortly, it is already in the software but hasn't been tested yet.

Maybe it'll be possible to write the databases out simply using a cell phone and an OTG cable... time will tell. :-)

-PA

I followed the instruction on github and was able to connect to Jeppesen, see and download my subscriptions.

Having problems downloading them to my Skybound / garmin card and other USB sticks. Will file a bug report.

The only one I've tested is the navdata for the US only, so I wonder if more has to be done to update anything other than the US?

I'm sure he is going to need the services.xml file which is ~/.local/share/jdmtool/services.xml  remove any personally identifying information... eg customer number, tail number, email, name

Seems that my issue is that I have a non-waas card, so its layout is quite different.

If I'm reading correctly it looks like your issue is not with the Avidyne databases but rather with the Garmin databases, either you have the WAAS unit and the developer doesn't or vice versa and the databases are different.

PA