See this page for the background: Garmin Packet Analysis Packet 3215 at time stamp 245.534965 is the initiation of the transfer of the routes. On the iPad I used Garmin BlueChart to transfer tracks from the GPSMAP 5212 to the iPad. This is the start of communication request packet. The destination port on the Garmin is 50610. Packet 3216 is the acknowledgement (ACK) of the port opening. Packet 3217 - Ack of the Ack? Packet 3218 - Actual data sent from ipad to Garmin. 3f 08 ef be 02 00 00 00 b2 c5 Packet 3228 - ACK of 3218. Took more time that last ACK so it did something. Packet 3229 - Actual data sent from ipad to Garmin again. b7 08 ef be 01 00 00 00 01 Packet 3236 - ACK of 3229 * Delay here while I walk over to the Garmin and touch OK for the transfer to start * Packet 3413 - Data from Garmin to iPad; 40 08 ef be 00 00 00 00 Packet 3418 - ACK to Prior Packet 3419 - Data from iPad to Garmin 41 08 ef be 00 00 00 00 Notice the data is almost identical to 3413 - Exchanging of a confirmation or secret? Packet 3431 - ACK to Prior Packet 3433 - Data Garmin to iPad b8 08 ef be 01 00 00 00 01 Starting to see patterns. Notice the 08 EF BE are consistent? Packet 3434 - ACK to Prior Packet 3435 - Data iPad to Garmin. ba 08 ef be 00 00 00 00 Packet 3436 - The data starts flowing .... And goes all the way through Packet 3497. You can see some text in these packets. e.g. Big Fisher and Detroit are text. "Broad Cut" is a cut and it is very near N42.57156 W082.66702 I should be able to get the data from that track and use it to figure out the data structure. Of course I left the chip in the GPS .. and the iPad will not export the GPX version so I can't see the details of the track! Argh. (Did I miss some iPad functionality?) The packets below seem like some sort of keep alive. Packet 3498 - ACK and data from iPad to Garmin ba 08 ef be 00 00 00 00 this is a duplicate of 3435. * Note there is a 10 second gap at this point * (at this point I am going to stop tracking ACKs) Packet 3774 - Garmin to iPad 40 08 ef be 00 00 00 00 Duplicate of 3413 Packet 3776 - iPad to Garmin 41 08 ef be 00 00 00 00 Duplicate of 3419 * Note there is a 5 second gap here * Packet 3921 - iPad to Garmin 40 08 ef be 00 00 00 00 Packet 3922 - Garmin to iPad 41 08 ef be 00 00 00 00 * Note there is a 10 second gap here * Packet 4188 - Garmin to iPad 40 08 ef be 00 00 00 00 Packet 4190 - iPad to Garmin 41 08 ef be 00 00 00 00 * Note there is a 5 second gap here * Packet 4333 - iPad to Garmin 40 08 ef be 00 00 00 00 Packet 4334 - Garmin to iPad 41 08 ef be 00 00 00 00 |