GARMIN GPS Interface Specification

6.7. A400 – Proximity Waypoint Transfer Protocol
The Proximity Waypoint Transfer Protocol is used to transfer proximity waypoints between devices. When the Host
commands the GPS to send proximity waypoints, the GPS will send all proximity waypoints stored in its database.
When the Host sends proximity waypoints to the GPS, the Host may selectively transfer any proximity waypoint it
chooses.
The packet sequence for the Proximity Waypoint Transfer Protocol is shown below:
N Direction Packet ID Packet Data Type
0 Device1 → Device2 Pid_Records Records_Type
1 Device1 → Device2 Pid_Prx_Wpt_Data
2 Device1 → Device2 Pid_Prx_Wpt_Data
… … … …
n-2 Device1 → Device2 Pid_Prx_Wpt_Data
n-1 Device1 → Device2 Pid_Xfer_Cmplt Command_Id_Type
The first and last packets (Packet 0 and Packet n-1) are the standard beginning and ending packets (see Section 5.3,
Standard Beginning and Ending Packets, on page 12). The Command_Id_Type value contained in Packet n-1 is
Cmnd_Transfer_Prx, which is also the command value used by the Host to initiate a transfer of proximity waypoints
from the GPS.
Packets 1 through n-2 (Pid_Prx_Wpt_Data) each contain data for one proximity waypoint, which is provided in
product-specific data type . This data type usually contains the same waypoint data that is transferred during
the Waypoint Transfer Protocol, plus a valid proximity alarm distance.
Some units (e.g. aviation panel mounts) require a delay of one or more seconds between proximity waypoints when
the host transfers Prx waypoints to the unit.
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