From 894bf2a23f856768370423d6a1b2fec7ce812ba4 Mon Sep 17 00:00:00 2001
From: Randy Mackay <rmackay9@yahoo.com>
Date: Mon, 18 Sep 2017 14:37:37 +0900
Subject: [PATCH] Rover: support SET_GPS_GLOBAL_ORIGIN message

---
 APMrover2/GCS_Mavlink.cpp | 21 +++++++++++++++++++++
 APMrover2/Rover.h         |  1 +
 APMrover2/commands.cpp    | 33 ++++++++++++++++++++++++++++++---
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/APMrover2/GCS_Mavlink.cpp b/APMrover2/GCS_Mavlink.cpp
index c1346bf6f9..5160cbc2e2 100644
--- a/APMrover2/GCS_Mavlink.cpp
+++ b/APMrover2/GCS_Mavlink.cpp
@@ -643,6 +643,23 @@ void GCS_MAVLINK_Rover::handle_change_alt_request(AP_Mission::Mission_Command &c
 void GCS_MAVLINK_Rover::handleMessage(mavlink_message_t* msg)
 {
     switch (msg->msgid) {
+
+    case MAVLINK_MSG_ID_SET_GPS_GLOBAL_ORIGIN:
+    {
+        mavlink_set_gps_global_origin_t packet;
+        mavlink_msg_set_gps_global_origin_decode(msg, &packet);
+        // sanity check location
+        if (!check_latlng(packet.latitude, packet.longitude)) {
+            break;
+        }
+        Location ekf_origin {};
+        ekf_origin.lat = packet.latitude;
+        ekf_origin.lng = packet.longitude;
+        ekf_origin.alt = packet.altitude / 10;
+        rover.set_ekf_origin(ekf_origin);
+        break;
+    }
+
     case MAVLINK_MSG_ID_REQUEST_DATA_STREAM:
         {
             handle_request_data_stream(msg, true);
@@ -829,6 +846,10 @@ void GCS_MAVLINK_Rover::handleMessage(mavlink_message_t* msg)
         case MAV_CMD_GET_HOME_POSITION:
             if (rover.home_is_set != HOME_UNSET) {
                 send_home(rover.ahrs.get_home());
+                Location ekf_origin;
+                if (rover.ahrs.get_origin(ekf_origin)) {
+                    send_ekf_origin(ekf_origin);
+                }
                 result = MAV_RESULT_ACCEPTED;
             } else {
                 result = MAV_RESULT_FAILED;
diff --git a/APMrover2/Rover.h b/APMrover2/Rover.h
index ba9e42149f..099d94bd6a 100644
--- a/APMrover2/Rover.h
+++ b/APMrover2/Rover.h
@@ -451,6 +451,7 @@ private:
     void update_home_from_EKF();
     bool set_home_to_current_location(bool lock);
     bool set_home(const Location& loc, bool lock);
+    void set_ekf_origin(const Location& loc);
     void set_system_time_from_GPS();
     void update_home();
 
diff --git a/APMrover2/commands.cpp b/APMrover2/commands.cpp
index 6761ddb741..08207e27b4 100644
--- a/APMrover2/commands.cpp
+++ b/APMrover2/commands.cpp
@@ -35,10 +35,10 @@ bool Rover::set_home(const Location& loc, bool lock)
         return false;
     }
 
-    // set EKF origin to home if it hasn't been set yet
+    // check if EKF origin has been set
     Location ekf_origin;
     if (!ahrs.get_origin(ekf_origin)) {
-        ahrs.set_origin(loc);
+        return false;
     }
 
     // set ahrs home
@@ -69,8 +69,9 @@ bool Rover::set_home(const Location& loc, bool lock)
     // log ahrs home and ekf origin dataflash
     Log_Write_Home_And_Origin();
 
-    // send new home location to GCS
+    // send new home and ekf origin to GCS
     gcs().send_home(loc);
+    gcs().send_ekf_origin(loc);
 
     // send text of home position to ground stations
     gcs().send_text(MAV_SEVERITY_INFO, "Set HOME to %.6f %.6f at %.2fm",
@@ -82,6 +83,32 @@ bool Rover::set_home(const Location& loc, bool lock)
     return true;
 }
 
+// sets ekf_origin if it has not been set.
+//  should only be used when there is no GPS to provide an absolute position
+void Rover::set_ekf_origin(const Location& loc)
+{
+    // check location is valid
+    if (!check_latlng(loc)) {
+        return;
+    }
+
+    // check if EKF origin has already been set
+    Location ekf_origin;
+    if (ahrs.get_origin(ekf_origin)) {
+        return;
+    }
+
+    if (!ahrs.set_origin(loc)) {
+        return;
+    }
+
+    // log ahrs home and ekf origin dataflash
+    Log_Write_Home_And_Origin();
+
+    // send ekf origin to GCS
+    gcs().send_ekf_origin(loc);
+}
+
 // checks if we should update ahrs/RTL home position from GPS
 void Rover::set_system_time_from_GPS()
 {