AP_GPS: update implementation of SBP2 flags

Some flags were out of date or named incorrectly.

Updates based on protocol version 2.4.1, documented here:
b02e8d835c/docs/sbp.pdf

libraries/AP_GPS/AP_GPS_SBP2.cpp

@@ -271,14 +271,14 @@ AP_GPS_SBP2::_attempt_state_update()
         //
         // Check Flags for Valid Messages
         //
-        if (last_gps_time.flags.fix_mode    == 0 ||
-            last_vel_ned.flags.fix_mode     == 0 ||
+        if (last_gps_time.flags.time_src    == 0 ||
+            last_vel_ned.flags.vel_mode     == 0 ||
             last_pos_llh.flags.fix_mode     == 0 ||
             last_dops.flags.fix_mode        == 0) {
 
             Debug("Message Marked as Invalid. NO FIX! Flags: {GPS_TIME: %d, VEL_NED: %d, POS_LLH: %d, DOPS: %d}",
-                   last_gps_time.flags.fix_mode,
-                   last_vel_ned.flags.fix_mode,
+                   last_gps_time.flags.time_src,
+                   last_vel_ned.flags.vel_mode,
                    last_pos_llh.flags.fix_mode,
                    last_dops.flags.fix_mode);
 

libraries/AP_GPS/AP_GPS_SBP2.h

@@ -88,7 +88,8 @@ private:
         uint8_t res : 5;
         uint8_t protocol_minor : 8;
         uint8_t protocol_major : 8;
-        uint8_t res2 : 7;
+        uint8_t res2 : 6;
+        bool ext_antenna_short : 1;
         bool ext_antenna : 1;
     }; // 4 bytes
 
@@ -98,7 +99,7 @@ private:
         uint32_t tow;    //< GPS Time of Week rounded to the nearest ms (unit: ms)
         int32_t ns;      //< Nanosecond remainder of rounded tow (unit: ns)
         struct PACKED flags {
-            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX
+            uint8_t time_src:3;  //< Fix mode (0: invalid, 1: GNSS Solution, 2: Propagated
             uint8_t res:5;       //< Reserved
         } flags;
     }; // 11 bytes
@@ -112,7 +113,7 @@ private:
         uint16_t hdop;   //< Horizontal Dilution of Precision (unit: 0.01)
         uint16_t vdop;   //< Vertical Dilution of Precision (unit: 0.01)
         struct PACKED flags {
-            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX
+            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX, 5: Undefined, 6: SBAS Position
             uint8_t res:4;       //< Reserved
             bool raim_repair:1;  //< Solution from RAIM?
         } flags;
@@ -128,9 +129,9 @@ private:
         uint16_t v_accuracy;  //< Vertical position accuracy estimate (unit: mm)
         uint8_t n_sats;       //< Number of satellites used in solution
         struct PACKED flags {
-            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX
-            uint8_t res:4;       //< Reserved
-            bool raim_repair:1;  //< Solution from RAIM?
+            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX, 5: Dead Reckoning, 6: SBAS Position
+            uint8_t ins_mode:2;  //< Inertial navigation mode (0: none, 1: INS used)
+            uint8_t res:3;       //< Reserved
         } flags;
     }; // 34 bytes
 
@@ -144,8 +145,9 @@ private:
         uint16_t v_accuracy;   //< Vertical velocity accuracy estimate (unit: mm/s)
         uint8_t n_sats;        //< Number of satellites used in solution
         struct PACKED flags {
-            uint8_t fix_mode:3;  //< Fix mode (0: invalid, 1: SPP, 2: DGNSS, 3: Float RTX, 4: Fixed RTX
-            uint8_t res:5;       //< Reserved
+            uint8_t vel_mode:3;  //< Velocity mode (0: Invalid, 1: Measured Doppler derived, 2: Computed Doppler derived, 3: Dead reckoning)
+            uint8_t ins_mode:2;  //< Inertial navigation mode (0: none, 1: INS used)
+            uint8_t res:3;       //< Reserved
         } flags;
     }; // 22 bytes
 
@@ -159,6 +161,7 @@ private:
             uint8_t quality:1;     //< Time quality values (0: Unknown - don't have nav solution, 1: Good (< 1 microsecond))
             uint8_t res:6;         //< Reserved
         } flags;
+        uint8_t pin;           //< Pin number (0-9)
     }; // 12 bytes
 
     void _sbp_process();