AP_Mount: added sending of attitude and velocity for SIYI

will be used by SIYI for improved gimbal control

libraries/AP_Mount/AP_Mount_Siyi.cpp

@@ -82,6 +82,12 @@ void AP_Mount_Siyi::update()
         _last_rangefinder_req_ms = now_ms;
     }
 
+    // send attitude to gimbal at 10Hz
+    if (now_ms - _last_attitude_send_ms > 100) {
+        _last_attitude_send_ms = now_ms;
+        send_attitude();
+    }
+    
     // run zoom control
     update_zoom_control();
 
@@ -1087,4 +1093,31 @@ void AP_Mount_Siyi::check_firmware_version() const
     }
 }
 
+/*
+ send ArduPilot attitude to gimbal
+*/
+void AP_Mount_Siyi::send_attitude(void)
+{
+    const auto &ahrs = AP::ahrs();
+    struct {
+        uint32_t time_boot_ms;
+        float roll, pitch, yaw;
+        float rollspeed, pitchspeed, yawspeed;
+    } attitude;
+
+    // get attitude as euler 321
+    const auto &gyro = ahrs.get_gyro();
+    const uint32_t now_ms = AP_HAL::millis();
+
+    attitude.time_boot_ms = now_ms;
+    attitude.roll = ahrs.roll;
+    attitude.pitch = ahrs.pitch;
+    attitude.yaw = ahrs.yaw;
+    attitude.rollspeed = gyro.x;
+    attitude.pitchspeed = gyro.y;
+    attitude.yawspeed = gyro.z;
+
+    send_packet(SiyiCommandId::EXTERNAL_ATTITUDE, (const uint8_t *)&attitude, sizeof(attitude));
+}
+
 #endif // HAL_MOUNT_SIYI_ENABLED

libraries/AP_Mount/AP_Mount_Siyi.h

@@ -111,6 +111,7 @@ private:
         ABSOLUTE_ZOOM = 0x0F,
         SET_CAMERA_IMAGE_TYPE = 0x11,
         READ_RANGEFINDER = 0x15,
+        EXTERNAL_ATTITUDE = 0x22,
     };
 
     // Function Feedback Info packet info_type values
@@ -324,6 +325,10 @@ private:
     uint32_t _last_rangefinder_dist_ms;             // system time of last successful read of rangefinder distance
     float _rangefinder_dist_m;                      // distance received from rangefinder
 
+    // sending of attitude to gimbal
+    uint32_t _last_attitude_send_ms;
+    void send_attitude(void);
+
     // hardware lookup table indexed by HardwareModel enum values (see above)
     struct HWInfo {
         uint8_t hwid[2];