GCS_MAVLink: add support for AIRSPEED message

libraries/GCS_MAVLink/GCS.h

@@ -27,6 +27,7 @@
 #include <AP_Winch/AP_Winch_config.h>
 #include <AP_AHRS/AP_AHRS_config.h>
 #include <AP_Arming/AP_Arming_config.h>
+#include <AP_Airspeed/AP_Airspeed_config.h>
 
 #include "ap_message.h"
 
@@ -360,6 +361,12 @@ public:
     void send_scaled_pressure();
     void send_scaled_pressure2();
     virtual void send_scaled_pressure3(); // allow sub to override this
+#if AP_AIRSPEED_ENABLED
+    // Send per instance airspeed message
+    // last index is used to rotate through sensors
+    void send_airspeed();
+    uint8_t last_airspeed_idx;
+#endif
     void send_simstate() const;
     void send_sim_state() const;
     void send_ahrs();

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -1125,6 +1125,9 @@ ap_message GCS_MAVLINK::mavlink_id_to_ap_message_id(const uint32_t mavlink_id) c
 #endif
 #if AP_MAVLINK_MSG_RELAY_STATUS_ENABLED
         { MAVLINK_MSG_ID_RELAY_STATUS, MSG_RELAY_STATUS},
+#endif
+#if AP_AIRSPEED_ENABLED
+        { MAVLINK_MSG_ID_AIRSPEED, MSG_AIRSPEED},
 #endif
             };
 
@@ -2327,6 +2330,58 @@ void GCS_MAVLINK::send_scaled_pressure3()
     send_scaled_pressure_instance(2, mavlink_msg_scaled_pressure3_send);
 }
 
+#if AP_AIRSPEED_ENABLED
+void GCS_MAVLINK::send_airspeed() 
+{
+    AP_Airspeed *airspeed = AP_Airspeed::get_singleton();
+    if (airspeed == nullptr) {
+        return;
+    }
+
+    for (uint8_t i=0; i<AIRSPEED_MAX_SENSORS; i++) {
+        // Try and send the next sensor
+        const uint8_t index = (last_airspeed_idx + 1 + i) % AIRSPEED_MAX_SENSORS;
+        if (!airspeed->enabled(index)) {
+            continue;
+        }
+
+        float temperature_float;
+        int16_t temperature = INT16_MAX;
+        if (airspeed->get_temperature(index, temperature_float)) {
+            temperature = int16_t(temperature_float * 100);
+        }
+
+        uint8_t flags = 0;
+        // Set unhealthy flag
+        if (!airspeed->healthy(index)) {
+            flags |= 1U << AIRSPEED_SENSOR_FLAGS::AIRSPEED_SENSOR_UNHEALTHY;
+        }
+
+        // Set using flag if the AHRS is using this sensor
+        const AP_AHRS &ahrs = AP::ahrs();
+        if (ahrs.using_airspeed_sensor() && (ahrs.get_active_airspeed_index() == index)) {
+            flags |= 1U << AIRSPEED_SENSOR_FLAGS::AIRSPEED_SENSOR_USING;
+        }
+
+        // Assemble message and send
+        const mavlink_airspeed_t msg {
+            airspeed    : airspeed->get_airspeed(index),
+            raw_press   : airspeed->get_differential_pressure(index),
+            temperature : temperature,
+            id          : index,
+            flags       : flags
+        };
+
+        mavlink_msg_airspeed_send_struct(chan, &msg);
+
+        // Only send one msg per call
+        last_airspeed_idx = index;
+        return;
+    }
+
+}
+#endif
+
 #if AP_AHRS_ENABLED
 void GCS_MAVLINK::send_ahrs()
 {
@@ -6288,6 +6343,13 @@ bool GCS_MAVLINK::try_send_message(const enum ap_message id)
         send_scaled_pressure3();
         break;
 
+#if AP_AIRSPEED_ENABLED
+    case MSG_AIRSPEED:
+        CHECK_PAYLOAD_SIZE(AIRSPEED);
+        send_airspeed();
+        break;
+#endif
+
     case MSG_SERVO_OUTPUT_RAW:
         CHECK_PAYLOAD_SIZE(SERVO_OUTPUT_RAW);
         send_servo_output_raw();

libraries/GCS_MAVLink/ap_message.h

@@ -100,5 +100,6 @@ enum ap_message : uint8_t {
 #if AP_MAVLINK_MSG_HIGHRES_IMU_ENABLED
     MSG_HIGHRES_IMU,
 #endif
+    MSG_AIRSPEED,
     MSG_LAST // MSG_LAST must be the last entry in this enum
 };