mavlink parameters: try to send 5 params at once on USB & UDP connections

This further speeds up param loading.

On Pixracer via USB, it's possible to send up to 11 at once before the TX
buffer gets full, so there is still enough free bandwidth left.

src/modules/mavlink/mavlink_parameters.cpp

@@ -318,6 +318,21 @@ MavlinkParametersManager::handle_message(const mavlink_message_t *msg)
 
 void
 MavlinkParametersManager::send(const hrt_abstime t)
+{
+	if (_mavlink->get_protocol() == SERIAL && !_mavlink->is_usb_uart()) {
+		send_one();
+
+	} else {
+		// speed up parameter loading via UDP, TCP or USB: try to send 5 at once
+		int i = 0;
+
+		while (i++ < 5 && send_one());
+	}
+}
+
+
+bool
+MavlinkParametersManager::send_one()
 {
 	bool space_available = _mavlink->get_free_tx_buf() >= get_size();
 
@@ -374,7 +389,7 @@ MavlinkParametersManager::send(const hrt_abstime t)
 
 		/* skip if no space is available */
 		if (!space_available) {
-			return;
+			return false;
 		}
 
 		/* The first thing we send is a hash of all values for the ground
@@ -397,7 +412,7 @@ MavlinkParametersManager::send(const hrt_abstime t)
 			_send_all_index = 0;
 
 			/* No further action, return now */
-			return;
+			return true;
 		}
 
 		/* look for the first parameter which is used */
@@ -415,6 +430,10 @@ MavlinkParametersManager::send(const hrt_abstime t)
 
 		if ((p == PARAM_INVALID) || (_send_all_index >= (int) param_count())) {
 			_send_all_index = -1;
+			return false;
+
+		} else {
+			return true;
 		}
 
 	} else if (_send_all_index == PARAM_HASH && hrt_absolute_time() > 20 * 1000 * 1000) {
@@ -422,6 +441,8 @@ MavlinkParametersManager::send(const hrt_abstime t)
 		_mavlink->send_statustext_critical("WARNING: SYSTEM BOOT INCOMPLETE. CHECK CONFIG.");
 		_mavlink->set_boot_complete();
 	}
+
+	return false;
 }
 
 int