Correctly set fragment information

src/GPS/RTCM/RTCMMavlink.cc

@@ -41,16 +41,25 @@ void RTCMMavlink::RTCMDataUpdate(QByteArray message)
         memcpy(&mavlinkRtcmData.data, message.data(), message.size());
         sendMessageToVehicle(mavlinkRtcmData);
     } else {
-        //we need to fragment
+        // We need to fragment
+
+        static uint8_t sequenceId = 0;  // Sequence id is used to indicate that the individual fragements belong to the same set
+        uint8_t fragmentId = 0;         // Fragment id indicates the fragement within a set
+
         int start = 0;
         while (start < message.size()) {
             int length = std::min(message.size() - start, maxMessageLength);
-            mavlinkRtcmData.flags = 1; //fragmented
+            mavlinkRtcmData.flags = 1;                      // LSB set indicates messsage is fragmented
+            mavlinkRtcmData.flags |= fragmentId++ << 1;     // Next 2 bits are fragment id
+            mavlinkRtcmData.flags |= sequenceId++ << 3;     // Next 5 bits are sequence id
             mavlinkRtcmData.len = length;
             memcpy(&mavlinkRtcmData.data, message.data() + start, length);
             sendMessageToVehicle(mavlinkRtcmData);
             start += length;
         }
+        if (sequenceId == 0x1F) {
+            sequenceId = 0;
+        }
     }
 }