Parser for wMBus messages send from the Lobaro LoRaWAN Bridge

wMBusBrigeParser.go

// one cache per appId with max 9 messages
var msgCache = make(map[string][9]types.UplinkMessage, 0)

func ttnWmbusBridgeHandler(req *types.UplinkMessage) {
   // Collect messages in memory until last piece and create a complete wmbus message

   if req.FPort >= 11 && req.FPort <= 99 {
      if _, ok := msgCache[req.AppID]; !ok {
         msgCache[req.AppID] = [9]types.UplinkMessage{}
      }

      part := int(req.FPort / 10)
      total := int(req.FPort % 10)

      logrus.WithField("part", part).WithField("total", total).Info("Got wmbus message part")
      cache := msgCache[req.AppID]
      cache[part-1] = *req
      msgCache[req.AppID] = cache

      if part == total {
         logrus.Info("Got last piece, build wmbus message")
         cache := msgCache[req.AppID]
         delete(msgCache, req.AppID) // Free some memory
         expectedFCnt := cache[0].FCnt
         wmbusMsg := make([]byte, 0)
         for i := 0; i < total; i++ {
            if cache[i].FCnt != expectedFCnt {
               logrus.Info("Failed to create wmbus message, bad FCnt")
               return
            }
            expectedFCnt++
            wmbusMsg = append(wmbusMsg, cache[i].PayloadRaw...)
         }
         // Done got full wmbusMsg
         wmbusMsgBase64 := base64.StdEncoding.EncodeToString(wmbusMsg)
         logrus.WithField("msgBase64", wmbusMsgBase64).WithField("parts", total).Info("Got full wmbus message")
         
         // TODO: Do something with the data (wmbusMsgBase64)

      }
   } else {
      delete(msgCache, req.AppID)
   }
}