Basic Workflow

1. The gateway remains in power-saving mode most of the time.
2. The unit wakes up at flexible configurable time points, e.g. every hours, every 7th day or every Monday.
3. Encrypted wireless M-Bus (868 MHz) telegrams are received for a configurable duration and buffered.
   1. Reception can be limited to certain devices and types by means of filters.
4. After the configured collection duration has been reached, the meter data reception is stopped again.
5. The buffered meter telegrams get uploaded afterwards on the Internet
   1. NB-IoT, LTE-M1: Data is send using UDP, DTLS (optional) and CoAP to the Lobaro IoT platform instance. 
   2. LoRaWAN: Data is send as Class A uplinks to the downstream LoRaWAN server / platform on the internet. Metering telegrams may be spliced and send in multiple uplinks.
6. The Lobaro Platform can perform decryption the consumption telegrams with stored keys.
7. The consumption values are available in table views inside the Lobaro Platform and as a CSV download 
8. Data may be forwarded from the Lobaro Platform to additional systems and platforms using one of these APIs: MQTT, REST, HTTPS-PUSH or SFTP.

Network Selection Parameters

WAN

This parameter can be used to set whether cellular IoT (NB-IoT, LTE-M) or LoraWAN is to be used for data transmission. With LoRaWAN, the type of network join can also be defined (ABP vs. OTAA). 

WAN

lte

Compatible wireless meter protocols

• Wireless M-BUS S1, C1 or T1 modes, e.g. unidirectional 868 MHz modes following DIN EN 13757-4.
• Open metering specification (OMS, Annex O): PHY_A - 868 MHz (uplink only)
• Sensus RF Bubble UP - Manufacturer specific radio protocol (Xylem Inc.)
• ME-Funk - Manufacturer specific radio protocol (Müller-electronic GmbH). Decoding of telegrams needs the Lobaro Platform.

433 MHz variants available on special sales request:

• Open metering specification (OMS, Annex O): PHY_B - 433 MHz (uplink only)
• Sensus RF Bubble UP 433 MHz - Manufacturer specific (Xylem Inc.) radio protocol

Anbindung an das Smart Meter Gateway (SMGW)

• SMGW Anbindung 🇩🇪

Configuration

Lobaro delivers all devices with a reasonable default configuration. Customer specific configurations are possible in different ways:

• Using our free Lobaro Maintenance Tool and the USB PC configuration adapter to be connected to the "config" connector on the hardware. Not accessible in the waterproof version of the Solar Gateway.
• Remotely in the field using LoRaWAN downlink messages.
• Remotely using NB-IoT via the Lobaro Platform.

Remote Configuration

• Devices using LTE-M or NB-IoT can be configured easily using the interface (search for 'config tab' inside devices) in the Lobaro Platform.
• Devices using LoRaWAN can configured by sending downlinks on port 128:
  • A single config parameter can be changed by sending S<parameter>=<value>
  • For example: changing the device to switch to using LTE-M or NB-IoT, you would change the parameter "WAN" to "lte" by sending:
    "SWAN=lte"
  • Depending on the used LoRaWAN network servers convention you will to encode this string in Base64 as "U1dBTj1sdGU=" or Hex as "5357414e3d6c7465".
  • AdditionalI Information: LoRaWAN Downlink Configuration

Config Parameters

LoRaWAN

The connection to the LoRaWAN network is defined by multiple configuration parameters. This need to be set according to your LoRaWAN network and the way your device is supposed to be attached to it, or the device will not be able to send any data.

For a detailed introduction into how this values need to be configured, please refer to the chapter LoRaWAN configuration in our LoRaWAN background article.

Name	Description	Type	Values	Default Value	Version
OTAA	Activation: OTAA or ABP	bool	true= use OTAA, false= use ABP
DevEUI	DevEUI used to identify the Device	byte[8]	e.g. 0123456789abcdef
JoinEUI	Used for OTAA (called AppEUI in v1.0)	byte[8]	e.g. 0123456789abcdef
AppKey	Key used for OTAA (v1.0 and v1.1)	byte[16]
NwkKey	Key used for OTAA (v1.1 only)	byte[16]
SF	Initial / maximum Spreading Factor	int	7 - 12	12	Removed since ???
ADR	Use Adaptive Data Rate	bool	true= use ADR, false= don't	true	Removed since ???
OpMode	Operation Mode	string	A= Class A, C= Class C		Removed since ???
TimeSync	Days after which to sync time	int	days, 0=don't sync time
RndDelay	Random delay before sending	int	max seconds
RemoteConf	Support Remote Configuration	bool	true=allow, false=deactivate	true	Removed since ???
LostReboot	Days without downlink before reboot	int	days, 0=don't reboot	5
payloadFormat	wMBUS Bridge LoRaWAN Payload Format	int	0= Encoding in ports, 1= prefixed with time, 2= prefixed with time and rssi
loraMaxMsgSize	Max. LoRa msg size before split (Payload Format 0 only)	int	10-50 (bytes)	50

NB-IoT

wMBUS

^† See also our Introduction to Cron expressions.

LoRaWAN

Uplink Payload formats

After collecting wireless M-Bus telegrams over the air, the Bridge starts uploading data via LoRaWAN. There exist two data formats that are transmitted over different LoRaWAN ports. As LoRaWAN can only transmit very short messages, the message formats contain only data bytes. The meaning of a byte is determined by its position within a message. The following describes the package formats used by the wireless M-Bus Bridge.

M-Bus telegrams can be longer as the maximal size of a LoRaWAN-Message. For this cases, the Bridge needs to split a telegram into multiple pieces and upload it using multiple LoRaWAN-Messages. There are two different methods this is done, according by the Payload Format you set in the Bridge's configuration.

Payload Format 0 is focused on easy reassembly of the pieces. The parts are encoded by port numbers and the data can just be concatenated together. Payload Formats 1 and 2 add additional information to the telegram. They focus on putting as much of a telegram in a single LoRaWAN-Message as possible with respecting the current Spreading Factor.

Status Packet (Port 1)

Port 1 - In order to provide some information about the health & connectivity state of the device itself, the device sends a status update at a daily basis. The status packet is sent on the first upload phase after activation of the device (after reboot) and then repeatedly in every upload phase that takes place a day or longer after the previous status packet. It has a length of 7 or 8 bytes. The battery voltages and ambient temperature are encodes as 16 bit integer using little endian encoding.

We provide a JavaScript reference implementation of a decoder for this status packet on GitHub, which can be used directly for decoding in The Things Network.

Data Packet (Port 11-99, PayloadFormat 0) - Default

After each wMBUS collecting phase, all saved telegrams (up to 500 can be stored) will be uploaded via LoRaWAN uplink messages as fast as possible. The received wMBUS telegrams that did pass the configured white list filters will be uploaded without any modification in one or more LoRaWAN messages. If a wMBUS telegram is bigger than the bridge configuration parameter loraMaxMsgSize the transmission will be done using multiple LoRaWAN messages. This parameter is limited to ≤ 50 bytes due to LoRaWANs maximum payload size restrictions. In case of telegram splitting is needed the receiving backend application server as to reassemble the original wMBUS telegram before decryption & parsing of the meter data. This is done by simply joining the messages together in the order of receive. The LoRaWAN port encodes identifies a LoRaWAN fragment of the original wireless M-Bus telegram. This way partial messages can be identified using the LoRaWAN Port:

• 10 < LoRaWAN Port < 100 ≡ (Part Number | Total Parts)

Gaps in the LoRaWAN Frame Counter are giving a hint for missing telegram parts which can happen in LoRaWAN since it's a ALOHA based protocol, e.g. collisions and some packet losses are accepted by principle of operation. In case the backend noticed a missing packet the wMBUS telegram can't be assembled anymore as described before.

Examples

Examples (with loraMaxMsgSize = 50):

• A 48 Byte wMBUS telegram will be send on LoRaWAN port 11. Port 11 says it is the first message of only one message (no splitting).
• A 75 byte wMBUS telegram will be send in two messages on LoRaWAN ports 12 and 22. Port 12 means this part one of a wMBUS telegram that got splitted into two LoRaWAN messages. Port 22 means that this data is the 2^nd part of the original wMBUS data. Both parts have to been concatenated in the order of receive by the backend.
• A 101 byte wMBUS telegram will be send in three messages on LoRaWAN ports 13, 23 and 33. Port 13 means this part one of a wMBUS telegram that got splitted into three LoRaWAN messages. Port 23 means that this data is the 2^nd part of the original wMBUS data. Port 33 means that this data is the 3^rd part of the original wMBUS data. All three parts have to been concatenated in the order of receive by the backend.

Data Packet without Timestamp (Port 101, PayloadFormat 1)

When using Payload Format 1, collected telegrams are uploaded on a single Port: 101. For each telegram there will be added the timestamp of reception. The first byte of messages on Port 101 encodes splitting of messages as follows.

Splitting

Every Uplink on Port 101 is prefixed with a single byte, where the least significant Bit indicates if that Uplink is the first part of a message, and the second least significant Bit indicates if that Uplink is the last part or a message. So there are 4 different possible values for the first Byte of an Uplink on Port 101:

So each message sent on Port 101, whether it is contained in a single Uplink or spread over multiple ones, starts with an Uplink where the least significant Bit of the first Byte is set. Each Message ends with an Uplink where the second least significant Bit of the first Byte is set. In cases where the Message fits in a single Uplink, that Uplink is both first and last Uplink, and therefore both Bits are set.

The combination of those two Bits and the Frame Counter of the Uplinks makes it possible to upload Messages of any length while allowing the receiving side to now exactly, if a Message has been transferred completely, or if part of it is missing (when there are Frame Counter values missing).

The Bridge puts as many Bytes in each Uplink as possible for the current Spreading Factor, even if the Spreading Factor changes between Uplinks because of ADR.

When the data of all Uplinks that are part of a single Message are appended in order of reception (after removing the first Byte of each Uplink), you get the payload Data of a full message.

Payload (Format 1)

The Payload Data after reassembly of the split parts consists of a 5 Byte Timestamp, that marks the point in time the Bridge did receive that telegram, followed by the Data of the Telegram. The Timestamp follows the convention of all our 40bit-Timestamps; you can find the details under Timestamp in our LoRaWAN Background Information.

Examples

For easier understanding, the wMBus-Telegram in the examples will always be 0102030405060708090a0b0c0d0e0f.

Data Packet with Timestamp (Port 102, PayloadFormat 2)

Upload Format 2 works like Upload Format 1, with the same logic for splitting messages, but uploads are sent on Port 102. The Payload consists of a 5 Byte Timestamp marking the time of reception, followed by a uint_8 that holds the (negated) RSSI value for that reception, followed by the Data of the Telegram.

Examples

Upload Speed / Duration

The bridge has to work in compliance with the European SRD 868 1% duty-cycle regulations. This implies as a rule of thumb the device can upload at most wMBUS telegrams via LoRaWAN for 36 seconds every hour.

The actual transmit time ('ToA: time on air') for each LoRaWAN message depends on the byte size and the used LoRa spreading factor (SF) which defines how redundant LoRa data is send. This means a device with good connectivity and consequently using LoRa SF7 (ToA ≤ 0,050s) can upload much faster more data than a node using LoRa SF11 (ToA ≥ 1s) due to a hard to reach LoRaWAN gateway. The bridge will upload in conformity with the regulations automatically as fast as possible. When it has to wait it enters a low power sleep mode until the next transmission is possible again. The next data collection phase will be started only after completion of the previous upload phase in respect to the configured listenCron parameter. Because of this it is advisable to define the cron parameter with an estimation of the upload duration in mind. This will avoid unexpected 'skipping' of data collection phases.

Downlinks

Remote Configuration (Port 128)

Update of Configuration parameters is documented in our LoRaWAN downlink messages documentation.

Supported downlink messages:

• <name> is the ASCII encoded name of the parameter

• <value> is the ASCII encoded value

wMbus Bridge Commands (Port 132)

Ad-hoc readout

A downlink that triggers an Ad hoc readout, independent of CRON triggers. The Ad-hoc readout is using the same parameters (filters and listening duration) as a CRON triggered readout.

Decoding wMBUS telegrams

After receiving the raw wireless M-Bus telegrams from your LoRaWAN network provider the actual metering data has to be decrypted and decoded by a backend service for further processing. The details of this are described in the EN 13757 norm and the newer OMS specification, which is a clarification of the original underlying norm.

A universal wireless M-Bus decoder is a relatively complicated piece of software if you start implementing it from scratch since the norm covers many different use cases, units, meter types and data formats. If you know in advance the exact telegram format of the deployed meters in your setup a hard coded data decoding may be a feasible approach. This is because wireless M-Bus devices often send the same telegram format in every transmission. Please contact the manufacturer of your meters for the needed telegram format details.

An an alternative to support a quick evaluation of our hardware Lobaro offers a easy to use webservice which is designed to decode all sorts of wMBUS input data including decryption if the correct key has been provided. You can access the decoder service for free during testing. The API can be licensed for production usages.

Example Parser

TTN / Chripstack / Lobaro Platform / niota (see wrapper functions)

function readVersion(bytes, i) {
    if (bytes.length < 3) {
        return null;
    }
    return "v" + bytes[i] + "." + bytes[i + 1] + "." + bytes[i + 2];
}

function Decoder(bytes, port) {
    // Decode an uplink message from a buffer
    // (array) of bytes to an object of fields.
    var decoded = {};

    if (port === 9) {
        decoded.devStatus = bytes[0];
        decoded.devID = bytes[1] | bytes[2] << 8 | bytes[3] << 16 | bytes[4] << 24;
        decoded.dif = bytes[5];
        decoded.vif = bytes[6];
        decoded.data0 = bytes[7];
        decoded.data1 = bytes[8];
        decoded.data2 = bytes[9];
    }

    // example decoder for status packet by lobaro
    if (port === 1 && bytes.length == 9) { // status packet - old
        decoded.FirmwareVersion = String.fromCharCode.apply(null, bytes.slice(0, 5)); // byte 0-4
        decoded.Vbat = (bytes[5] | bytes[6] << 8) / 1000.0; // byte 6-7 (originally in mV)
        decoded.Temp = (bytes[7] | bytes[8] << 8) / 10.0; // byte 8-9 (originally in 10th degree C)
        decoded.msg = "Firmware Version: v" + decoded.FirmwareVersion + " Battery: " + decoded.Vbat + "V Temperature: " + decoded.Temp + "°C";
    } else if (port === 1 && bytes.length >= 7) {
        decoded.FirmwareVersion = readVersion(bytes, 0); // byte 0-2
        decoded.Vbat = (bytes[3] | bytes[4] << 8) / 1000.0; // originally in mV
        decoded.Temp = (bytes[5] | bytes[6] << 8) / 10.0; // originally in 10th degree C
        decoded.msg = "Firmware Version: " + decoded.FirmwareVersion + " Battery: " + decoded.Vbat + "V Temperature: " + decoded.Temp + "°C";
        if (bytes.length == 8) { // added in v2.5.0
            decoded.Flags = bytes[7];
        }
    }

    return decoded;
}

// Wrapper for Lobaro Platform
function Parse(input) {
    // Decode an incoming message to an object of fields.
    var b = bytes(atob(input.data));
    var decoded = Decoder(b, input.fPort);
 
    return decoded;
}
 
// Wrapper for Loraserver / ChirpStack
function Decode(fPort, bytes) {
    return Decoder(bytes, fPort);
}
 
// Wrapper for Digimondo niota.io
// Uncomment only when used in niota!
/*
module.exports = function (payload, meta) {
    const port = meta.lora.fport;
    const buf = Buffer.from(payload, 'hex');
 
    return Decoder(buf, port);
}*/