M-BUS-2 / User Manual
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Revision 07 - 14 September 2020
5 COMMUNICATION PROTOCOL
This part describes the M-BUS-2 data exchange protocol with LoRaWAN network.
In fields consisting of several bytes, the little-endian byte order is used
CONVERTER M-BUS-2 TRANSMITS THE FOLLOWING TYPES OF PACKETS
1.
Packet with current readings from connected heat meter, sent regularly or on request
Size in bytes
Field description
Data type
1 byte
Packet type, this packet = 1
uint8
1 byte
Battery level, %
uint8
1 byte
Values of basic settings (bit field)
uint8
4 bytes
Meter secondary address
uint32
4 bytes
Time of readings in this packet (unixtime UTC), by the internal
clock of the converter
uint32
4 bytes
The amount of thermal energy consumed, Wh
uint32
4 bytes
Total volume of coolant, l
uint32
4 bytes
Operating time, h
uint32
2 bytes
Current flow temperature ⁰С*100
uint16
2 bytes
Current temperature in the return line ⁰С*100
uint16
2 bytes
Current flow of coolant,
l
/h
uint16
The converter has internal clock and calendar; time and date is factory set. When sending
a packet with the current readings, the device uses the data taken at the nearest time, which is
multiple to the interval, set by the switches:
•
1 hour period: the readings of the beginning of the current hour are sent;
•
6 hours period: 00:00, 06:00, 12:00, 18:00 readings are sent;
•
12 hours period: 00:00, 12:00 readings are sent;
•
24 hours period: the readings of 00:00 of the current day are sent.
When transmitting on request the readings are taken in that moment.
A package of this type is transmitted separately for each connected meter. For example,
if 5 metering devices are connected to the converter, 5 packets will be transferred to the next
connection.
"Values of basic settings" bit field decoding
Bits
Field description
0 bit
Activation type 0 - OTAA, 1 – ABP
1 bit
Query for packet confirmation 0 – off, 1 – on
2,3,4 bit
Communication period:
