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2019 Radiocrafts AS
MBUS User Manual (ver 2.01)
MBUS USER MANUAL
Frame format for transmitting data
The data frame for the UART RXD pin (input for transmitting a Wireless M-Bus packet) is built like this:
Figure 4
– UART interface packet transmission (RXD pin)
L is the length (not including the length byte itself), followed by the application data with the CI byte first. CI is the
Control Information byte. The application data typically contains the application header (transport layer), and data
points with VIF and DIF codes. The application data can also be SML or DMLS or manufacturer specific.
An Extended Link Layer (ELL) can be added before the application data using this structure:
L + CI
ELL
+ ELL + CI
APL
+ APPL_DATA
The HEADER and C-field (and adjusted L value) is added to the Wireless M-Bus packet automatically by the
module before transmitting over RF and both can be changed in configuration mode.
To transmit only a HEADER without Application data (CI+APPL_DATA) a L=0xFE can be sent to the module UART
without additional bytes.
Frame format when receiving data
The data frame for the UART TDX pin (Output for received Wireless M-Bus packets) is built like this:
Figure 5
– UART interface packet reception (TXD pin)
Data in blue and yellow are optional output parts of the UART message and can be enabled in configuration mode
by the DATA_INTERFACE and RSSI_MODE configuration parameters.
L is the length byte and is always present. It does not include itself or the START/STOP bytes, but will include
RSSI and CRC if enabled. CRC is calculated from length byte including RSSI (if enebled).
Note!
The length bytes itself must be reduced by 2 before calculating CRC on host. The length byte was
shorter at calculation in module as the CRC was not added at time of calculation.
CI
APPL_DATA
L
START
L
HEADER
APPL_DATA
RSSI
CRC
STOP
C
M_ID2
M_ID1
U_ID4
U_ID3
U_ID2
U_ID1
VER
DEV
CRC1
CRC2
L=Lenght of {C+CI+APRSSI+CRC}
Enable by RSSI_MODE
Enable by DATA_INTERFACE
Enable by DATA_INTERFACE
CI
