SOFTLINK WB169-RFG, Manual

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Figure 11: NEP Table of variables
To enable decoding of individual variables, there are two decoding information (
”
Type” and
”
Length”) that are
transferred with each variable. This way the receiving system can correctly find out OID, index and value of the
variable even without knowing its meaning. The general format of the data content of the message is shown in
figure
12 .
Figure 12: General structure of NEP variable
As it is clear from the figure, the UDP packet payload of one or more NEP variables, arranged in series. The general
structure of the NEP variable is shown at the bottom of the figure
12 .
Each Wireless M-Bus radio message is transported through the IP/UDP uplink in following three NEP-variables:
•
The first variable is
”
Message type” (OID 63). It is a mandatory NEP protocol variable that indicates
what type of message it is. The value of the variable carrying WMBUS data is always ”6”, which means ”
DATA ”. This variable always takes the same length in the UDP payload and is always the same.
•
The second variable is
”
RSSI” (OID 216/1). It is a number expressing the received signal strength (Received
Signal Strength Indication) with which the radio packet was received by the gateway. This variable is attached
to the Wireless M-Bus packet by gateway as potentially useful information for target application.
• The third variable is the Wireless M-Bus radio packet (OID 215/1) itself. Its length depends on the
number and type of transmitted M-Bus variables.
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