1 Introduction
This document describes features, parameters and setting possibilities of the WM868-MS-LP-H module, which
is used for transparent data transfer among remote segments of virtual bus through the WACO radio-frequency
network.
1.1 WACO communication system
WACO (Wireless Automatic Collector) is radio frequency (RF) communication system intended especially for the
remote reading of consumption meters (smart metering area), automatic data collection from sensors (telemetry
area), and bi-directional data transfer among control, sensing and actuating elements in automatic control systems
(industrial automation area). Installed WACO radio-frequency elements create local radio network covering object
of interest (flat, house, building, compound...) or required area (street, city...).
WACO RF network has a ”mesh” type of topology, where in reach of each radio element there could be placed
several other network elements that could operate also as repeaters of received signal. In this kind of network
there are typically several possible communication paths between the central point and other single elements of
the network. WACO network communication protocol was designed to provide a maximum data transmission
reliability and redundancy with using of multiple communication paths, but at the same time the network is
protected against circularity and multiplication of messages by sophisticated algorithms so that the network keeps
also a high performance even with high number of radio elements working in one network.
WACO communication protocol was designed in compliance with a telecommunication standard ISO/OSI model
that ensures a high variability of supported applications.
WACO radio-frequency devices (hereinafter ”radio modules”) are equipped with various types of input/output
interfaces that enables integration of various connected device (meters, sensors, actors...) into one network.
WACO communication system includes also special communication devices - WACO GateWays, that enable
receiving of radio messages from the local WACO RF-network and transfer them to the local or remote computer
through the serial line or Internet and (in inverse direction) receiving messages from the serial line/Internet and
broadcast them into ”its” RF-network.
1.2 Module usage
As it is clear from the functionality description below, the WM868-MS-LP-H module can be used in applications
of M-Bus/RS-485 data-bus systems, that are commonly deployed in industrial automation as well as in the area of
remote reading of meters and sensors (”metering”, ”smart metering”). The WM868-MS-LP-H module serves for
data transfer between the WACO RF-network and bus control unit (”M-Bus Master”), connected to the module’s
local M-Bus two-wire bus. Principle of module usage in a M-Bus data-bus system is shown in the figure 1.
As evident from the picture, the WM868-MS-LP-H module is connected to the main segment of WACO virtual
bus, where ”Master” of the bus is located. Remote segments of the virtual bus are equipped with WM868-MM
and WM868-R4 RF-modules (WM868-IR can be also used). The module receives messages (”requests”) from bus
control unit (”M-Bus Master”) through the wired bus and resend these requests into the WACO RF-network.
Remote WACO RF-modules receive the requests from RF network and resend them into their local (wired) buses.
Individual meters/sensors on the remote segments respond to the requests through the wired bus and ”their” WACO
RF-modules resend the responses to the WACO RF network. The WM868-MS-LP-H module on the main segment
receives the responses from RF network and resends them to the bus control unit (master) through the wired bus.
Data transfer is going on in the ”Virtual BUS” application (port ”32” in WACO network protocol), where the data
messages are transferred totally transparently, without any conversion. Even it is possible to interconnect several
remote bus segments with different physical type (e.g. M-Bus and RS-485 types, as depicted in the figure 1), all
devices (”Master” as well as all ”Slaves”) on the united virtual bus must use same communication protocol (same
data structure) to ”understand” each other. In metering area there are commonly used M-Bus and IEC 62056
(formerly DLMS) protocols, frequently used data protocols in industrial automation are Modbus, S-bus and similar
data formats.
The WM868-MS-LP-H module can be used only if bus control unit (M-Bus Master) is furnished for working on
the physical bus of M-Bus type. ”Slave” devices installed on the remote bus-segments (connected through the
WACO RF-network) are accessible for ”Master” device same way, as local devices (that are on the same segment
as ”Master”). From the logical structure point of view all physical segments are united together into the one large
data-bus as depicted in the lower part of the figure 1.
WM868-MS-LP-H 1
