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12. Modbus RTU/TCP interconnection with LM
Modbus RTU is supported over RS-485 ports. Modbus TCP is supported over Ethernet port.
Modbus communication is done either from visual Modbus mapper (only 1 RS485 interface can
be defined through visual mapper. If you need to configure another RS-485, use scripting) for
Modbus Master or through scripts for Modbus Slave.
Modbus Master user graphical mapper interface in Modbus tab
Modbus Slave to use LM as Modbus Slave, disable Modbus RTU in ModbusRTU settings,
and use scripts for the communication
12.1. Modbus device profile
First thing you should do is to define Modbus device profile it is a *.json file with the following
structure e.g. a fragment from UIO20 device by Embedded Systems:
{
"manufacturer": "Embedded Systems",
"description": "Universal 16+4 I/O module",
"mapping": [
{ "name": "Output 1", "bus_datatype": "bool", "type": "coil", "address": 0, "writable": 1 },
{ "name": "Input 1", "bus_datatype": "float16", "type": "inputregister", "address": 0, "value_multiplier": 0.001, "units": "V" }
]
}
Name Object name, e.g. Output 2 (String, Required)
Bus_datatype - KNX object data type, key from dt table, e.g. float32 (String/Number,
Required)
Type Modbus register type, possible values: coil discreteinput register inputregister
(String, Required)
Address Register address (0-based) (Number, Required)
Writable - Set to true to enable writing to register if type is either coil or register
(Boolean)
Datatype Modbus value data type. If set, conversion will be done automatically.
Possible values: uint16 int16 float16 uint32 int32 float32 uint64 int64 quad10k s10k
(String)
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