Modbus Read/Write Plugins for Domoticz

Author: Sebastiaan Ebeltjes / DomoticX.nl

Succesfully Tested on Domoticz version: 2020.2 stable

You can update domoticz with command: cd /home/pi/domoticz | ./updaterelease

Support for:

• RTU
• ASCII
• RTU over TCP
• TCP/IP

Functions of the READ plugin

• Read Coil (Function 1)
• Read Discrete Input (Function 2)
• Read Holding Registers (Function 3)
• Read Input Registers (Function 4)

Supported data types:

• No conversion (passtrough)
• BOOL (TRUE/FALSE)
• INT 8/16/32/64-Bit
• UINT 8/16/32/64-Bit
• FLOAT 32/64-Bit
• STRING 2/4/6/8 Bytes

Functions of the WRITE plugin

• Write Single Coil (Function 5)
• Write Single Holding Register (Function 6)
• Write Multiple Coils (Function 15)
• Write Registers (Function 16)

RTU/ASCII/RTU over TCP: Write HEX Payloads, like: 0x0100 TCP/IP: Write INT Payloads, like: 53

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Installation

Place the folders inside the domoticz plugin folder, for example like this construction:

/home/pi/domoticz/plugins/modbus-write/plugin.py

/home/pi/domoticz/plugins/modbus-read/plugin.py

Then restart domoticz with: sudo service domoticz.sh restart

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Using RTU / ASCII (SERIAL HW)

• Hardware: USB RS485-Serial Stick like This one
• Setup: Select method "RTU" or "ASCII", Serial Port, BaudRate, PortSettings
• Device adress is most likely: 1 to 247
• Payload in HEX, like: 0x0100

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Using RTU over TCP / TCP/IP

• Hardware: Not required
• Setup: Select method "RTU over TCP" or "TCP/IP"
• Device adress is most likely an ip: xxx.xxx.xxx.xxx
• Port is default 502
• RTU over TCP: Write HEX Payloads, like: 0x0100
• TCP/IP: Write INT Payloads, like: 53

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Dependancies

1. RPi: Raspbian image (FULL version recommended)
2. additional python3 libraries:

pymodbus AND pymodbusTCP

Install with: sudo pip3 install -U pymodbus pymodbusTCP

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HW Tested:

• Relay board
• KWh Meter - EASTRON SDM120
• Temp/Hum sensor - XY-MD01 or XY-MD02