KrystianD/modbus_client

Modbus client for Python

Device oriented Modbus client. As opposed to bare modbus clients, it focuses on data meaning and data types. Uses pymodbus under the hood.

Supported data types:

S16 (int16) - 16bit signed integer
U16 (uint16) - 16bit unsigned integer
S32BE (int32be) - 32bit signed integer, high word first
S32LE (int32le) - 32bit signed integer, low word first
U32BE (uint32be) - 32bit unsigned integer, high word first
U32LE (uint32le) - 32bit unsigned integer, low word first
S64BE (int64be) - 64bit signed integer, high word first
S64LE (int64le) - 64bit signed integer, low word first
U64BE (uint64be) - 64bit unsigned integer, high word first
U64LE (uint64le) - 64bit unsigned integer, low word first
F32BE (float32be) - IEEE 754 32bit float, high word first
F32LE (float32le) - IEEE 754 32bit float, low word first

Within the word, it assumes data is stored Least Significant Bit first.

Installation

pip install git+https://github.com/KrystianD/modbus_client

Example

Take an example energy meter device with 2 registers:

0x0001 - voltage, 1 word (2 bytes), LSB = 0.1 V
0x0002 - energy, 2 words (4 bytes), high word first, LSB = 1 Wh

===================
| Address | Value |
===================
|  0x0001 |   123 |
|  0x0002 |     1 |
|  0x0003 |    50 |
===================

config.yaml file content

zero_mode: True # if true, "address: 1" means second register, otherwise, "address: 1" means first register

registers:
  input_registers:
    - name: voltage
      address: 0x0001
      type: uint16
      scale: 0.1
      unit: V

    - name: energy
      address: 0x0002
      type: uint32be
      unit: Wh

    # or in short form:
    # - voltage/0x0001/uint16*0.1[V]
    # - energy/0x0002/uint32be[Wh]

Library usage

import asyncio
from modbus_client.client.pymodbus_async_modbus_client import PyAsyncModbusTcpClient
from modbus_client.device.modbus_device import ModbusDevice


async def main():
    modbus_client = PyAsyncModbusTcpClient(host="192.168.1.10", port=4444, timeout=3)
    # modbus_client = PyAsyncModbusRtuClient(path="/dev/ttyUSB0", baudrate=9600, stopbits=1, parity='N', timeout=3)
    modbus_device = ModbusDevice.create_from_file("config.yaml")
    voltage = await modbus_device.read_register(modbus_client, unit=1, register="voltage")
    energy = await modbus_device.read_register(modbus_client, unit=1, register="energy")
    print(voltage)  # 12.3
    print(energy)  # 65586


asyncio.get_event_loop().run_until_complete(main())

CLI usage:

python -m cli device config.yaml <connection-params> --unit 1 read voltage
python -m cli device config.yaml <connection-params> --unit 1 read energy

Features

Merging read requests
System config file support (storing devices addresses/paths and their unit numbers in config file for easy querying)

KrystianD / modbus_client