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uModbus
=======
uModbus or (μModbus) is a pure Python implementation of the Modbus protocol as
described in the `MODBUS Application Protocol Specification V1.1b3`_. uModbus
implements both a Modbus client (both TCP and RTU) and a Modbus server (both
TCP and RTU). The "u" or "μ" in the name comes from the the SI prefix "micro-".
uModbus is very small and lightweight. The source can be found on GitHub_.
Documentation is available at `Read the Docs`_.
Quickstart
----------
Creating a Modbus TCP server is easy:
..
Because GitHub doesn't support the include directive the source of
scripts/examples/simple_tcp_server.py has been copied to this file.
.. code:: python
#!/usr/bin/env python
# scripts/examples/simple_tcp_server.py
import logging
from socketserver import TCPServer
from collections import defaultdict
from umodbus import conf
from umodbus.server.tcp import RequestHandler, get_server
from umodbus.utils import log_to_stream
# Add stream handler to logger 'uModbus'.
log_to_stream(level=logging.DEBUG)
# A very simple data store which maps addresss against their values.
data_store = defaultdict(int)
# Enable values to be signed (default is False).
conf.SIGNED_VALUES = True
TCPServer.allow_reuse_address = True
app = get_server(TCPServer, ('localhost', 502), RequestHandler)
@app.route(slave_ids=[1], function_codes=[3, 4], addresses=list(range(0, 10)))
def read_data_store(slave_id, function_code, address):
"""" Return value of address. """
return data_store[address]
@app.route(slave_ids=[1], function_codes=[6, 16], addresses=list(range(0, 10)))
def write_data_store(slave_id, function_code, address, value):
"""" Set value for address. """
data_store[address] = value
if __name__ == '__main__':
try:
app.serve_forever()
finally:
app.shutdown()
app.server_close()
Doing a Modbus request requires even less code:
..
Because GitHub doesn't support the include directive the source of
scripts/examples/simple_data_store.py has been copied to this file.
.. code:: python
#!/usr/bin/env python
# scripts/examples/simple_tcp_client.py
import socket
from umodbus import conf
from umodbus.client import tcp
# Enable values to be signed (default is False).
conf.SIGNED_VALUES = True
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('localhost', 502))
# Returns a message or Application Data Unit (ADU) specific for doing
# Modbus TCP/IP.
message = tcp.write_multiple_coils(slave_id=1, starting_address=1, values=[1, 0, 1, 1])
# Response depends on Modbus function code. This particular returns the
# amount of coils written, in this case it is.
response = tcp.send_message(message, sock)
sock.close()
Features
--------
The following functions have been implemented for Modbus TCP and Modbus RTU:
* 01: Read Coils
* 02: Read Discrete Inputs
* 03: Read Holding Registers
* 04: Read Input Registers
* 05: Write Single Coil
* 06: Write Single Register
* 15: Write Multiple Coils
* 16: Write Multiple Registers
Other featues:
* Support for signed and unsigned register values.
License
-------
uModbus software is licensed under `Mozilla Public License`_. © 2018 `Advanced
Climate Systems`_.
.. External References:
.. _Advanced Climate Systems: http://www.advancedclimate.nl/
.. _GitHub: https://github.com/AdvancedClimateSystems/uModbus/
.. _MODBUS Application Protocol Specification V1.1b3: http://modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf
.. _Mozilla Public License: https://github.com/AdvancedClimateSystems/uModbus/blob/develop/LICENSE
.. _Read the Docs: http://umodbus.readthedocs.org/en/latest/
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