#!/usr/bin/env python
"""
Pymodbus Server With Callbacks
--------------------------------------------------------------------------
This is an example of adding callbacks to a running modbus server
when a value is written to it. In order for this to work, it needs
a device-mapping file.
"""
# --------------------------------------------------------------------------- #
# import the modbus libraries we need
# --------------------------------------------------------------------------- #
from pymodbus.server.async import StartTcpServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSparseDataBlock
from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
from pymodbus.transaction import ModbusRtuFramer, ModbusAsciiFramer
# --------------------------------------------------------------------------- #
# import the python libraries we need
# --------------------------------------------------------------------------- #
from multiprocessing import Queue, Process
# --------------------------------------------------------------------------- #
# configure the service logging
# --------------------------------------------------------------------------- #
import logging
logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)
# --------------------------------------------------------------------------- #
# create your custom data block with callbacks
# --------------------------------------------------------------------------- #
class CallbackDataBlock(ModbusSparseDataBlock):
""" A datablock that stores the new value in memory
and passes the operation to a message queue for further
processing.
"""
def __init__(self, devices, queue):
"""
"""
self.devices = devices
self.queue = queue
values = {k: 0 for k in devices.keys()}
values[0xbeef] = len(values) # the number of devices
super(CallbackDataBlock, self).__init__(values)
def setValues(self, address, value):
""" Sets the requested values of the datastore
:param address: The starting address
:param values: The new values to be set
"""
super(CallbackDataBlock, self).setValues(address, value)
self.queue.put((self.devices.get(address, None), value))
# --------------------------------------------------------------------------- #
# define your callback process
# --------------------------------------------------------------------------- #
def rescale_value(value):
""" Rescale the input value from the range
of 0..100 to -3200..3200.
:param value: The input value to scale
:returns: The rescaled value
"""
s = 1 if value >= 50 else -1
c = value if value < 50 else (value - 50)
return s * (c * 64)
def device_writer(queue):
""" A worker process that processes new messages
from a queue to write to device outputs
:param queue: The queue to get new messages from
"""
while True:
device, value = queue.get()
scaled = rescale_value(value[0])
log.debug("Write(%s) = %s" % (device, value))
if not device: continue
# do any logic here to update your devices
# --------------------------------------------------------------------------- #
# initialize your device map
# --------------------------------------------------------------------------- #
def read_device_map(path):
""" A helper method to read the device
path to address mapping from file::
0x0001,/dev/device1
0x0002,/dev/device2
:param path: The path to the input file
:returns: The input mapping file
"""
devices = {}
with open(path, 'r') as stream:
for line in stream:
piece = line.strip().split(',')
devices[int(piece[0], 16)] = piece[1]
return devices
def run_callback_server():
# ----------------------------------------------------------------------- #
# initialize your data store
# ----------------------------------------------------------------------- #
queue = Queue()
devices = read_device_map("device-mapping")
block = CallbackDataBlock(devices, queue)
store = ModbusSlaveContext(di=block, co=block, hr=block, ir=block)
context = ModbusServerContext(slaves=store, single=True)
# ----------------------------------------------------------------------- #
# initialize the server information
# ----------------------------------------------------------------------- #
identity = ModbusDeviceIdentification()
identity.VendorName = 'pymodbus'
identity.ProductCode = 'PM'
identity.VendorUrl = 'http://github.com/bashwork/pymodbus/'
identity.ProductName = 'pymodbus Server'
identity.ModelName = 'pymodbus Server'
identity.MajorMinorRevision = '1.0'
# ----------------------------------------------------------------------- #
# run the server you want
# ----------------------------------------------------------------------- #
p = Process(target=device_writer, args=(queue,))
p.start()
StartTcpServer(context, identity=identity, address=("localhost", 5020))
if __name__ == "__main__":
run_callback_server()