Custom Datablock Example

#!/usr/bin/env python
'''
Pymodbus Server With Custom Datablock Side Effect
--------------------------------------------------------------------------

This is an example of performing custom logic after a value has been
written to the datastore.
'''
#---------------------------------------------------------------------------# 
# import the modbus libraries we need
#---------------------------------------------------------------------------#
from __future__ import print_function
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

#---------------------------------------------------------------------------# 
# configure the service logging
#---------------------------------------------------------------------------# 

import logging
logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

#---------------------------------------------------------------------------# 
# create your custom data block here
#---------------------------------------------------------------------------# 

class CustomDataBlock(ModbusSparseDataBlock):
    ''' A datablock that stores the new value in memory
    and performs a custom action after it has been stored.
    '''

    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(ModbusSparseDataBlock, self).setValues(address, value)

        # whatever you want to do with the written value is done here,
        # however make sure not to do too much work here or it will
        # block the server, espectially if the server is being written
        # to very quickly
        print("wrote {} to {}".format(value, address))


#---------------------------------------------------------------------------# 
# initialize your data store
#---------------------------------------------------------------------------# 

block   = CustomDataBlock([0]*100)
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))