Dbstore Update Server Example

"""
Pymodbus Server With Updating Thread
--------------------------------------------------------------------------
This is an example of having a background thread updating the
context in an SQLite4 database while the server is operating.

This scrit generates a random address range (within 0 - 65000) and a random
value and stores it in a database. It then reads the same address to verify
that the process works as expected

This can also be done with a python thread::
    from threading import Thread
    thread = Thread(target=updating_writer, args=(context,))
    thread.start()
"""
# --------------------------------------------------------------------------- #
# import the modbus libraries we need
# --------------------------------------------------------------------------- #
from pymodbus.version import version
from pymodbus.server.asynchronous import StartTcpServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSequentialDataBlock
from pymodbus.datastore import ModbusServerContext
from pymodbus.datastore.database import SqlSlaveContext
from pymodbus.transaction import ModbusRtuFramer, ModbusAsciiFramer
import random

# --------------------------------------------------------------------------- #
# import the twisted libraries we need
# --------------------------------------------------------------------------- #
from twisted.internet.task import LoopingCall

# --------------------------------------------------------------------------- #
# configure the service logging
# --------------------------------------------------------------------------- #
import logging
logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

# --------------------------------------------------------------------------- #
# define your callback process
# --------------------------------------------------------------------------- #


def updating_writer(a):
    """ A worker process that runs every so often and
    updates live values of the context which resides in an SQLite3 database.
    It should be noted that there is a race condition for the update.
    :param arguments: The input arguments to the call
    """
    log.debug("Updating the database context")
    context  = a[0]
    readfunction = 0x03 # read holding registers
    writefunction = 0x10
    slave_id = 0x01 # slave address
    count = 50

    # import pdb; pdb.set_trace()

    rand_value = random.randint(0, 9999)
    rand_addr = random.randint(0, 65000)
    log.debug("Writing to datastore: {}, {}".format(rand_addr, rand_value))
    # import pdb; pdb.set_trace()
    context[slave_id].setValues(writefunction, rand_addr, [rand_value],
                                update=False)
    values = context[slave_id].getValues(readfunction, rand_addr, count)
    log.debug("Values from datastore: " + str(values))


def run_dbstore_update_server():
    # ----------------------------------------------------------------------- #
    # initialize your data store
    # ----------------------------------------------------------------------- #

    block = ModbusSequentialDataBlock(0x00, [0] * 0xff)
    store = SqlSlaveContext(block)

    context = ModbusServerContext(slaves={1: store}, single=False)

    # ----------------------------------------------------------------------- #
    # initialize the server information
    # ----------------------------------------------------------------------- #
    identity = ModbusDeviceIdentification()
    identity.VendorName = 'pymodbus'
    identity.ProductCode = 'PM'
    identity.VendorUrl = 'http://github.com/riptideio/pymodbus/'
    identity.ProductName = 'pymodbus Server'
    identity.ModelName = 'pymodbus Server'
    identity.MajorMinorRevision = version.short()

    # ----------------------------------------------------------------------- #
    # run the server you want
    # ----------------------------------------------------------------------- #
    time = 5  # 5 seconds delay
    loop = LoopingCall(f=updating_writer, a=(context,))
    loop.start(time, now=False)  # initially delay by time
    loop.stop()
    StartTcpServer(context, identity=identity, address=("", 5020))


if __name__ == "__main__":
    run_dbstore_update_server()