====Write Values to an Modbus/TCP Slave Device====

===Description===

This script sets a value inside a Modbus/TCP slave device. 

This is used if you want to link the form system back into your control or information systems to advise that that a job - such as an isolation - has been completed.

In turn, you could use this to indicate isolation in SCADA, route around the isolated equipment in your plant logic, or simply keep a history of events in your historian product without having to add additional data sources.

In the example below, the target Modbus address to be set is a //property of the asset//. We read the target address from the ARDI API before we set it.

We also set a fixed value (in this case, **1**) to the address. Alternatively, you could set timestamps, strings etc. 

===Full Script===

<code Python>
import requests
import pymodbus
from datetime import datetime
import os
import sys
import traceback
import warnings
from pymodbus.client.sync import ModbusTcpClient

#Set default details

#The ARDI server to query
server="localhost/s/bm"

#The ARDI property containing the Modbus address
mbaddressid=47

#Modbus connection details
ipaddress="localhost"
unit=1
port=502
register=0
offset=0

#The value to write
valuetoset=1

asset = "Unknown Asset"
checklist = "Unknown Checklist"
user = "Unknown User"
assetid = "1"
tm = datetime.now().strftime("%Y/%m/%d %H:%M:%S")

#Get submission details from environment variables
try:
    asset = os.environ["assetname"]
except:
    print "No Asset Provided"
    sys.exit(0)

try:
    assetid = os.environ["assetid"]
except:
    print "No Asset ID Provided"
    sys.exit(0)
    
try:
    checklist = os.environ["checklist"]
except:
    print "No Checklist Provided"
    sys.exit(0)

try:
    user = os.environ["user"]
except:
    print "No User Provided"
    sys.exit(0)

def Sub(st,ass,chk,usr,dt):
    return st.replace("{checklist}",chk).replace("{asset}",ass).replace("{user}",usr).replace("{date}",dt)

#Get isolation modbus address from server (assumes a Guest Mode server, otherwise we need to authenticate!)
url = "http://" + server + "/api/asset/property?id=" + str(assetid) + "&property=" + str(mbaddressid)
resp = requests.get(url)

data = resp.content


#Read the address from ARDI
ind = data.find("<text>")
if ind > 0:
    indx = data.find("</text>")
    totaloffset = ind + 6
    value = data[totaloffset:indx]

    #Adjust the value based on the type of I/O point we are talking about.
    if len(value) > 3:
        if value[0] == '1':
            register = 1
            offset = 1000
            if len(value) > 4:
                offset = 10000
        if value[0] == '3':
            register = 3
            offset = 3000
            if len(value) > 4:
                offset = 30000
        if value[0] == '4':
            register = 4
            offset = 4000
            if len(value) > 4:
                offset = 40000
    

    #Connect to modbus device
    client=ModbusTcpClient(ipaddress,port=port)
    client.connect()
    address = int(value)-offset
    
    #Write data at correct location...
    if register == 3:
        client.write_input_register(address,int(valuetoset),unit=unit)
    if register == 4:
        client.write_register(address,int(valuetoset),unit=unit)
    if register == 1:
        if valuetoset == 1:
            valuetoset = True
        else:
            valuetoset = False
        client.write_discrete_input(address,valuetoset,unit=unit)
    if register == 0:
        if valuetoset == 1:
            valuetoset = True
        else:
            valuetoset = False
        client.write_coil(address,valuetoset,unit=unit)
    
#If everything worked out, send the word 'OK'.
print 'OK'
</code>