Linuxcnc pymodbus example for remote I/O module

#MODBUS this section must be above everything in your code.
from __future__ import division
#/MODBUS


#MODBUS
import pymodbus
import serial
from pymodbus.pdu import ModbusRequest
from pymodbus.client.sync import ModbusSerialClient as ModbusClient #initialize a serial RTU client instance
from pymodbus.transaction import ModbusRtuFramer
from pymodbus.constants import Endian              # Nodig voor 32-bit float getallen (2 registers / 4 bytes)
from pymodbus.payload import BinaryPayloadDecoder  # Nodig voor 32-bit float getallen (2 registers / 4 bytes)
from pymodbus.payload import BinaryPayloadBuilder  # Nodig om 32-bit floats te schrijven naar register
from pymodbus.payload import BinaryPayloadBuilder, BinaryPayloadDecoder

method = "rtu"
port = "/dev/ttyUSB0"
baudrate = 9600
stopbits = 1
bytesize = 8
parity = "N"
timeout = 0.01
retries = 2
 
client = ModbusClient(method = method, port = port, stopbits = stopbits, bytesize = bytesize, parity = parity, baudrate = baudrate, timeout = timeout, retries = retries)
#connection = client.connect()
#/MODBUS


#Glade button example 

  def on_modbus_tool_pressed(self, widget, data=None):
    connection = client.connect()
    print connection
    y = 10  #10 volt
    client.write_register(0, float(4095 / 10) * y, unit=1)
    client.close()
    
    connection = client.connect()
    print connection
    b = 8  #8 volt
    client.write_register(1, float(4095 / 10) * b, unit=1)
    client.close()

    connection = client.connect()
    print connection
    client.write_coil(0, True)
    client.write_coil(1, True)
    client.write_coil(2, True)
    client.write_coil(3, True)
    client.close()

    connection = client.connect()
    print connection
    client.write_coil(0, False)
    client.write_coil(1, False)
    client.write_coil(2, False)
    client.write_coil(3, False)
    client.close()

    connection = client.connect()
    print connection
    analog_input = client.read_input_registers(0, 4, unit=1) 
    print data 
    print "value_0:", analog_input.registers[0]
    print "value_1:", analog_input.registers[1]
    print "value_2:", analog_input.registers[2]
    print "value_3:", analog_input.registers[3]
    client.close()

    connection = client.connect()
    print connection
    digital_input = client.read_discrete_inputs(0, 4, unit=1) 
    print data 
    print "value_0:", digital_input.bits[0]
    print "value_1:", digital_input.bits[1]
    print "value_2:", digital_input.bits[2]
    print "value_3:", digital_input.bits[3]
    client.close()