title: What is difference between pymodbus and pymodbus3 modules?
body: <p>Hope you are doing great! I recently started using python for modbus communication. I want to clear my few doubts.</p>
  
  <ol>
  <li>What module is better for modbus implementation using Python - minimalmodbus, pymodbus, pymodbus3 or else.</li>
  <li><strong>I am using python3.4</strong> but unable to install pymodbus module using pip or any means. So <strong>I installed pymodbus3</strong>.</li>
  <li><p>While using pymodbus3 module, I was able to write coils using following code:</p>
  
  <pre><code>import pymodbus3
  import serial
  from pymodbus3.pdu import ModbusRequest
  from pymodbus3.client.sync import ModbusSerialClient as ModbusClient 
  from pymodbus3.transaction import ModbusRtuFramer
  from serial.tools.list_ports import comports
  
  client = ModbusClient(method = "rtu", port = 'COM4',stopbits = 1, bytesize = 8, parity = 'N', baudrate= 19200)
  connection = client.connect()
  client.write_coil(1000, 1, unit = 0x01)
  </code></pre></li>
  </ol>
  
  <p>For reading coil status (function 0x01):</p>
  
  <pre><code>result = client.read_coils(1000,1)
  print(result)
  client.close()
  </code></pre>
  
  <p>Its returning None.   </p>
  
  <p>Or writing to register and reading is also not working:</p>
  
  <pre><code>client.write_register(0, 1000, unit=0x01)
  resu= client.read_holding_registers(0, 1, unit=0x01)
  print(resu)
  client.close()
  </code></pre>
  
  <p><em>Positive response is welcomed!</em></p>