I have been trying to use pymodbus to read registers from a power meter and searching around here I found a useful code from the question I attach in the end of this post. So I wrote/copied the next code:

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

#def checkProxCounter():
count = 0
result = 0

client = ModbusClient(method='rtu',port='/dev/ttyUSB0',parity='N',stopbits=1,bytesize=8,baudrate=9600,timeout=3)

  if client.connect():
  print ("Port open")
  result = client.read_holding_registers(address=0x00, count=2,unit=0x01)
  print ("Result : ")
  print (result)
  blah = client.read_discrete_inputs(1,8)

  if blah != None:
      print("{}: {}".format("Blah", blah.bits[0]))

  if result != None:
      count = int(str(result.registers[0]),16) + int(str(result.registers[1]),16)
      print("{}: {}".format("Count", count))
      print("results were none")
  print("Port failed to open")
  count = -2

  print("Unknown Exception")

print count

When I try to run it the next Output appears:

Port Open
Unknown Exception
Traceback(most recent call last):
  File"prueba2.py", line 30, in <module>
    count = int(str(result.registers[0]),16) + int(str(result.registers[1]),16)
AttributeError:'ReadHoldingRegistersResponse' object has no attribute 'register'

Obviously there is something wrong or missing here but I am still a beginner programming and I don't see it. I understand that the variable "count" is changing the register to an integer. And to be honest I don't know what is exactly doing the variable "blah" nor the code printed as "{}: {}".format( ) .

Any advice or way to fix this problem?

Error in reading data with pymodbus

1 Answer 1


Turns out that by adding print result.registers, I could obtain the data.

  • Please accept your own answer with a click on the tick on its left side. Only this will finish the question and it will not pop up again year for year.
    – Ingo
    Jan 4, 2020 at 17:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.