pymodbus read meter registers

Question

I'm new to modbus but I have a small project to work on. I need to read some values from an energy meter. I wrote this from some examples found in the internet:

import logging
from pymodbus.client.sync import ModbusTcpClient as ModbusClient

logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

client = ModbusClient('192.168.80.210')
client.connect() 
rr = client.read_holding_registers(40012, 1)
print rr

client.close()

It seems to be connecting to the meter 'cause this is my output:

DEBUG:pymodbus.transaction:Current transaction state - IDLE
DEBUG:pymodbus.transaction:Running transaction 1
DEBUG:pymodbus.transaction:SEND: 0x0 0x1 0x0 0x0 0x0 0x6 0x0 0x3 0x9c 0x4c 0x0 0x1
DEBUG:pymodbus.client.sync:New Transaction state 'SENDING'
DEBUG:pymodbus.transaction:Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
DEBUG:pymodbus.transaction:Transaction failed. (Modbus Error: [Invalid Message] Incomplete message received, expected at least 8 bytes (0 received)) 
DEBUG:pymodbus.framer.socket_framer:Processing: 
DEBUG:pymodbus.transaction:Getting transaction 1
DEBUG:pymodbus.transaction:Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'
Modbus Error: [Input/Output] Modbus Error: [Invalid Message] Incomplete message received, expected at least 8 bytes (0 received)

I want to read from register 40012 to 40014 and this is Modbusdbus map I have: Modbus map

I appreciate your help. Regards,

Benyamin Jafari Benyamin Jafari · Accepted Answer · 2018-11-21T21:55:20

I think you should set the unit and port argument, and for getting the value use the rr.registers, so you need to know the unit_ID value, and the device port.

In most cases, the unit is 1 and the port is 502 as the modbus default.

If you want to read from address 40012 to 40014, you could read from 40012 as a bulky reading with count=3.

I improved your code, try it:

from pymodbus.client.sync import ModbusTcpClient

client = ModbusTcpClient('192.168.80.210', port=502)

if client.connect():
    res = client.read_holding_registers(40012, count=3, unit=1)

    if not res.isError():
    '''.isError() was implemented in pymodbus version 1.4.0 and above.'''
        print(res.registers)
    else:
        # handling error
        print(res)

client.close()

pymodbus read meter registers

1 Answers