modbus_rtu_test.py

'''
Test script for interacting with device over modbus-rtc.
Need to improve received strings to output correctly after decoding.
'''

import pymodbus
import serial
from pymodbus.constants import Endian
from pymodbus.pdu import ModbusRequest
from pymodbus.client.sync import ModbusSerialClient as ModbusClient #initialize a serial RTU client instance
from pymodbus.transaction import ModbusRtuFramer
import logging
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.payload import BinaryPayloadBuilder
import hexdump

logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)
#usb_device = '/dev/tty.wchusbserial1420'
usb_device = '/dev/tty.usbserial-AL00KDH2'

#count= the number of registers to read
#unit= the slave unit this request is targeting
#address= the starting address to read from

client= ModbusClient(method = "rtu", port=usb_device,stopbits = 1, bytesize = 8, parity = 'N', baudrate= 9600, timeout=3, reconnects=2)

#Connect to the serial modbus server
connection = client.connect()
print connection

reg = 101
num_of_reg = 8
#Starting add, num of reg to read, slave unit.
result  = client.read_input_registers(reg, num_of_reg, unit=0x18) # address, count, slave address
if result and hasattr(result, 'registers'):
    decoder = BinaryPayloadDecoder.fromRegisters(result.registers, endian=Endian.Little)
    decoded = {
        'raw': result.registers,
        'string8': decoder.decode_string(8),
        'string16': decoder.decode_string(16),
        'string32': decoder.decode_string(32),
#        'float': decoder.decode_32bit_float(),
#        '16uint': decoder.decode_16bit_uint(),
#        '8int': decoder.decode_8bit_int(),
#        'bits': decoder.decode_bits(),
    }

    print "-" * 60
    print "Decoded Data"
    print "-" * 60
    for name, value in decoded.iteritems():
        print ("%s\t" % name), value