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read_modbus.py
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read_modbus.py
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#!/usr/bin/env python3
# MIT License
#
# Copyright (c) 2020 aattww (https://github.com/aattww/)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# Simple Python script to read data from a Sensors gateway. Use for debugging.
#
# Remember to change the correct port and slave address below before use.
# Also remember to install minimalmodbus library: https://pypi.org/project/minimalmodbus/
# Use with "read_modbus.py register_start nr_of_registers".
# For example,
# "read_modbus.py 0 20" will read all gateway data, while
# "read_modbus.py 100 8" will show data for node id 1.
##################
# BEGIN SETTINGS #
##################
# Serial settings
serial_device = "/dev/serial0" # This should work with Raspberry if gateway is connected directly to headers
modbus_address = 1 # Gateway slave address
################
# END SETTINGS #
################
import minimalmodbus
import sys
# Helper function to convert 16 bit unsigned values from gateway to signed 16 bit values
# so that negative values are handled correctly.
#
# value: unsigned value to be converted
#
# returns: signed value
#
def to_signed(value):
if (value >= 2**15):
return (value - 2**16)
else:
return (value)
gateway = minimalmodbus.Instrument(serial_device, modbus_address)
gateway.serial.baudrate = 38400
register_start = int(sys.argv[1])
registers_to_read = int(sys.argv[2])
# Read modbus data
try:
mb_data = gateway.read_registers(register_start, registers_to_read)
if len(mb_data) == registers_to_read:
print("Read Modbus data:")
print()
i = 0
for register in mb_data:
print("%i: %i" %(register_start + i, to_signed(register)))
i = i + 1
else:
print("Wrong number of registers read: %i instead of %i" %(len(mb_data), registers_to_read))
except Exception as e:
print("Error reading Modbus:")
print(e)