danfoss-modbus-mqtt.py

#!/usr/bin/python

# Read temperature from Danfoss EKC202 and publish it on MQTT.
# Eirik Haustveit, 2016

import serial
import time

import crc16
import struct
import paho.mqtt.client as mqtt


ser = serial.Serial('/dev/danfoss', 9600, timeout=1, rtscts=False)

ser.bytesize = serial.EIGHTBITS #number of bits per bytes
ser.parity = serial.PARITY_EVEN #set parity check: no parity
ser.stopbits = serial.STOPBITS_ONE #number of stop bits
ser.xonxoff = False    #disable software flow control
ser.rtscts = False    #disable hardware (RTS/CTS) flow control
ser.dsrdtr = False       #disable hardware (DSR/DTR) flow control
ser.writeTimeout = 0.1 #timeout for write
ser.readTimeout = 0.1

#print ser

#address = '\x09'
#command = '\x11'
#
#data = address + command
#data = data + compute_crc(data)
#
#print('Transmitting: ' + str(data))
#ser.rts = True
#
#ser.dtr = True
#time.sleep(0.1)
#ser.write(data)
#
#ser.write(':010310010001EA\r\n')
#print repr(ser.read(1000)) # Read 1000 bytes, or wait for timeout


def read_input_register(dev, reg):
    command = chr(dev) + '\x04' + struct.pack('>H',reg) + '\x00\x01'
    crc =  crc16.calcString(command, 0xFFFF)
    command = command + struct.pack('<H',crc) 

    #print 'Register: ' +  str(reg)
    #print ":".join("{:02x}".format(ord(c)) for c in command)
    
    ser.rts = True
    ser.write(command)
    time.sleep(0.008)
    ser.rts = False

    time.sleep(1)        
 
    response = ser.readline()


    #TODO: Implement check of checksum(CRC), and handle any modbus error messages
    #checksum = ord(response[5:7])
    #comp_checksum = struct.pack('<H',crc16.calcString(response[1:5], 0xFFFF))
    #print 'chk: ' + str(comp_checksum) 
    return response 
  
def main():

    mqttc = mqtt.Client()

    mqttc.connect("localhost")
    mqttc.loop_start()

 #   while True:

    response = read_input_register(1, 2575)

    if response:    
        print ":".join("{:02x}".format(ord(c)) for c in response)
    
        temperature = ord(response[4:5])/10.0
        print 'Temperature: ' + str(temperature)
        mqttc.publish("ekc2021/temperature", temperature) 
    else:
        print "No data for EKC module at address 1"
 
    response = read_input_register(2, 2575)
    
    if response: 
        temperature = ord(response[4:5])/10.0
        print 'Temperature: ' + str(temperature)
        mqttc.publish("ekc2022/temperature", temperature)
    else:
        print "No data for EKC module at address 2"
 
#        time.sleep(2)

if __name__ == '__main__':
    main()