amrscm2mqtt

#!/usr/bin/env python3
'''
Runs rtlamr to watch for SDM broadcasts from utility meters. If the meter id
is in the list, usage is sent to an MQTT broker under a
'meters/{meter id}/reading' topic. All required settings should be specified in
settings.py.

'''
import backoff
import os
import paho.mqtt.client as mqtt
import settings
import signal
import ssl
import subprocess
import sys
import time

# Use signal to shut down gracefully
def shutdown(signum, frame):
	print('shutting down')
	rtlamr.terminate()

@backoff.on_exception(
	backoff.expo,
	(ConnectionRefusedError, ssl.SSLEOFError),
	max_time=300)
def try_reconnect(client):
	print('attempting to reconnect to broker...')
	client.reconnect()
	print('reconnected successfully')

signal.signal(signal.SIGTERM, shutdown)

# Start the rtl_tcp program
with subprocess.Popen([settings.RTL_TCP + " > /dev/null 2>&1 &"], shell=True, stdin=None, stdout=None, stderr=None, close_fds=True):
	time.sleep(10)
	print('started rtl_tcp')

	# Start the rtlamr program
	filter_ids = ','.join(map(str, settings.WATCHED_METERS))
	rtlamr_cmd = [settings.RTLAMR, '-msgtype=scm', '-format=csv', '-filterid=' + filter_ids, '-symbollength=' + str(settings.SYMBOL_LENGTH)]
	with subprocess.Popen(rtlamr_cmd, stdout=subprocess.PIPE, universal_newlines=True) as rtlamr:
		print('started rtlamr')

		# Configure the MQTT client
		client = mqtt.Client('rtlamr')
		if settings.MQTT_TLS:
			client.tls_set()
		if len(settings.MQTT_USER) and len(settings.MQTT_PASSWORD):
			client.username_pw_set(settings.MQTT_USER, settings.MQTT_PASSWORD)
		client.will_set('meters/availability', 'offline', retain=True)

		# Connect to the broker
		print('connecting to the broker...')
		client.connect(settings.MQTT_HOST, settings.MQTT_PORT)
		client.loop_start()
		client.publish('meters/availability', 'online', retain=True)
		print('connected successfully')

		# Process messages in a loop
		try:
			last_readings = {}
			for line in rtlamr.stdout:
				fields = line.strip().split(',')

				# Valid SCM results have 9 fields
				if len(fields) != 9:
					continue

				# Parse the results
				meter_id = int(fields[3])
				reading = int(fields[7])

				# Don't send a reading if the value hasn't changed
				if meter_id in last_readings.keys() and reading == last_readings[meter_id]:
					continue

				print('sending meter {} reading: {}'.format(meter_id, reading))

				result = client.publish('meters/{}/reading'.format(meter_id), reading, retain=True)
				if result.rc == mqtt.MQTT_ERR_SUCCESS:
					last_readings[meter_id] = reading
				elif result.rc == mqtt.MQTT_ERR_NO_CONN:
					try_reconnect(client)

				# If the broker restarted, LWT may have taken effect and marked us as offline
				client.publish('meters/availability', 'online', retain=True)
		except:
			print(sys.exc_info())
			raise
		finally:
                        # Clean up after rtlamr exits
                        print('disconnecting from broker...')
                        result = client.publish('meters/availability', 'offline', retain=True)
                        result.wait_for_publish()
                        client.disconnect()
                        client.loop_stop()