Send 1-wire temperature values from a Raspberry Pi to an MQTT broker

publish_temps.py

from __future__ import print_function

import os
import time

import paho.mqtt.client as mqtt
from paho.mqtt.client import MQTT_ERR_SUCCESS, MQTT_ERR_NO_CONN


DEVICES_PATH = "/sys/bus/w1/devices"
MQTT_HOST = "localhost"
MQTT_PORT = 1883
SLEEP_TIME = 30


def connect_mqtt():
    mqttc = mqtt.Client()
    print("Connecting to {}".format(MQTT_HOST))
    mqttc.connect(MQTT_HOST, MQTT_PORT, 60)
    print("Connected")
    mqttc.loop_start()
    mqttc.on_disconnect = on_disconnect
    return mqttc


def disconnect_mqtt(mqttc):
    mqttc.loop_stop()
    mqttc.disconnect()


def on_disconnect(client, userdata, rc):
    if rc != 0:
        print("Unexpected disconnection.")
        client.reconnect()


def get_thermometer_names():
    thermometers = [x[1] for x in os.walk(DEVICES_PATH)][0]
    while "w1_bus_master1" in thermometers: thermometers.remove("w1_bus_master1")
    return thermometers


def get_thermometer_temp(thermometer):
    with open("{}/{}/w1_slave".format(DEVICES_PATH, thermometer), "r") as tfile:
        text = tfile.read()
        secondline = text.split("\n")[1]
        temperaturedata = secondline.split(" ")[9]
        temperature = float(temperaturedata[2:])
        temperature = temperature / 1000
        return temperature


def publish_temp(mqttc, thermometer, temp):
    topic = "raspberry-pi/w1/thermometer/{}".format(thermometer)
    (result, mid) = mqttc.publish(topic, temp)
    if result == MQTT_ERR_SUCCESS:
        print("Published {} to {}".format(temp, topic))
    elif result == MQTT_ERR_NO_CONN:
        print("Connection error")
    else:
        print("Unknown error")


def main():
    print("Starting")
    try:
        mqttc = connect_mqtt()
        thermometers = get_thermometer_names()
        print("Detected {} thermometers".format(len(thermometers)))
        while True:
            for thermometer in thermometers:
                temp = get_thermometer_temp(thermometer)
                publish_temp(mqttc, thermometer, temp)
            time.sleep(SLEEP_TIME)
    except KeyboardInterrupt:
        print("Exiting")
    finally:
        print("Disconnecting from {}".format(MQTT_HOST))
        disconnect_mqtt(mqttc)
        print("Done")


if __name__ == "__main__":
    main()