Accessing MQTT Devices

Installing paho-mqtt library

!pip install paho-mqtt

Requirement already satisfied: paho-mqtt in /usr/local/lib/python3.6/dist-packages (1.5.1)

Particle Argon

The following code is flashed to the Particle Argon using the Particle Web IDE.

// Report temperature and humidity sensor. Provide a short blink of D7
// to indicate an temperture/humidity update.

#include <Grove_Temperature_And_Humidity_Sensor.h>
#include <MQTT.h>

int led = D7;
DHT dht(D2);

float temp, humidity;

void callback(char* topic, byte* payload, unsigned int length);
MQTT client("mqtt.eclipse.org", 1883, callback);

// receive message
void callback(char* topic, byte* payload, unsigned int length) {
}

void setup() {
    
    dht.begin();
    pinMode(led, OUTPUT);
    client.connect("argon_" + String(Time.now()));
}

void loop() {
    
    temp = dht.getTempFarenheit();
    humidity = dht.getHumidity();
    
    client.publish("cbe-virtual-laboratory/devices/argon", Time.timeStr() + ", " + String(temp, 1) + ", " + String(humidity, 1));
    
    digitalWrite(led, HIGH);
    delay(200);
    digitalWrite(led, LOW);
    delay(4800);
}

Receiving data from Particle Argon device

import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
import time

# select experiment duration
broker = "mqtt.eclipse.org"
topic = "cbe-virtual-laboratory/devices/#"
duration = 30

# callback after completing connection
def on_connect(client, userdata, flags, rc):
    print(f"Connected to {broker} with result code {rc}")
    client.subscribe(topic)

# callback after receiving a message
def on_message(client, userdata, msg):
    print(f"{msg.topic}: {msg.payload.decode('utf-8')}")

# create and setup MQTT client
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(broker, 1883, 60)

# listen for measurement information
client.loop_start()
time.sleep(duration)
client.loop_stop()

Connected to mqtt.eclipse.org with result code 0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:50:42 2020, 71.6, 47.0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:50:47 2020, 0.0, 47.0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:50:52 2020, 71.6, 47.0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:50:58 2020, 0.0, 47.0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:51:03 2020, 71.6, 47.0
cbe-virtual-laboratory/devices/argon: Fri Oct  9 12:51:08 2020, 71.6, 47.0