gistfile1.py

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)
GPIO.cleanup()
# led pin setup
GPIO.setup(7, GPIO.OUT)
# button pin setup
GPIO.setup(12, GPIO.IN)

import mosquitto, json, time

# event callbacks
def on_connect(obj, rc):
    print('Connected, rc: ' + str(rc))

def on_message(obj, msg):
    json_data = msg.payload
    client.publish(out_topic, json_data)
    value = json.loads(json_data)['properties'][0]['value']
    if value == 'on':
        GPIO.output(7, GPIO.HIGH)
    else:
        GPIO.output(7, GPIO.LOW)

def on_subscribe(mosq, obj, mid):
    print('Subscribed: ' + str(mid))

# create client
client = mosquitto.Mosquitto('<CLIENT-ID>')

# assign event callbacks
client.on_message = on_message
client.on_connect = on_connect
client.on_subscribe = on_subscribe

# device credentials
device_id     = '<DEVICE-ID>'
device_secret = '<DEVICE-SECRET>'

# device topics
in_topic  = 'devices/' + device_id + '/get'  # receiving messages
out_topic = 'devices/' + device_id + '/set'  # publishing messages

# client connection
client.username_pw_set(device_id, device_secret)
client.connect('96.126.109.170')

# subscribe (with QoS level 0)
client.subscribe(in_topic, 0)

prev_status = GPIO.LOW
updated_at = 0  # the last time the output pin was toggled
debounce = 0.2  # the debounce time, increase if the output flickers

# Continue the network loop, exit when an error occurs
rc = 0
while rc == 0:
    rc = client.loop()
    button = GPIO.input(12)

    if button != prev_status and time.time() - updated_at > debounce:
        prev_status = button
        updated_at = time.time()

        button_payload = 'off'
        if button == GPIO.HIGH:
            button_payload = 'on'

        # effectively update the light status
        GPIO.output(7, button)
        payload = { 'properties': [{ 'id': '518be5a700045e1521000001', 'value': button_payload }] }
        client.publish(out_topic, json.dumps(payload))

print('rc: ' + str(rc))