.. note:: Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts. **Why Join?** - **Expert Support**: Solve post-sale issues and technical challenges with help from our community and team. - **Learn & Share**: Exchange tips and tutorials to enhance your skills. - **Exclusive Previews**: Get early access to new product announcements and sneak peeks. - **Special Discounts**: Enjoy exclusive discounts on our newest products. - **Festive Promotions and Giveaways**: Take part in giveaways and holiday promotions. 👉 Ready to explore and create with us? Click [|link_sf_facebook|] and join today! .. _nt_mqtt_publish: 8.5 Cloud Calling System with @MQTT ============================================ Message Queuing Telemetry Transport (MQTT) is a simple messaging protocol. It is also the most common messaging protocol for the Internet of Things (IoT). MQTT protocols define the way IoT devices transfer data. They are event-driven and interconnected using the Pub/Sub model. The sender (Publisher) and the receiver (Subscriber) communicate via Topics. A device publishes a message on a specific topic, and all devices subscribed to that topic receive the message. In this section, a service bell system will be made using Pico W, HiveMQ (a free public MQTT broker service), and four buttons. The four buttons mean four tables in the restaurant, and you will be able to see which table's guests need service on HiveMQ when the customer presses the button. **1. Required Components** In this project, we need the following components. It's definitely convenient to buy a whole kit, here's the link: .. list-table:: :widths: 20 20 20 :header-rows: 1 * - Name - ITEMS IN THIS KIT - LINK * - Kepler Kit - 450+ - |link_kepler_kit| You can also buy them separately from the links below. .. list-table:: :widths: 5 20 5 20 :header-rows: 1 * - SN - COMPONENT - QUANTITY - LINK * - 1 - :ref:`cpn_pico_w` - 1 - |link_picow_buy| * - 2 - Micro USB Cable - 1 - * - 3 - :ref:`cpn_breadboard` - 1 - |link_breadboard_buy| * - 4 - :ref:`cpn_wire` - Several - |link_wires_buy| * - 5 - :ref:`cpn_resistor` - 4(10KΩ) - |link_resistor_buy| * - 6 - :ref:`cpn_button` - 4 - |link_button_buy| * - 7 - :ref:`cpn_lipo_charger` - 1 - * - 8 - 18650 Battery - 1 - * - 9 - Battery Holder - 1 - **2. Build the Circuit** .. warning:: Make sure your Li-po Charger Module is connected as shown in the diagram. Otherwise, a short circuit will likely damage your battery and circuitry. .. image:: img/wiring/5.mqtt_pub.png :width: 800 **3. Visit HiveMQ** HiveMQ is an MQTT broker and client-based messaging platform that enables fast, efficient and reliable data transfer to IoT devices.。 1. Open |link_hivemq| in your browser. 2. Connects the client to the default public proxy. .. image:: img/mqtt-1.png 3. Click on **Add New Topic Subscription**. .. image:: img/mqtt-2.png 4. Fill in the topics you want to follow and click **Subscribe**. The topics set here should be more personal to avoid getting messages from other users, and pay attention to case sensitive. .. image:: img/mqtt-3.png **4. Install the MQTT Module** Before we can start the project, we need to install the MQTT module for Pico W. 1. Connect to the network by running ``do_connect()`` in the Shell, which we wrote earlier. .. note:: * Type the following commands into the Shell and press ``Enter`` to run them. * If you don't have ``do_connect.py`` and ``secrets.py`` scripts in your Pico W, please refer to :ref:`iot_access` to create them. .. code-block:: python from do_connect import * do_connect() 2. After a successful network connection, import the ``mip`` module in the shell and use ``mip`` to install the ``umqtt.simple`` module, which is a simplified MQTT client for MicroPython. .. code-block:: python import mip mip.install('umqtt.simple') 3. You will see that the ``umqtt`` module is installed under the ``/lib/`` path of Pico W after completion. .. image:: img/5_calling_system1.png **5. Run the Script** #. Open the ``5_mqtt_publish.py`` file under the path of ``kepler-kit-main/iot``. #. Click the **Run current script** button or press F5 to run it. .. image:: img/5_calling_system2.png #. Go back to |link_hivemq| again and when you press one of the buttons on the breadboard, you will be able to see the Messages prompt on HiveMQ. .. image:: img/mqtt-4.png #. If you want this script to be able to boot up, you can save it to the Raspberry Pi Pico W as ``main.py``. **How it works?** The Raspberry Pi Pico W needs to be connected to the Internet, as described in :ref:`iot_access`. For this project, just use it. .. code-block:: python from do_connect import * do_connect() Initialize 4 button pins. .. code-block:: python sensor1 = Pin(16, Pin.IN) sensor2 = Pin(17, Pin.IN) sensor3 = Pin(18, Pin.IN) sensor4 = Pin(19, Pin.IN) Create two variables to store the ``URL`` and ``client ID`` of the MQTT broker we will use to connect to it. Since we are using a public broker, our ``client ID`` will not be used, even if one is required. .. code-block:: python mqtt_server = 'broker.hivemq.com' client_id = 'Jimmy' Connect to the MQTT agent and hold for one hour. If it fails, reset the Pico W. .. code-block:: python try: client = MQTTClient(client_id, mqtt_server, keepalive=3600) client.connect() print('Connected to %s MQTT Broker'%(mqtt_server)) except OSError as e: print('Failed to connect to the MQTT Broker. Reconnecting...') time.sleep(5) machine.reset() Create a variable ``topic``, which is the topic that the subscriber needs to follow. It should be the same as the topic filled in **step 4** of **2. Visit HiveMQ** above. Incidentally, ``b`` here converts string to byte, because MQTT is a binary based protocol were the control elements are binary bytes and not text strings. .. code-block:: python topic = b'SunFounder MQTT Test' Set interrupts for each button. When a button is pressed, a message is posted under ``topic``. .. code-block:: python def press1(pin): message = b'button 1 is pressed' client.publish(topic, message) print(message) sensor1.irq(trigger=machine.Pin.IRQ_RISING, handler=press1) * `UMQTT Client API `_ .. https://www.tomshardware.com/how-to/send-and-receive-data-raspberry-pi-pico-w-mqtt