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MQTT Client Example

Description

This example demonstrates the use of the Wi-Fi module with the Pitaya Go board to implement an MQTT client using the MQTT protocol.

For more about MQTT, see the MQTT Version 3.1.1 Specification.

This example also implements the Command Line Interface over BLE NUS and USB CDC ACM. Both consoles can be opened and used independently.

Tip

Before you start building, remember to set up the nRF5 SDK development environment first. See Setup the nRF5 SDK for details.

Building the example

You can find the source code and the project file of the example in the following folder: pitaya-go/examples/wifi/mqtt_client_example.

Open terminal and navigate to the directory with the example Makefile:

cd ./pitaya-go/examples/wifi/mqtt_client_example/armgcc

Run make to build the example:

make

Programming the firmware

If compiled successfully, the firmware is located in mqtt_client_example/armgcc/_build with the name nrf52840_xxaa.hex.

While pushing the USER button, press the RESET button to enter the DFU mode. Then program the firmware using the nRF Connect for Desktop tool.

If the SoftDevice is not programmed before, remember to add the SoftDevice. The SoftDevice is located in <nRF5 SDK>/components/softdevice/s140/hex/s140_nrf52_6.1.0_softdevice.hex.

Tip

See Programming section for details about how to program your Pitaya Go.

Testing

The application is now programmed and running. Perform the following steps to test the MQTT client:

  1. Run a terminal application like PuTTY or screen:

    screen /dev/cu.usbmodemD2E39D222D781 115200

  2. Press Enter in the terminal. A console prompt is displayed.

  3. Use the Tab key to print the available commands.

  4. Use command wifi connect {SSID} {PSK} to connect to your AP. The parameters stand for the following:

    • {SSID}: The name of AP. If not specified, the device will attempt to reconnect to the last-associated AP.
    • {PSK}: The passphrase of AP. MUST be 8 characters or more. If it's an Open network, it can be left blank.

  5. Observe that BLUE LED is lit, that is, the Wi-Fi is connected.

  6. Use command mqtt connect iot.eclipse.org to connect the MQTT broker.

  7. Use command mqtt sub pitayago to subscribe the topic pitayago.

  8. Use command mqtt pub pitayago "Hello World!" to publish Hello World! to the topic pitayago. Observe that the message should be received.

  9. Head to https://www.eclipse.org/paho/clients/js/utility/, connect the same broker and publish a message to the same topic above. Observe that Pitaya Go will receive the message.

  10. You can also use the Web Device CLI application to test this example.

Reference

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