README.md

# AIROC™ CYW43907 MQTT client

This code example demonstrates implementation of an MQTT client using the [MQTT client library](https://github.com/Infineon/mqtt). The library uses the AWS IoT device SDK MQTT client library that includes an MQTT 3.1.1 client.

In this example, the MQTT client RTOS task establishes a connection with the configured MQTT broker, and creates two tasks: publisher and subscriber. The publisher task publishes messages on a topic when the user button is pressed on the kit. The subscriber task subscribes to the same topic and controls the user LED based on the messages received from the MQTT broker. In case of unexpected disconnection of MQTT or Wi-Fi connection, the application executes a reconnection mechanism to restore the connection.


**Sequence of operation**

1. Press the user button.

2. The GPIO interrupt service routine (ISR) notifies the publisher task.

3. The publisher task publishes a message on a topic.

4. The MQTT broker sends back the message to the MQTT client because it is also subscribed to the same topic.

5. When the message is received, the subscriber task turns the LED ON or OFF. As a result, the user LED toggles every time the user presses the button.

[View this README on GitHub.](https://github.com/Infineon/mtb-example-cyw43907-mqtt-client)

[Provide feedback on this code example.](https://cypress.co1.qualtrics.com/jfe/form/SV_1NTns53sK2yiljn?Q_EED=eyJVbmlxdWUgRG9jIElkIjoiQ0UyMzQxMDAiLCJTcGVjIE51bWJlciI6IjAwMi0zNDEwMCIsIkRvYyBUaXRsZSI6IkFJUk9DJnRyYWRlOyBDWVc0MzkwNyBNUVRUIGNsaWVudCIsInJpZCI6InZlbG11cnVnYW4iLCJEb2MgdmVyc2lvbiI6IjIuMC4wIiwiRG9jIExhbmd1YWdlIjoiRW5nbGlzaCIsIkRvYyBEaXZpc2lvbiI6Ik1DRCIsIkRvYyBCVSI6IklDVyIsIkRvYyBGYW1pbHkiOiJXSUZJIn0=)


## Requirements

- [ModusToolbox™ software](https://www.infineon.com/modustoolbox) v3.1 or later (tested with v3.1)
- Board support package (BSP) minimum required version: 1.0.0
- Programming language: C
- Associated parts: [AIROC™ CYW43907 embedded wireless SoC ](https://www.infineon.com/cms/en/product/wireless-connectivity/airoc-connected-mcu/cyw43907)



## Supported toolchains (make variable 'TOOLCHAIN')

- GNU Arm® embedded compiler v11.3.1 (`GCC_ARM`) - Default value of `TOOLCHAIN`

## Supported kits (make variable 'TARGET')

- [AIROC™ CYW43907 embedded wireless SoC kit](https://www.infineon.com/cms/en/product/evaluation-boards/cyw943907aeval1f) (`CYW943907AEVAL1F`) – Default value of `TARGET`

## Hardware setup


This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly.



## Software setup

Install a terminal emulator if you don't have one. Instructions in this document use [PuTTY](https://www.putty.org/).

This code example implements a generic MQTT client that can connect to various MQTT brokers. In this document, the instructions to set up and run the MQTT client have been provided for the AWS IoT and Mosquitto MQTT brokers for reference. If you are using this code example with Mosquitto broker running locally on your PC, you need to download and install Mosquitto broker from https://mosquitto.org/download.

This example requires no additional software or tools if you are using the MQTT client with a publicly hosted MQTT broker.

## Using the code example

Create the project and open it using one of the following:

<details><summary><b>In Eclipse IDE for ModusToolbox&trade; software</b></summary>

1. Click the **New Application** link in the **Quick Panel** (or, use **File** > **New** > **ModusToolbox&trade; Application**). This launches the [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) tool.

2. Pick a kit supported by the code example from the list shown in the **Project Creator - Choose Board Support Package (BSP)** dialog.

   When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the [Library Manager](https://www.infineon.com/ModusToolboxLibraryManager) to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the **Quick Panel**.

   You can also just start the application creation process again and select a different kit.

   If you want to use the application for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.

3. In the **Project Creator - Select Application** dialog, choose the example by enabling the checkbox.

4. (Optional) Change the suggested **New Application Name**.

5. The **Application(s) Root Path** defaults to the Eclipse workspace, which is usually the desired location for the application. If you want to store the application in a different location, you can change the *Application(s) Root Path* value. Applications that share libraries should be in the same root path.

6. Click **Create** to complete the application creation process.

For more details, see the [Eclipse IDE for ModusToolbox&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mt_ide_user_guide.pdf*).

</details>

<details><summary><b>In command-line interface (CLI)</b></summary>

ModusToolbox&trade; software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The CLI tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the *{ModusToolbox&trade; software install directory}/tools_{version}/project-creator/* directory.

Use a CLI terminal to invoke the "project-creator-cli" tool. On Windows, use the command line "modus-shell" program provided in the ModusToolbox&trade; software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox&trade; software tools. You can access it by typing `modus-shell` in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.

The "project-creator-cli" tool has the following arguments:

Argument | Description | Required/optional
---------|-------------|-----------
`--board-id` | Defined in the `<id>` field of the [BSP](https://github.com/Infineon?q=bsp-manifest&type=&language=&sort=) manifest | Required
`--app-id`   | Defined in the `<id>` field of the [CE](https://github.com/Infineon?q=ce-manifest&type=&language=&sort=) manifest | Required
`--target-dir`| Specify the directory in which the application is to be created if you prefer not to use the default current working directory | Optional
`--user-app-name`| Specify the name of the application if you prefer to have a name other than the example's default name | Optional

<br />

The following example clones the "[mtb-example-cyw43907-mqtt-client](https://github.com/Infineon/mtb-example-cyw43907-mqtt-client)" application with the desired name "MqttClient" configured for the *CYW943907AEVAL1F* BSP into the specified working directory, *C:/mtb_projects*:

   ```
   project-creator-cli --board-id CYW943907AEVAL1F --app-id mtb-example-cyw43907-mqtt-client --user-app-name MqttClient --target-dir "C:/mtb_projects"
   ```

**Note:** The project-creator-cli tool uses the `git clone` and `make getlibs` commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the [ModusToolbox&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

To work with a different supported kit later, use the [Library Manager](https://www.infineon.com/ModusToolboxLibraryManager) to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal using `make library-manager` command or use the Library Manager CLI tool "library-manager-cli" to change the BSP.

The "library-manager-cli" tool has the following arguments:

Argument | Description | Required/optional
---------|-------------|-----------
`--add-bsp-name` | Name of the BSP that should be added to the application | Required
`--set-active-bsp` | Name of the BSP that should be as active BSP for the application | Required
`--add-bsp-version`| Specify the version of the BSP that should be added to the application if you do not wish to use the latest from manifest | Optional
`--add-bsp-location`| Specify the location of the BSP (local/shared) if you prefer to add the BSP in a shared path | Optional

<br />

Following example adds the CYW943907AEVAL1F BSP to the already created application and makes it the active BSP for the app:

   ```
   ~/ModusToolbox/tools_{3.1}/library-manager/library-manager-cli --project "C:/mtb-example-cyw43907-mqtt-client" --add-bsp-name CYW943907AEVAL1F --add-bsp-version "latest-v1.X" --add-bsp-location "local"

   ~/ModusToolbox/tools_{3.1}/library-manager/library-manager-cli --project "C:mtb-example-cyw43907-mqtt-client" --set-active-bsp APP_CYW943907AEVAL1F
   ```

</details>

<details><summary><b>In third-party IDEs</b></summary>

Use one of the following options:

- **Use the standalone [Project Creator](https://www.infineon.com/ModusToolboxProjectCreator) tool:**

   1. Launch Project Creator from the Windows Start menu or from *{ModusToolbox&trade; software install directory}/tools_{version}/project-creator/project-creator.exe*.

   2. In the initial **Choose Board Support Package** screen, select the BSP, and click **Next**.

   3. In the **Select Application** screen, select the appropriate IDE from the **Target IDE** drop-down menu.

   4. Click **Create** and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

<br />

- **Use command-line interface (CLI):**

   1. Follow the instructions from the **In command-line interface (CLI)** section to create the application, and then import the libraries using the `make getlibs` command.

   2. Export the application to a supported IDE using the `make <ide>` command.

   3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the [ModusToolbox&trade; software user guide](https://www.infineon.com/ModusToolboxUserGuide) (locally available at *{ModusToolbox&trade; software install directory}/docs_{version}/mtb_user_guide.pdf*).

</details>


## Operation

1. Connect the board to your PC using the provided USB cable through the micro-USB USB connector.

2. Modify the user configuration files in the *configs* directory as follows:

      1. **Wi-Fi configuration:** Set the Wi-Fi credentials in *configs/wifi_config.h*: Modify the macros `WIFI_SSID`, `WIFI_PASSWORD`, and `WIFI_SECURITY` to match with that of the Wi-Fi network that you want to connect.

      2. **MQTT configuration:** Set up the MQTT client and configure the credentials in *configs/mqtt_client_config.h*. Some of the important configuration macros are as follows:

         - `MQTT_BROKER_ADDRESS`: Hostname of the MQTT broker

         - `MQTT_PORT`: Port number to be used for the MQTT connection. As specified by IANA (Internet Assigned Numbers Authority), port numbers assigned for MQTT protocol are *1883* for non-secure connections and *8883* for secure connections. However, MQTT brokers may use other ports. Configure this macro as specified by the MQTT broker.

         - `MQTT_SECURE_CONNECTION`: Set this macro to `1` if a secure (TLS) connection to the MQTT broker is  required to be established; else `0`.

         - `MQTT_USERNAME` and `MQTT_PASSWORD`: User name and password for client authentication and authorization, if required by the MQTT broker. However, note that this information is generally not encrypted and the password is sent in plain text. Therefore, this is not a recommended method of client authentication.

         - `CLIENT_CERTIFICATE` and `CLIENT_PRIVATE_KEY`: Certificate and private key of the MQTT client used for client authentication. Note that these macros are applicable only when `MQTT_SECURE_CONNECTION` is set to `1`.

         - `ROOT_CA_CERTIFICATE`: Root CA certificate of the MQTT broker

         See [Setting up the MQTT broker](#setting-up-the-mqtt-broker) to learn how to configure these macros for AWS IoT and Mosquitto MQTT brokers.

         For a full list of configuration macros used in this code example, see [Wi-Fi and MQTT configuration macros](#wi-fi-and-mqtt-configuration-macros).

      3. Other configuration files: You can optionally modify the configuration macros in the following files according to your application:

         - *configs/core_mqtt_config.h* used by the [MQTT library](https://github.com/Infineon/mqtt)

         - *configs/FreeRTOSConfig.h* used by the [FreeRTOS library](https://github.com/Infineon/freertos)

3. Open a terminal program and select the respective COM port. Set the serial port parameters to 8N1 and 115200 baud.

4. Program the board using one of the following:

   <details><summary><b>Using Eclipse IDE for ModusToolbox&trade; software</b></summary>

      1. Select the application project in the Project Explorer.

      2. In the **Quick Panel**, scroll down, and click **\<Application Name> Program (FTDI)**.
   </details>

   <details><summary><b>Using CLI</b></summary>

     From the terminal, execute the `make program` command to build and program the application using the default toolchain to the default target. The default toolchain and target are specified in the application's Makefile but you can override these values manually:
      ```
      make program TARGET=<BSP> TOOLCHAIN=<toolchain>
      ```

      Example:
      ```
      make program TARGET=CYW943907AEVAL1F TOOLCHAIN=GCC_ARM
      ```
   </details>

5. After programming, the application starts automatically. Observe the messages on the UART terminal, and wait for the device to make all the required connections.

   **Figure 1. Application initialization status**

   ![](images/application_initialization.png)

6. Once the initialization is complete, confirm that the message *"Press the user button (SW2) to publish "TURN ON"/"TURN OFF" on the topic 'ledstatus'..."* is printed on the UART terminal. This message may vary depending on the MQTT topic and publish messages that are configured in the *mqtt_client_config.h* file.

7.. Press the user button (SW2) on the kit to toggle the LED state.

8. Confirm that the user LED state is toggled and the messages received on the subscribed topic are printed on the UART terminal.

   **Figure 2. Publisher and subscriber logs**

   ![](images/publish_subscribe_messages.png)

This example can be programmed on multiple kits (*only when `GENERATE_UNIQUE_CLIENT_ID` is set to `1`*); the user LEDs on all the kits will synchronously toggle with button presses on any kit.

Alternatively, the publish and subscribe functionalities of the MQTT client can be individually verified if the MQTT broker supports a test MQTT client like the AWS IoT.

- *To verify the subscribe functionality*: Using the test MQTT client, publish messages such as "TURN ON" and "TURN OFF" on the topic specified by the `MQTT_PUB_TOPIC` macro in *mqtt_client_config.h* to control the LED state on the kit.

- *To verify the publish functionality*: From the Test MQTT client, subscribe to the MQTT topic specified by the `MQTT_SUB_TOPIC` macro and confirm that the messages published by the kit (when the user button is pressed) are displayed on the test MQTT client's console.


## Debugging

You can debug the example to step through the code. In the IDE, use the **\<Application Name> Debug (FTDI)** configuration in the **Quick Panel**. For more details, see the "Program and debug" section in the [Eclipse IDE for ModusToolbox&trade; software user guide](https://www.infineon.com/MTBEclipseIDEUserGuide).

## Design and implementation

This example implements three RTOS tasks: MQTT client, publisher, and subscriber. The main function initializes the BSP and the retarget-io library, and creates the MQTT client task.

The MQTT client task initializes the Wi-Fi connection manager (WCM) and connects to a Wi-Fi access point (AP) using the Wi-Fi network credentials that are configured in *wifi_config.h*. Upon a successful Wi-Fi connection, the task initializes the MQTT library and establishes a connection with the MQTT broker/server.

The MQTT connection is configured to be secured by default; the secure connection requires a client certificate, a private key, and the Root CA certificate of the MQTT broker that are configured in *mqtt_client_config.h*.

After a successful MQTT connection, the subscriber and publisher tasks are created. The MQTT client task then waits for commands from the other two tasks and callbacks to handle events like unexpected disconnections.

The subscriber task initializes the user LED GPIO and subscribes to messages on the topic specified by the `MQTT_SUB_TOPIC` macro that can be configured in *mqtt_client_config.h*. When the subscriber task receives a message from the broker, it turns the user LED ON or OFF depending on whether the received message is "TURN ON" or "TURN OFF" (configured using the `MQTT_DEVICE_ON_MESSAGE` and `MQTT_DEVICE_OFF_MESSAGE` macros).

The publisher task sets up the user button GPIO and configures an interrupt for the button. The ISR notifies the publisher task upon a button press. The publisher task then publishes messages (*TURN ON* / *TURN OFF*) on the topic specified by the `MQTT_PUB_TOPIC` macro. When the publish operation fails, a message is sent over a queue to the MQTT client task.

An MQTT event callback function `mqtt_event_callback()` invoked by the MQTT library for events like MQTT disconnection and incoming MQTT subscription messages from the MQTT broker. In the case of an MQTT disconnection, the MQTT client task is informed about the disconnection using a message queue. When an MQTT subscription message is received, the subscriber callback function implemented in *subscriber_task.c* is invoked to handle the incoming MQTT message.

The MQTT client task handles unexpected disconnections in the MQTT or Wi-Fi connections by initiating reconnection to restore the Wi-Fi and/or MQTT connections. Upon failure, the publisher and subscriber tasks are deleted, cleanup operations of various libraries are performed, and then the MQTT client task is terminated.

### Configuring the MQTT client

#### Wi-Fi and MQTT configuration macros

 Macro                               |  Description
 :---------------------------------- | :------------------------
 **Wi-Fi Connection Configurations**  |  In *configs/wifi_config.h*
 `WIFI_SSID`       | SSID of the Wi-Fi AP to which the MQTT client connects
 `WIFI_PASSWORD`   | Passkey/password for the Wi-Fi SSID specified above
 `WIFI_SECURITY`   | Security type of the Wi-Fi AP. See `cy_wcm_security_t` structure in *cy_wcm.h* file for details.
 `MAX_WIFI_CONN_RETRIES`   | Maximum number of retries for Wi-Fi connection
 `WIFI_CONN_RETRY_INTERVAL_MS`   | Time interval in milliseconds in between successive Wi-Fi connection retries
 **MQTT Connection Configurations**  |  In *configs/mqtt_client_config.h*
 `MQTT_BROKER_ADDRESS`      | Hostname of the MQTT broker
 `MQTT_PORT`                | Port number to be used for the MQTT connection. As specified by IANA, port numbers assigned for MQTT protocol are *1883* for non-secure connections and *8883* for secure connections. However, MQTT brokers uses other ports. Configure this macro as specified by the MQTT broker.
 `MQTT_SECURE_CONNECTION`   | Set this macro to `1` if a secure (TLS) connection to the MQTT broker is  required to be established; else `0`.
 `MQTT_USERNAME` <br> `MQTT_PASSWORD`   | Username and password for client authentication and authorization, if required by the MQTT broker. However, note that this information is generally not encrypted and the password is sent in plain text. Therefore, this is not a recommended method of client authentication.
 **MQTT Client Certificate Configurations**  |  In *configs/mqtt_client_config.h*
 `CLIENT_CERTIFICATE` <br> `CLIENT_PRIVATE_KEY`  | Certificate and private key of the MQTT client used for client authentication. Note that these macros are applicable only when `MQTT_SECURE_CONNECTION` is set to `1`.
 `ROOT_CA_CERTIFICATE`      |  Root CA certificate of the MQTT broker
 **MQTT Message Configurations**    |  In *configs/mqtt_client_config.h*
 `MQTT_PUB_TOPIC`           | MQTT topic to which the messages are published by the Publisher task to the MQTT broker
 `MQTT_SUB_TOPIC`           | MQTT topic to which the subscriber task subscribes to. The MQTT broker sends the messages to the subscriber that are published in this topic (or equivalent topic).
 `MQTT_MESSAGES_QOS`        | The Quality of Service (QoS) level to be used by the publisher and subscriber. Valid choices are `0`, `1`, and `2`.
 `ENABLE_LWT_MESSAGE`       | Set this macro to `1` if you want to use the 'Last Will and Testament (LWT)' option; else `0`. LWT is an MQTT message that will be published by the MQTT broker on the specified topic if the MQTT connection is unexpectedly closed. This configuration is sent to the MQTT broker during MQTT connect operation; the MQTT broker will publish the Will message on the Will topic when it recognizes an unexpected disconnection from the client.
 `MQTT_WILL_TOPIC_NAME` <br> `MQTT_WILL_MESSAGE`   | The MQTT topic and message for the LWT option described above. These configurations are applicable only when `ENABLE_LWT_MESSAGE` is set to `1`.
 `MQTT_DEVICE_ON_MESSAGE` <br> `MQTT_DEVICE_OFF_MESSAGE`  | The MQTT messages that control the device (LED) state in this code example.
 **Other MQTT Client Configurations**    |  In *configs/mqtt_client_config.h*
 `GENERATE_UNIQUE_CLIENT_ID`   | Every active MQTT connection must have a unique client identifier. If this macro is set to `1`, the device will generate a unique client identifier by appending a timestamp to the string specified by the `MQTT_CLIENT_IDENTIFIER` macro. This feature is useful if you are using the same code on multiple kits simultaneously.
 `MQTT_CLIENT_IDENTIFIER`     | The client identifier (client ID) string to be used during MQTT connection. If `GENERATE_UNIQUE_CLIENT_ID` is set to `1`, a timestamp is appended to this macro value and used as the client ID; else, the value specified for this macro is directly used as the client ID.
 `MQTT_CLIENT_IDENTIFIER_MAX_LEN`   | The longest client identifier that an MQTT server must accept (as defined by the MQTT 3.1.1 spec) is 23 characters. However, some MQTT brokers support longer client IDs. Configure this macro as per the MQTT broker specification.
 `MQTT_TIMEOUT_MS`            | Timeout in milliseconds for MQTT operations in this example
 `MQTT_KEEP_ALIVE_SECONDS`    | The keepalive interval in seconds used for MQTT ping request
 `MQTT_ALPN_PROTOCOL_NAME`   | The application layer protocol negotiation (ALPN) protocol name to be used that is supported by the MQTT broker in use. Note that this is an optional macro for most of the use cases. <br>Per IANA, the port numbers assigned for MQTT protocol are 1883 for non-secure connections and 8883 for secure connections. In some cases, there is a need to use other ports for MQTT like port 443 (which is reserved for HTTPS). ALPN is an extension to TLS that allows many protocols to be used over a secure connection.
 `MQTT_SNI_HOSTNAME`   | The server name indication (SNI) host name to be used during the transport layer security (TLS) connection as specified by the MQTT broker. <br>SNI is extension to the TLS protocol. As required by some MQTT brokers, SNI typically includes the hostname in the "Client Hello" message sent during TLS handshake.
 `MQTT_NETWORK_BUFFER_SIZE`   | A network buffer is allocated for sending and receiving MQTT packets over the network. Specify the size of this buffer using this macro. Note that the minimum buffer size is defined by the `CY_MQTT_MIN_NETWORK_BUFFER_SIZE` macro in the MQTT library.
 `MAX_MQTT_CONN_RETRIES`   | Maximum number of retries for MQTT connection
 `MQTT_CONN_RETRY_INTERVAL_MS`   | Time interval in milliseconds in between successive MQTT connection retries

<br>

#### Setting up the MQTT broker

<details><summary><b>AWS IoT MQTT</b></summary>

 1. Set up the MQTT device (also known as a *Thing*) in the AWS IoT core as described in the [Getting started with AWS IoT tutorial](https://docs.aws.amazon.com/iot/latest/developerguide/iot-gs.html).

    **Note:** While setting up your device, ensure that the policy associated with this device permits all MQTT operations (*iot:Connect*, *iot:Publish*, *iot:Receive*, and *iot:Subscribe*) for the resource used by this device. For testing purposes, it is recommended to have the following policy document which allows all *MQTT Policy Actions* on all *Amazon Resource Names (ARNs)*.
    ```
    {
        "Version": "2012-10-17",
        "Statement": [
            {
                "Effect": "Allow",
                "Action": "iot:*",
                "Resource": "*"
            }
        ]
    }
    ```

 2. In the *configs/mqtt_client_config.h* file, set `MQTT_BROKER_ADDRESS` to your custom endpoint on the **Settings** page of the AWS IoT console. This has the format `ABCDEFG1234567.iot.<region>.amazonaws.com`.

 3. Set the macros `MQTT_PORT` to `8883` and `MQTT_SECURE_CONNECTION` to `1` in the *configs/mqtt_client_config.h* file.

 4. Download the following certificates and keys that are created and activated in the **Step 3**:

       - A certificate for the AWS IoT Thing - *xxxxxxxxxx.cert.pem*
       - A public key - *xxxxxxxxxx.public.key*
       - A private key - *xxxxxxxxxx.private.key*
       - Root CA "RSA 2048 bit key: Amazon Root CA 1" for AWS IoT from [CA certificates for server authentication](https://docs.aws.amazon.com/iot/latest/developerguide/server-authentication.html#server-authentication-certs).

 5. Using these certificates and keys, enter the following parameters in *mqtt_client_config.h* in Privacy-Enhanced Mail (PEM) format:
       - `CLIENT_CERTIFICATE` - *xxxxxxxxxx.cert.pem*
       - `CLIENT_PRIVATE_KEY` - *xxxxxxxxxx.private.key*
       - `ROOT_CA_CERTIFICATE` - Root CA certificate

    You can either convert the values to strings manually following the format shown in *mqtt_client_config.h* or you can use the HTML utility available [here](https://github.com/Infineon/amazon-freertos/blob/master/tools/certificate_configuration/PEMfileToCString.html) to convert the certificates and keys from PEM format to C string format. You need to clone the repository from GitHub to use the utility.

</details>

Although this section provides instructions only for AWS IoT, the MQTT client implemented in this example is generic. It is expected to work with other MQTT brokers with appropriate configurations. See the [list of publicly-accessible MQTT brokers](https://github.com/mqtt/mqtt.github.io/wiki/public_brokers) that can be used for testing and prototyping purposes.

**Note:** Please refer the following link for MQTT ports supported in AWS https://docs.aws.amazon.com/iot/latest/developerguide/protocols.html

### Resources and settings

**Table 1. Application resources**

 Resource  |  Alias/object     |    Purpose
 :------- | :------------    | :------------
 UART (HAL)|cy_retarget_io_uart_obj| UART HAL object used by retarget-io for Debug UART port
 GPIO (HAL)    | CYBSP_USER_LED2         | User LED controlled by the subscriber based on incoming MQTT messages
 GPIO (HAL)    | CYBSP_SW1         | User button used to notify the publisher to publish MQTT messages

<br />

## Related resources

Resources  | Links
-----------|----------------------------------
Code examples  | [Using ModusToolbox&trade; software](https://github.com/Infineon/Code-Examples-for-ModusToolbox-Software) on GitHub <br>
Device documentation | [AIROC&trade; CYW43907 datasheet](https://www.infineon.com/dgdl/Infineon-CYW43907-WICED-IEEE-802.11-a-b-g-n-SoC-with-an-Embedded-Applications-Processor-AdditionalTechnicalInformation-v13_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ee1fbda682d) <br>
Development kits | Select your kits from the [evaluation board finder](https://www.infineon.com/cms/en/design-support/finder-selection-tools/product-finder/evaluation-board)
Libraries on GitHub  | [mtb-hal-cat4](https://github.com/Infineon/mtb-hal-cat4) – AIROC&trade; CYW43907 Hardware abstraction layer (HAL) library <br> [retarget-io](https://github.com/Infineon/retarget-io) – Utility library to retarget STDIO messages to a UART port <br>
Middlewares on GitHub  | [ModusToolbox™ software](https://github.com/Infineon/modustoolbox-software) – Links to all ModusToolbox™ middlewares, libraries and documents<br>
Tools  | [Eclipse IDE for ModusToolbox&trade; software](https://www.infineon.com/modustoolbox) – ModusToolbox&trade; software is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC&trade; Wi-Fi and Bluetooth&reg; connectivity devices

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## Other resources

Infineon provides a wealth of data at [www.infineon.com](https://www.infineon.com) to help you select the right device, and quickly and effectively integrate it into your design.

## Document history

Document title: *CE234100* - *AIROC&trade; CYW43907 MQTT client*

 Version | Description of change
 ------- | ---------------------
 1.0.0   | New code example
 2.0.0   | Major update to support ModusToolbox™ v3.1 and BSPs v1.0.0 <br /> This version is not backward compatible with previous versions (below ModusToolbox™ v3.0) of ModusToolbox&trade; software 

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