This code example demonstrates an OTA update with PSoC™ 6 MCU and CYW43xxx connectivity devices. The device establishes a connection with the designated MQTT broker (this example uses a local Mosquitto broker). It periodically checks the job document to see if a new update is available. When a new update is available, it is downloaded and written to the secondary slot. On the next reboot, MCUboot swaps the new image in the secondary slot with the primary slot image and runs the application. If the new image is not validated in runtime, on the next reboot MCUboot reverts to the previously validated image.

MCUboot is a secure bootloader for 32-bit MCUs. See the README of the mtb-example-psoc6-mcuboot-basic code example for more details.

The OTA feature is enabled by the Over-the-air update middleware library. See the ota middleware repository on Github for more details.

View this README on GitHub.

Provide feedback on this code example.

• ModusToolbox™ software v2.4 or later.
• Board support package (BSP) minimum required version: 3.0.0
• Programming language: C
• Associated parts: All PSoC™ 6 MCU parts with SDIO interface

• GNU Arm® embedded compiler v10.3.1 (GCC_ARM) - Default value of TOOLCHAIN
• Arm® compiler v6.13 (ARM)
• IAR C/C++ compiler v8.42.2 (IAR)

This example requires PSoC™ 6 MCU devices with at least 2-MB flash and 1-MB SRAM, and therefore supports only the following kits:

• PSoC™ 6 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062-4343W) - Default value of TARGET
• PSoC™ 62S2 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062S2-43012)
• PSoC™ 62S2 evaluation kit (CY8CEVAL-062S2-LAI-4373M2, CY8CEVAL-062S2-MUR-43439M2)

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

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.

This examples uses Mosquitto to setup a local MQTT broker, see section Setting up the local MQTT Mosquitto broker for more details.

This code example is a dual-core project, where the MCUboot bootloader app runs on the CM0+ core and the OTA update app runs on the CM4 core. The OTA update app fetches the new image and places it in the flash memory; the bootloader takes care of updating the existing image with the new image. The mtb-example-psoc6-mcuboot-basic code example is the bootloader project used for this purpose.

The bootloader project and this OTA update project should be built and programmed independently. They must be placed separately in the workspace as you would do for any other two independent projects. An example workspace would look something like this:

<example-workspace>
   |
   |-<mtb-example-psoc6-mcuboot-basic>
   |-<mtb-example-ota-mqtt>
   |

You must first build and program the MCUboot bootloader project into the CM0+ core; this needs to be done only once. The OTA update app can then be programmed into the CM4 core; you need to only modify this app for all application purposes.

The mtb-example-psoc6-mcuboot-basic code example bundles two applications: the bootloader app that runs on CM0+, and the Blinky app that runs on CM4. For this code example, only the bootloader app is required and the root directory of the bootloader app is referred to as <bootloader_cm0p> in this document.

1. Import the mtb-example-psoc6-mcuboot-basic code example per the instructions in the Using the code example section of its README.

2. The bootloader and OTA applications must have the same understanding of the memory layout. Override the default memory layout by editing the make variables in the <bootloader_cm0p>/shared_config.mk file. For this example, perform the following edits to match the memory layout with the OTA application:

   ifeq ($(USE_EXT_FLASH), 1)
   MCUBOOT_SLOT_SIZE=0x1C0000
   else
   MCUBOOT_SLOT_SIZE=0xF0000
   endif
   .
   .
   .
   MCUBOOT_SCRATCH_SIZE=0x4000
   

3. Copy the <mtb_shared>/mcuboot/<tag>/boot/cypress/MCUBootApp/config folder and paste it in the <bootloader_cm0p> folder.

4. Edit the <bootloader_cm0p>/config/mcuboot_config/mcuboot_config.h file and comment out the following defines to skip checking the image signature:

   #define MCUBOOT_SIGN_EC256
   #define NUM_ECC_BYTES (256 / 8)
   .
   .
   .
   #define MCUBOOT_VALIDATE_PRIMARY_SLOT
   

5. Edit <bootloader_cm0p>/app.mk and replace the MCUboot include $(MCUBOOTAPP_PATH)/config with ./config. This gets the build system to find the new copy of the config directory that you pasted in the <bootloader_cm0p> directory, instead of the default one supplied by the library.

6. Edit <bootloader_cm0p>/Makefile:

   1. Set USE_EXT_FLASH to '1', to use the external flash to store the secondary image.

   2. Set SWAP_UPGRADE to '1', to enable swap feature of MCUboot.

7. Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.

8. Open a CLI terminal.

   On Linux and macOS, you can use any terminal application. On Windows, open the modus-shell app from the Start menu.

9. Navigate the terminal to the <mtb_shared>/mcuboot/<tag>/scripts folder.

10. Run the following command to ensure that the required modules are installed or already present ("Requirement already satisfied:" is printed).

    pip install -r requirements.txt
    

11. Open a serial terminal emulator and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.

12. Build and program the application per the Step-by-step instructions in its README.

    After programming, the bootloader application starts automatically.

    Figure 1. Booting with no bootable image

    

Note: This example does not demonstrate securely upgrading the image and booting from it using features such as image-signing and secured boot. See the PSoC™ 64 line of "Secure" MCUs that offer all those features built around MCUboot.

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

project-creator-cli --board-id CY8CKIT-062-WIFI-BT --app-id mtb-example-psoc6-hello-world --user-app-name MyHelloWorld --target-dir "C:/mtb_projects"

The root directory of the OTA application is referred to as <OTA Application> in this document.

This code example uses the locally installable Mosquitto that runs on your computer as the default broker. You can also use one of the other public MQTT brokers listed at https://github.com/mqtt/mqtt.github.io/wiki/public_brokers.

1. Download the executable setup from Mosquitto downloads site.

2. Run the setup to install the software. During installation uncheck the Service component. Also, note down the installation directory.

3. Once the installation is complete, add the installation directory to the system PATH.

4. Open a CLI terminal.

   On Linux and macOS, you can use any terminal application. On Windows, open the modus-shell app from the Start menu

5. Navigate to the <OTA Application>/scripts/ folder.

6. Execute the following command to generate self-signed SSL certificates and keys. On Linux and macOS, you can get your device local IP address by running the ifconfig command on any terminal application. On Windows, run the ipconfig command on a command prompt.

   sh generate_ssl_cert.sh <local-ip-address-of-your-pc>
   

   Example:

   sh generate_ssl_cert.sh 192.168.0.10
   

   This step will generate the following files in the same <OTA Application>/scripts/ directory:

   1. mosquitto_ca.crt - Root CA certificate
   2. mosquitto_ca.key - Root CA private key
   3. mosquitto_server.crt - Server certificate
   4. mosquitto_server.key - Server private key
   5. mosquitto_client.crt - Client certificate
   6. mosquitto_client.key - Client private key

7. The <OTA Application>/scripts/mosquitto.conf file is pre-configured for starting the Mosquitto server for this code example. You can edit the file if you wish to make other changes to the broker settings.

8. Starting the Mosquitto MQTT server:

   • Using the code example in TLS mode (default):

     1. Execute the following command:

        mosquitto -v -c mosquitto.conf
        

   • Using the code example in Non-TLS mode:

     1. Edit the <OTA Application>/scripts/mosquitto.conf file and change the value of require_certificate parameter to false.

     2. Execute the following command:

        mosquitto -v -c mosquitto.conf
        

1. Open a CLI terminal.

   On Linux and macOS, you can use any terminal application. On Windows, open the modus-shell app from the Start menu.

2. Navigate to the <OTA Application>/scripts/ folder.

3. Run the following command to ensure that the required Python modules are installed or already present ("Requirement already satisfied:" is printed).

   pip install -r requirements.txt
   

4. Edit the <OTA Application>/scripts/publisher.py file and change the value of the variable MOSQUITTO_BROKER_LOCAL_ADDRESS to the local IP address of your PC.

5. Run the publisher.py python script.

   The scripts takes arguments such as kit name, broker URL, and file path. For details on the supported arguments and their usage, execute the following command.

   python publisher.py --help
   

   To start the publisher script for the default settings of this example, execute the following command:

   python publisher.py tls
   

1. Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.

2. Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.

3. Edit the <OTA Application>/source/ota_app_config.h file to configure your OTA application:

   1. Modify the connection configuration such as WIFI_SSID, WIFI_PASSWORD, and WIFI_SECURITY to match the settings of your Wi-Fi network. Make sure the device running the MQTT broker and the kit are connected to the same network.

   2. Modify the value of MQTT_BROKER_URL to the local IP address of your MQTT broker.

   3. By default, this code example works in TLS mode. To use the example in non-TLS mode, modify ENABLE_TLS to false and skip the next step of adding the certificate.

   4. Add the certificates and key:

      1. Open a CLI terminal.

         On Linux and macOS, you can use any terminal application. On Windows, open the modus-shell app from the Start menu.

      2. Navigate the terminal to <OTA Application>/scripts/ directory.

      3. Run the format_cert_key.py Python script to generate the string format of the certificate and key files that can be added as a macro. Pass the name of the certificate or key with the extension as an argument to the Python script:

         python format_cert_key.py <one-or-more-file-name-of-certificate-or-key-with-extension>
         

         Example:

         python format_cert_key.py mosquitto_ca.crt mosquitto_client.crt mosquitto_client.key
         

      4. Copy the generated strings and add it to the ROOT_CA_CERTIFICATE, CLIENT_CERTIFICATE and CLIENT_KEY macros per the sample shown.

4. Edit the job document (<OTA Application>/scripts/ota_update.json):

   1. Modify the value of Broker to match the IP address of your MQTT broker.

   2. Modify the value of Board to match the kit you are using.

   3. In Step 3, if the code example has been configured to work in non-TLS mode: Set the value of Port to 1883.

5. Program the board using one of the following:

   Using Eclipse IDE for ModusToolbox™ software

   1. Select the application project in the Project Explorer.

   2. In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).

   Using CLI

   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 those values manually:

   make program TARGET=<BSP> TOOLCHAIN=<toolchain>
   

   Example:

   make program TARGET=CY8CPROTO-062-4343W TOOLCHAIN=GCC_ARM
   

   At this point, the primary slot is programmed. The CM4 CPU starts running the image from the primary slot on reset. Observe the messages on the UART terminal and wait for the device to make the required connections as shown in Figure 2. Observe that the user LED blinks at 1 Hz.

   Figure 2. Connection to the MQTT broker

   

6. The Job document placed in the <OTA Application>/scripts/ folder has a value of Version as 1.0.0. Because the OTA application version and the available update version are the same, the update will not happen.

7. Modify the value of the BLINKY_DELAY_MS macro to (100) in the <OTA Application>/source/led_task.c file and change the app version in the <OTA Application>/Makefile by setting APP_VERSION_MINOR to '1'.

8. Build the app (DO NOT program it to the kit). This new image will be published to the MQTT broker in the following steps to demonstrate the OTA update.

   Using Eclipse IDE for ModusToolbox™ software

   1. Select the application project in the Project Explorer.

   2. In the Quick Panel, scroll down, and click Build <OTA Application> Application.

  1. From the terminal, execute the `make build` command to build the application using the default toolchain to the default target. You can specify a target and toolchain manually:
     ```
     make build TARGET=<BSP> TOOLCHAIN=<toolchain>
     ```
     Example:
     ```
     make build TARGET=CY8CPROTO-062-4343W TOOLCHAIN=GCC_ARM
     ```

9. After a successful build, edit the <OTA Application>/scripts/ota_update.json file to modify the value of Version to 1.1.0.

10. The OTA application now finds the updated Job document, downloads the new image, and places it in the secondary slot. Once the download is complete, a soft reset is issued. The MCUboot bootloader starts the image upgrade process.

    Figure 3. Image download

    

11. After the image upgrade is successfully completed, observe that the user LED is now blinking at 10 Hz.

12. To test the revert feature of MCUboot, we can send a bad image as v1.2.0 OTA update. The bad image used in this example is an infinite loop. The watchdog timer will reset the bad image and upon reboot, MCUboot will revert the primary image back to v1.1.0 good image. Edit <OTA Application>/Makefile and add TEST_REVERT to the Defines variable as shown:

    DEFINES+=CY_RTOS_AWARE HTTP_DO_NOT_USE_CUSTOM_CONFIG TEST_REVERT
    

13. Edit the app version in the <OTA Application>/Makefile by setting APP_VERSION_MINOR to '2'.

14. Build the application per Step 8.

15. After a successful build, edit the <OTA Application>/scripts/ota_update.json file to modify the value of Version to 1.2.0.

16. The OTA application will now find this new v1.2.0 image and update to it. After the update, within a few seconds, the watchdog timer resets the devices. Upon reset, MCUboot reverts to the v1.1.0 good image.

You can debug the example to step through the code. In the IDE, use the <OTA Application> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ software user guide.

Note: (Only while debugging) On the CM4 CPU, some code in main() may execute before the debugger halts at the beginning of main(). This means that some code executes twice - once before the debugger stops execution, and again after the debugger resets the program counter to the beginning of main(). See KBA231071 to learn about this and for the workaround.

This example implements two RTOS tasks: OTA client and LED blink. Both these tasks are independent and do not communicate with each other. The OTA client task initializes the dependent middleware and starts the OTA agent. The LED task blinks the user LED at a specified delay.

All the source files related to the two tasks are placed under the <OTA Application>/source/ directory:

All the scripts and configurations needed for this example are placed under the <OTA Application>/scripts/ directory:

The <OTA Application>/configs/ folder contains other configurations related to the OTA middleware, FreeRTOS, and MBEDTLS.

Figure 4 shows the flow of the OTA update process using MQTT. The application which needs OTA updates should run the OTA agent. The OTA agent spawns threads to receive OTA updates when available, without intervening with the application's core functionality.

The initial application resides in the primary slot of the flash memory. When the OTA agent receives an update, the new image is placed in the secondary slot of the flash memory. On the next reboot, MCUboot copies the image from the secondary slot into the primary slot and then CM4 will boot the upgraded image from the primary slot.

Figure 4. Overview of OTA update using MQTT

For more details on the features and configurations offered by the ota library, see its README.

Both MCUboot and the application must have an identical understanding of the memory layout. Otherwise, the bootloader may consider an authentic image as invalid. For more details on the features and configurations of MCUboot-based bootloader, see the README of the mtb-example-psoc6-mcuboot-basic code example.

Table 1. Application resources

Cypress provides a wealth of data at www.cypress.com to help you select the right device, and quickly and effectively integrate it into your design.

For PSoC™ 6 MCU devices, see How to design with PSoC™ 6 MCU - KBA223067 in the Cypress community.

Document title: CE230031 - Over-the-air firmware update using MQTT

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