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Nx_MQTT_Client_wifi application description

This application provides an example of Azure RTOS NetX/NetXDuo stack usage.

It shows how to exchange data between client and server using MQTT protocol in an encrypted mode supporting TLS v1.2.

  • a dns_client is created to be used as DNS server then it gets MQTT broker address from MQTT_BROKER_NAME predefined on app_netxduo.h file.

  • a mqtt_client is created to connect to the online MQTT broker; connection with server will be secure and a tls_setup_callback will set the TLS parameters. By default, MQTT_PORT for encrypted mode is 8883. Refer to note below, to know how to setup an x509 certificate.

  • the mqtt_client subscribes on a predefined topic TOPIC_NAME "stm32_rng_value" with a Quality Of Service QOS0

  • depending on the number of messages NB_MESSAGE defined by the user, mqtt_client will publish a random number generated by RNG. If NB_MESSAGE = 0, it means that number of messages is infinitely.

  • the mqtt_client will get messages from the MQTT broker and print them.

Expected success behavior

  • The board IP address is printed on the HyperTerminal
  • Connection's information are printed on the HyperTerminal (broker's name, MQTT port, topic and messages received)
MQTT client connected to broker < test.mosquitto.org > at PORT:  8883
[007601] Message 01 received: TOPIC = "stm32_rng_value", MESSAGE = "6628"
[010786] Message 02 received: TOPIC = "stm32_rng_value", MESSAGE = "5742"
[011827] Message 03 received: TOPIC = "stm32_rng_value", MESSAGE = "2521"
[014780] Message 04 received: TOPIC = "stm32_rng_value", MESSAGE = "2906"
[015823] Message 05 received: TOPIC = "stm32_rng_value", MESSAGE = "7921"
[018774] Message 06 received: TOPIC = "stm32_rng_value", MESSAGE = "0535"
[019814] Message 07 received: TOPIC = "stm32_rng_value", MESSAGE = "4004"
[020852] Message 08 received: TOPIC = "stm32_rng_value", MESSAGE = "0401"
[021895] Message 09 received: TOPIC = "stm32_rng_value", MESSAGE = "7454"
[022938] Message 10 received: TOPIC = "stm32_rng_value", MESSAGE = "7653"
[023945] Empty message published at end
Client disconnected from broker < test.mosquitto.org >.
  • The green LED is toggling after successfully receiving all messages.

Error behaviors

  • The red LED is toggling to indicate any error that has occurred.

Assumptions if any

None

Known limitations

  • Since NetXDuo does not support proxy, mqtt_client should be connected directly to the server.

Notes

To make an encrypted connection with MQTT server, user should follow these steps to add an x509 certificate to the mqtt_client and use it to ensure server's authentication:

  • download certificate authority CA (in this application "mosquitto.org.der" downloaded from test.mosquitto
  • convert certificate downloaded by executing the following cmd from the file downloaded path: xxd.exe -i mosquitto.org.der > mosquitto.cert.h
  • add the converted file under the application: NetXDuo/Nx_MQTT_Client/NetXDuo/App
  • configure MOSQUITTO_CERT_FILE with your certificate name.

ThreadX usage hints

  • ThreadX uses the Systick as time base, thus it is mandatory that the HAL uses a separate time base through the TIM IPs.

  • ThreadX is configured with 1000 ticks/sec, this should be taken into account when using delays or timeouts at application. It is always possible to reconfigure it in the tx_user.h, the TX_TIMER_TICKS_PER_SECOND define, but this should be reflected in tx_initialize_low_level.S file too.

  • ThreadX is disabling all interrupts during kernel start-up to avoid any unexpected behavior, therefore all system related calls (HAL, BSP) should be done either at the beginning of the application or inside the thread entry functions.

  • ThreadX offers the tx_application_define() function, that is automatically called by the tx_kernel_enter() API. It is highly recommended to use it to create all applications ThreadX related resources (threads, semaphores, memory pools...) but it should not in any way contain a system API call (HAL or BSP).

  • Using dynamic memory allocation requires to apply some changes to the linker file. ThreadX needs to pass a pointer to the first free memory location in RAM to the tx_application_define() function, using the first_unused_memory argument. This requires changes in the linker files to expose this memory location.

    • For EWARM add the following section into the .icf file:
       place in RAM_region    { last section FREE_MEM };
    • For MDK-ARM: either define the RW_IRAM1 region in the ".sct" file or modify the line below in tx_initialize_low_level.S to match the memory region being used
        LDR r1, =|Image$$RW_IRAM1$$ZI$$Limit|
    • For STM32CubeIDE add the following section into the .ld file:
        ._threadx_heap :
    {
     . = ALIGN(8);
     __RAM_segment_used_end__ = .;
     . = . + 64K;
     . = ALIGN(8);
    } >RAM_D1 AT> RAM_D1

    The simplest way to provide memory for ThreadX is to define a new section, see ._threadx_heap above. In the example above the ThreadX heap size is set to 64KBytes. The ._threadx_heap must be located between the .bss and the ._user_heap_stack sections in the linker script. Caution: Make sure that ThreadX does not need more than the provided heap memory (64KBytes in this example). Read more in STM32CubeIDE User Guide, chapter: "Linker script".

    • The tx_initialize_low_level.S should be also modified to enable the USE_DYNAMIC_MEMORY_ALLOCATION compilation flag.

NetX Duo usage hints

For more details about the MPU configuration please refer to the AN4838

Keywords

RTOS, Network, ThreadX, NetXDuo, WiFi, MQTT, DNS, NTP, TLS, Station mode, microSD

Hardware and Software environment

  • This application runs on STM32H747xx devices.

  • This application has been tested with STMicroelectronics STM32H747I-DISCO boards Revision: MB1248-H747I-D02 and can be easily tailored to any other supported device and development board.

  • A daughter board with the WiFi module is to be plugged into the microSD card connector CN12 of the STM32H747I-DISCO board.

  • The daughterboard that was used is made up of:

    • A Murata uSD-M.2 Adapter Kit rev A (J1 position 2-3, VBAT from microSD connector)
    • The 1DX M.2 Module for the Cypress WiFi (CYW4343W)

Connect Pin 20 of STMod+ connector P2 of STM32H747I-DISCO to the uSD M.2 Adapter (J9 pin3 WL_REG_ON_HOST) that supports the Cypress device as described with the below pictures:

picture1

picture2

  • This application uses USART1 to display logs, the hyperterminal configuration is as follows:
    • BaudRate = 115200 baud
    • Word Length = 8 Bits
    • Stop Bit = 1
    • Parity = None
    • Flow control = None
    • Line endings set to LF (receive).

How to use it ?

In order to make the program work, you must do the following:

  • Open your preferred toolchain
  • Edit the file CM7/Core/Inc/cy_wifi_conf.h to enter the name of your WiFi access point (WIFI_SSID) to connect to and its password (WIFI_PASSWORD).
  • Edit the file CM7/NetXDuo/App/app_netxduo.h: define the MQTT_BROKER_NAME and NB_MESSAGE.
  • For each target configuration (Nx_MQTT_Client_wifi_CM4 first then Nx_MQTT_Client_wifi_CM7) :
    • Rebuild all files
    • Load images into target memory
  • After loading the two images, you have to reset the board in order to boot (Cortex-M7) and CPU2 (Cortex-M4) at once.
  • Run the application