lucasdietrich / azure-rtos-mqtt-nucleo-f429zi

Azure RTOS MQTT client demo for Nucleo F429ZI board. Generated with SMT32CubeMX.

Nx_MQTT_Client 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.

The main entry function tx_application_define() is called by ThreadX during kernel start, at this stage, all NetX resources are created.

• A NX_PACKET_POOL is allocated

• A NX_IP instance using that pool is initialized

• The ARP, ICMP and protocols (TCP and UDP) are enabled for the NX_IP instance

• A DHCP client is created.

The application then creates 2 threads with different priorities:

• AppMainThread (priority 10, PreemtionThreashold 10) : created with the TX_AUTO_START flag to start automatically.

• AppMQTTClientThread (priority 5, PreemtionThreashold 5) : created with the TX_DONT_START flag to be started later.

The AppMainThread starts and perform the following actions:

• starts the DHCP client

• waits for the IP address resolution

• resumes the AppMQTTClientThread

The AppMQTTClientThread, once started:

• creates a dns_client with USER_DNS_ADDRESS used as DNS server then get MQTT broker address from MQTT_BROKER_NAME predefined on app_netxduo.h.

• creates an mqtt_client

• connects mqtt_client to the online MQTT broker; connection with server will be secure and a tls_setup_callback will set TLS parametres. By default MQTT_PORT for encrypted mode is 8883.

    refer to note 4 below, to know how to setup an x509 certificate.
  

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

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

• 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 :
Message 1 received: TOPIC = Temperature, MESSAGE = 34
Message 2 received: TOPIC = Temperature, MESSAGE = 35
Message 3 received: TOPIC = Temperature, MESSAGE = 35
Message 4 received: TOPIC = Temperature, MESSAGE = 34
Message 5 received: TOPIC = Temperature, MESSAGE = 33
client disconnected from server

• 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

• The Application is using the DHCP to acquire IP address, thus a DHCP server should be reachable by the board in the LAN used to test the application.

• The application is configuring the Ethernet IP with a static predefined MAC Address, make sure to change it in case multiple boards are connected on the same LAN to avoid any potential network traffic issues.

• The MAC Address is defined in the main.c

void MX_ETH_Init(void)
{

   /* USER CODE BEGIN ETH_Init 0 */

  /* USER CODE END ETH_Init 0 */

   static uint8_t MACAddr[6];

  /* USER CODE BEGIN ETH_Init 1 */

  /* USER CODE END ETH_Init 1 */
  heth.Instance = ETH;
  heth.Init.AutoNegotiation = ETH_AUTONEGOTIATION_ENABLE;
  heth.Init.Speed = ETH_SPEED_100M;
  heth.Init.DuplexMode = ETH_MODE_FULLDUPLEX;
  heth.Init.PhyAddress = LAN8742A_PHY_ADDRESS;
  MACAddr[0] = 0x00;
  MACAddr[1] = 0x80;
  MACAddr[2] = 0xE1;
  MACAddr[3] = 0x00;
  MACAddr[4] = 0x00;
  MACAddr[5] = 0x00;

Known limitations

• Default NX_DNS_MAX_RETRIES value in "nx_user.h" may not work with some MQTT servers, they should be tuned for example:

  #define NX_DNS_MAX_RETRIES 10

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

Notes

1. 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 100 ticks/sec by default, 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 require 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_low_level_initilize.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" flag.

Keywords

RTOS, Network, ThreadX, NetXDuo, MQTT, TLS, UART

Hardware and Software environment

• This application runs on STM32F429xx devices

• This application has been tested with STMicroelectronics STM32F429ZI Nucleo boards Revision MB1137 B-01 and can be easily tailored to any other supported device and development board.

• This application uses USART3 to display logs, the hyperterminal configuration is as follows:

  • BaudRate = 115200 baud
  • Word Length = 8 Bits
  • Stop Bit = 1
  • Parity = none
  • Flow control = None

How to use it ?

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

• Open your preferred toolchain
• Edit the file app_netxduo.h : define the USER_DNS_ADDRESS, the MQTT_BROKER_NAME and NB_MESSAGE.
• Rebuild all files and load your image into target memory
• Run the application