How to update STM32 Firmware OTA

This is the 4^th tutorial in the STM32 Ethernet series using Mongoose Library. In the previous tutorial, we learned how to use the mongoose wizard to create a web UI. We also saw how to connect the different elements of the UI with STM32 peripherals for functional integration.

Today in this tutorial we will see how to use the Mongoose Library and Mongoose Wizard to update the Firmware on STM32 Over The Air (OTA). I will create 2 projects in this tutorial. The Project1 will have a simple UI with an element to update the firmware. Whereas the Project2 will contain 2 pages. Page1 will contain elements to control the LEDs on STM32 dev board and Page2 will contain an element to update the firmware.

Project 1

Create the UI

I have already explained how to create the WebUI In the previous tutorial, So I will skip explaining every detail here. Let’s just focus on the elements and their APIs.

Below is the image showing the UI for the Project 1.

There is only a single panel containing a button to choose the .bin file. This is the Firmware Update button added from the UI elements as shown below.

The REST API for this button is automatically created. Below is the image showing the API for the firmware_update Button.

The API name is firmware_update and the type is ota. The functions generated by the mongoose wizard will be used to update the firmware on the device, so we do not need to modify anything from our end.

There is nothing more to modify on the wizard, so we will generate the project.

CubeIDE Configuration

We don’t need to modify anything in the cubeIDE as well. The IDE does not generate the binary file by default, so we will enable it in the properties.

Go to Project Properties -> C/C++ Build -> Settings -> Post Build Outputs and enable the binary file generation as shown in the image below.

Once the project is build, the binary file will generate in the project -> Debug folder. We can flash this binary file from the webUI.

Run the Project

Flash this project to the board and check the logs on the serial console. Below is the image showing the logs on the serial terminal.

You can see in the image above, the DHCP sent the request for the IP. Afterwards it got the IP 192.168.1.3. We can now open this IP address in our browser. Below is the image showing the webUI responding to the IP address.

Project 2

Project 2 will contain more elements in the UI to control the LEDs on the dev board. We also need to configure the pins in the cubeMX. This is to demonstrate that we can even modify the project as per our requirement and still use the mongoose OTA update.

Create the UI

I have already explained how to create the WebUI In the previous tutorial, So I will skip explaining every detail here. Let’s just focus on the elements and their APIs.

Below is the image showing the UI for the Project 2.

The UI contains 2 pages. The Page 1 has the toggle buttons to control the LEDs on the dev board. Page 2 contains the element to update the firmware Over The Air.

Below is the image showing the details about the LED Control Panel on Page 1.

The text filed contains a fixed text (LED1) and the variable text. The variable text part will fetch the value of the state variable from the API (leds.state). If this value is a 1 (true), we will set the text ON, otherwise set the text OFF, ${leds.state ? ‘ON’:’OFF’}.

The REST API for the LED Toggle button is shown in the image below.

Below is the image showing the details about the BackLight Control Panel on Page 1.

The text filed contains the variable text. We will fetch the value of the state variable from the API (BCKLT.state). If this value is a 1 (true), we will set the text Enabled, otherwise set the text Disabled, ${BCKLT.state ? ‘Enabled’ : ‘Disabled’}.

The REST API for the BCKLT Toggle button is shown in the image below.

Page 2 only contains the element to update the Firmware. It consists of the text (Firmware Update) and the OTA button. Below is the image showing the Element on Page 2.

The API variable (firmware_update) for the ota button is assigned automatically. We do not need to modify anything here.

CubeMX Configuration

We need to configure the pins for the LED and the Display Backlight. We will do this in the cubeMX.

Below is the image showing the configuration for the LED pin PJ2.

The Pin PJ2 is configured in the output mode. Since I am using a dual core dev board, I need to assign the pin to cortex M7 core.

The Display Backlight is connected to the pin PK0. We also need to configure this pin in the output mode. Below is the image showing the configuration for the pin PK0.

The Code

The LED and Backlight control functions are pre-generated in the mongoose_glue.c file. This file regenerates each time the mongoose dashboard is updated. Hence it is always better to write getter and setter functions in some other file (like main.c).

Below are the getter and setter functions for the LED control.

void my_get_leds(struct leds *data) {
  if (HAL_GPIO_ReadPin(GPIOJ, GPIO_PIN_2)) data->state = 0;  // LED is OFF
  else data->state = 1;  // LED is ON
}
void my_set_leds(struct leds *data) {
  if (data->state) HAL_GPIO_WritePin(GPIOJ, GPIO_PIN_2, GPIO_PIN_RESET);  // turn LED ON
  else HAL_GPIO_WritePin(GPIOJ, GPIO_PIN_2, GPIO_PIN_SET);  // turn LED OFF
}

The function my_get_leds will be called by the UI whenever it wants to fetch the status of the LED Pin. Here we will first read the pin PJ2. If the pin is set, that means the LED must be OFF, so we will assign the value 0 to the state variable of the API. Otherwise the LED must be ON, so we will assign the value 1 to the variable.

The function my_set_leds will be called by the UI whenever the toggle button is modified. Here we will read the state variable of the API. If this variable has the value 1, means that the toggle button is set to true, we will turn the LED ON by Resetting the pin PJ2. Otherwise the toggle button is set to false, so we will turn the LED OFF by Setting the pin PJ2.

Note that Setting and Resetting the pin has an alternate behaviour with turning the LED OFF or ON. This is due to the connection of the LED on the dev board. The LED is connected between 3.3V and the pin PJ2. Hence when the pin is Reset, the LED turns ON and when the pin is Set, the LED turns OFF. This is shown in the image below.

Similarly, the getter and setter functions for the Backlight Control are shown below.

void my_get_BCKLT(struct BCKLT *data) {
  data->state = HAL_GPIO_ReadPin(GPIOK, GPIO_PIN_0);
}
void my_set_BCKLT(struct BCKLT *data) {
  HAL_GPIO_WritePin(GPIOK, GPIO_PIN_0, data->state);
}

The LCD Backlight is connected to pin PK0. Hence here we will take a direct approach to control the backlight. The backlight turns OFF by resetting the pin PK0 and it turns ON by setting the pin. Therefore we can directly pass the value of the API Variable (data->state) to the HAL functions.

We have created getter and setter functions for the LED controls but by default, the mongoose will use the functions it generated in the mongoose_glue.c file. In order to enable the mongoose to use our custom functions, we need to set the HTTP handlers for the APIs.

  /* USER CODE BEGIN 2 */
  mongoose_init();
  mongoose_set_http_handlers("leds", my_get_leds, my_set_leds);  // add this
  mongoose_set_http_handlers("BCKLT", my_get_BCKLT, my_set_BCKLT);  // add this
  for (;;) {
    mongoose_poll();
  }
  /* USER CODE END 2 */

We can do this after the mongoose_init() function. The function mongoose_set_http_handlers will assign our custom getter (my_get_leds) and setter (my_set_leds) functions to the provided API Endpoint (leds).

CubeIDE Configuration

We don’t need to modify anything in the cubeIDE as well. The IDE does not generate the binary file by default, so we will enable it in the properties.

Go to Project Properties -> C/C++ Build -> Settings -> Post Build Outputs and enable the binary file generation as shown in the image below.

Once the project is build, the binary file will generate in the project -> Debug folder. We can flash this binary file from the webUI.

Working

We have flashed the project 1 to the dev board and the server is already running on it.

Click on the ota button and choose the project2.bin file. You can see the update logs in the serial console. Once the project is flashed, the board will reboot and the updated project will be loaded automatically.

Below is the image showing the project 2 running on the dev board.