This demo is targeted towards the Nucleo-F446RE board, with 512 kB internal Flash EEPROM and 128 kB internal RAM.

To compile the demo programs you can use the STM32CubeIDE development environment. Note that STM32CubeIDE is cross-platform. The information outlined on this page applies to both Microsoft Windows and Linux users.

To program the bootloader into the internal flash, the on-board ST-Link debugger interface was used. Firmware updates via the serial communication port are preconfigured to use the virtual COM-port offered by the ST-Link. This means that no additional hardware is needed, besides a standard micro-USB cable.

The demo programs for the Nucleo-F446RE board are specifically dedicated to showcase firmware updates via Modbus RTU. If you would like to configure firmware updates via Modbus RTU yourself, use these demo programs as a reference together with the details on this Wiki page.

The demo user program features functionality for automatic bootloader reactivation, when it detects a firmware update request. The demo user program comes with Feaser’s own MicroTBX-Modbus software stack to realize this functionality. Refer to function AppCustomFunctionCallback() in file “app.c” for details on its implementation.

Note that MicroTBX-Modbus is released under the same dual-licensing model as OpenBLT. Feel free to contact Feaser to request a quote for its commercial license.

By default, the Nucleo-F446RE demo programs are configured to firmware updates via Modbus RTU on an RS232 communication link. Specifically the virtual COM-port offered by the on-board ST-Link. The UART Rx and Tx pins are connected to the USART2 peripheral in this case. Make sure that macro BOOT_COM_MBRTU_CHANNEL_INDEX is set to 1 in “blt_conf.h”:

/** \brief Select the desired UART peripheral as a zero based index. */
#define BOOT_COM_MBRTU_CHANNEL_INDEX     (1)

The Nucleo-F446RE demo programs also support firmware updates via Modbus RTU on an RS45 communication link. To use this feature, an RS485 transceiver needs to be added. The Waveshare RS485/CAN shield was selected for this purpose.

The UART Rx and Tx pins of the RS485 transceiver are connected to the USART1 peripheral in this case. Make sure that macro BOOT_COM_MBRTU_CHANNEL_INDEX is set to 0 in “blt_conf.h”:

/** \brief Select the desired UART peripheral as a zero based index. */
#define BOOT_COM_MBRTU_CHANNEL_INDEX     (0)

Next, connect the RS485 A and B differential signals lines to your PC's USB port using a USB-RS485 converter.

Note that when using an RS485 transceiver you typically need to use a digital output to toggle its receiver / transmitter enable pin. You can implement this pin toggling in hook-function MbRtuDriverOutputControlHook() located in file “hooks.c”. Example implementation:

/************************************************************************************//**
** \brief     Controls the state of the DE/NRE GPIO pin on an RS485 transceiver.
** \param     enable When enable is BLT_TRUE, the pin should go logic high to enable the
**            driver output. When enable is BLT_FALSE, the pin should go logic low to
**            enable the receiver input.
** \return    none.
**
****************************************************************************************/
void MbRtuDriverOutputControlHook(blt_bool enable)
{
  /* Note that this only applies if the Waveshare RS485/CAN shield is installed and
   * RS485 communication is used for firmware updates via Modbus RTU.
   */
#if (BOOT_COM_MBRTU_CHANNEL_INDEX == 0)
 
  /* Should the driver output be enabled (transmit)? */
  if (enable == BLT_TRUE)
  {
    /* If needed, set DE and NRE pins to high to enable the driver output. */
    LL_GPIO_SetOutputPin(GPIOA, LL_GPIO_PIN_8);
  }
  /* The receiver output should be enabled (receive). */
  else
  {
    /* If needed, set DE and NRE pins to low to enable the receiver input. */
    LL_GPIO_ResetOutputPin(GPIOA, LL_GPIO_PIN_8);
  }
#endif
} /*** end of MbRtuDriverOutputControlHook ***/

Two demo projects are included in the OpenBLT bootloader package. One for the bootloader itself and one for the demo user program. This user program is configured such that it can be programmed, into the internal flash memory of the microcontroller, during a firmware update with the bootloader.

The first step in getting the the bootloader up-and-running, is the creation of the Eclipse workspace in STM32CubeIDE. After starting STM32CubeIDE, you are prompted to open a workspace. It is easiest to create a new one in the following directory: .\Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\

To import the demo programs into the workspace, select File → Import from the program menu. Then select General → Existing Projects into Workspace. On the next screen you select the following directory as the root directory: .\Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\. Eclipse will automatically find the Boot and Prog projects and select them:

Click the Finish button to complete the project import operation.

Before the bootloader can be used, it needs to be built and programmed into the STM32F446RE's internal flash memory. The steps in this section only need to be done once.

1. Set the project as the active project in Eclipse. This is achieved by clicking the Boot project in the Project Explorer to select it.
2. Next, right-click the Boot project in the Project Explorer and select Refresh from the popup menu.
3. Finally, right-click the Boot project in the Project Explorer and select Build Project from the popup menu to compile all the bootloader sources and link them together into the final executable.

The bootloader program is now ready to be programmed into the internal flash memory of the STM32F446RE microcontroller. Make sure the Nucleo-F446REboard is connected to your PC via a USB cable. Next, select Run → Debug from the menu to flash the bootloader program. This will launch the Debug perspective in Eclipse. Once done, you can start the bootloader program by selecting Run → Resume from the menu.

Alternatively, you can use your favorite programmer to flash the bootloader using one of the following files, depending on what file type your programmer supports:

• \Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\Boot\Debug\openblt_stm32f446.elf
• \Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\Boot\Debug\openblt_stm32f446.srec

1. Set the project as the active project in Eclipse. This is achieved by clicking the Prog project in the Project Explorer to select it.
2. Next, right-click the Prog project in the Project Explorer and select Refresh from the popup menu.
3. Finally, right-click the Prog project in the Project Explorer and select Build Project from the popup menu to compile all the user program sources and link them together into the final executable.

The output file is

• \Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\Prog\Debug\demoprog_stm32f446.srec

To download the demo program \Target\Demo\ARMCM4_STM32F4_Nucleo_F446RE_CubeIDE\Prog\Debug\demoprog_stm32f446.srec using the bootloader, follow the instructions in the following links, depending on the communication interface you intend to use:

• Firmware updates using the Modbus RTU communication interface