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SEGGER SystemView UART-Based Recording

Real-Time Recording (Continuous Recording)

• SEGGER SystemView supports continuous recording in three ways:

  • Using J-Link based debug probe

     

    

     

    • Need J-Link based debug probe

    • ST-Link (on-board) debug probe can also be used (ST-Link firmware must first be converted to J-Link firmware by using the ST-Link reflash utility provided by SEGGER)

      However, this method has some drawbacks. Once the ST-Link is converted to J-Link firmware, we will no longer be able to debug the application using STM32 CubeIDE. So, we won't be using this method.

  • Using IP based communication

  • Using UART communication

     

    

     

    • We will be using this method since it gives us the ability to do the real-time recording as well as the application debugging using STM32 CubeIDE.

SEGGER SystemView UART-Based Recording

• Setup a UART-to-USB port since the host machine does not support UART communication.

• Setting up the Virtual COM port (VCP) communication:

  ST-LINK/V2-A (ST-LINK circuitry on STM32F407x DISCOVERY board) supports an on-board Virtual COM port on U2 pin 12 (ST-LINK_TX) and U2 pin 13 (ST-LINK_RX) but these pins are NOT connected to the USART of the STM32F407 microcontroller. This is the problem! (c.f., F446RE NUCLEO board supports on-board Virtual COM port.)

  So, we need an external USB-to-UART converter module. Any USB-to-TTL Serial Converter Adapter will do.

  Install the driver (https://ftdichip.com/drivers)

  USB-UART module pins	STM32F407x DISC board pins
  TX	RX (PA3)
  RX	TX (PA2)
  GND	GND

• Connect the board according to the pin table mentioned above, and check the Virtual COM port the serial device is connected to by using dmesg command or watch tail /var/log/syslog.

  • In my environment $\to$$\to$ ttyUSB0

• Create a Project/ThirdParty/Rec/ folder, and import segger_uart.c file provided by the lecture into the folder. This is the file is used to enable the UART-based real-time recording.

• In the Project/ThirdParty/SEGGER/Config/SEGGER_SYSVIEW_Conf.h file, add the following code:

  xxxxxxxxxx
  12
  1
  /* SEGGER_SYSVIEW_Conf.h */
  2
  /*********************************************************************
  3
  * TODO: Add your defines here.                                       *
  4
  **********************************************************************
  5
  */
  6
  
  7
  #define SEGGER_UART_REC 1
  8
  
  9
  #if (SEGGER_UART_REC == 1)
  10
      extern void HIF_UART_EnableTXEInterrupt  (void);
  11
      #define SEGGER_SYSVIEW_ON_EVENT_RECORDED(x)  HIF_UART_EnableTXEInterrupt()
  12
  #endif
  

  L7: Enabling UART-based real-time recording.

• In main.c, insert SEGGER_UART_init(500000); before calling SEGGER_SYSVIEW_Conf();. (Also, the function prototype extern void SEGGER_UART_init(uint32_t);)

  To achieve the baud rate of 500000, you need to go to the "Device Configuration Tool" $\to$$\to$ Clock Configuration, and set the HCLK(MHz) to its maximum value, 168.

  [!] Note: Configuring clock and baud rate requires some calculations. Consult the MCU Reference Manual $\to$$\to$ USART functional description $\to$$\to$ Fractional baud rate generation

  If you are to use a different HCLK(MHz), you'll have to modify the following configurations accordingly. For example if you want the HCLK to be 50 MHz and APB1 Prescalar to be 2, then update the code as follows:

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  1
  /* Project/ThirdParty/SEGGER/Rec/segger_uart.c */
  2
  
  3
  ...
  4
  #define OS_FSYS 50000000L   // MCU core frequency of Flasher ARM Pro V4
  5
  ...
  6
  #define UART_BASECLK        OS_FSYS / 2       // USART2 runs on APB1 clock
  7
  ...
  

• In main.c, comment out SEGGER_SYSVIEW_Start(); since now we want to call this function from Project/ThirdParty/Rec/segger_uart.c.

  • Don't forget this step! If you do not comment this out, you will see nothing on the SystemView window when you start recording.

• Check if #define configUSE_PREEMPTION 0 (cooperative scheduling), build the project and flash it to target.

• Open SystemView $\to$$\to$ Target $\to$$\to$ Recorder Configuration $\to$$\to$ UART

• Start recording!

Note

• SEGGER SystemView UART-based Recording may not work on the SEGGER SystemView software end at times. This is a known issue. If you have done everything correctly up to this point, don't worry and try the followings:

  1. Check the wiring

  2. Check the COM port or serial port to which the USB-to-Serial cable is connected

  3. Close the SEGGER SystemView software $\to$$\to$ Reflash the program on the target $\to$$\to$ Run the SEGGER SystemView software again $\to$$\to$ Select the correct COM port and baudrate $\to$$\to$ Run $\to$$\to$ Stop $\to$$\to$ Run a couple of times

  4. If none of these works at this point, move on to the next section. In my case, the following projects had no issue with the SEGGER SystemView UART-based Recording.

References

Nayak, K. (2022). Mastering RTOS: Hands on FreeRTOS and STM32Fx with Debugging [Video file]. Retrieved from https://www.udemy.com/course/mastering-rtos-hands-on-with-freertos-arduino-and-stm32fx/