STM32 flashing disabled after flashing a code without R/W protection

Question

I have some experience of StdPeriph libraries usage for programming stm32. But now I tried STM32Cube HAL with STM32CubeMX code generator. I generated a project with this options:

• Middleware: FreeRTOS and FatFS via SDIO
• Compiler is GCC
• stm32f103ret6 MCU

I imported generated code to Eclipse environment. I made a binary and flashed it with "st-flash write ..." as usual. My test program successfuly wrote to USART1 "Hello" in cycle - this is no problem. But then, when I tried to flash another code, it failed with "unknown chip id". If I manually connect NRST to GND, st-flash gives:

...Flash: 0 bytes (0 KiB) in pages of 2048 bytes

Full output:

2015-06-14T16:07:29 INFO src/stlink-common.c: Loading device parameters....
2015-06-14T16:07:29 INFO src/stlink-common.c: Device connected is: F1 High-density device, id 0x10036414
2015-06-14T16:07:29 INFO src/stlink-common.c: SRAM size: 0x10000 bytes (64 KiB), Flash: 0 bytes (0 KiB) in pages of 2048 bytes

I tried to use ST-Link Utility from Windows, but it cannot connect to this MCU to change option bytes (connection to another devices with stm32 works well). I tried to flash through USART1, but it failed.

Source code I flashed, of course, does not contain any read/write protection enabling. I tried 2 another MCU, but this error was reproduced.

How can I unbrick by MCUs and flash anything?

Answer 1

I found a root cause!

This is a HAL initialization function, generated by STM32CubeMX:

void HAL_MspInit(void)
{
  /* USER CODE BEGIN MspInit 0 */

  /* USER CODE END MspInit 0 */

  __HAL_RCC_AFIO_CLK_ENABLE();

  HAL_NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_4);

  /* System interrupt init*/
/* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);

    /**DISABLE: JTAG-DP Disabled and SW-DP Disabled 
    */
  __HAL_AFIO_REMAP_SWJ_DISABLE();

  /* USER CODE BEGIN MspInit 1 */

  /* USER CODE END MspInit 1 */
}

I didn't notice this simple lines!

/**DISABLE: JTAG-DP Disabled and SW-DP Disabled 
*/
__HAL_AFIO_REMAP_SWJ_DISABLE();

This macros totally disables SWD and JTAG programming, look at stm321xx_hal_gpio_ex.h:

#define __HAL_AFIO_REMAP_SWJ_DISABLE()  MODIFY_REG(AFIO->MAPR, AFIO_MAPR_SWJ_CFG, AFIO_MAPR_SWJ_CFG_DISABLE) 

I didn't found any checkbox in CubeMX to disable/enable SWD/JTAG, so this is the only behavior of code generator! Pay attention to this point when using STM32CubeMX!

Answer 2

If you set the pin assignments for the JTAG/SWD pins correctly (e.g. SYS_JTDI, SYS_JTDO-TRACESWO, etc.) on the pinout tab of STM32CubeMX, the generated code will not disable JTAG/SWD.