Flash writes fail after exiting stop3 on stm32u375

[Geoffrey1]

I have an application that uses internal flash for logging.  Unfortunately, after exiting stop3 subsequent writes to flash fail.  Here’s my exit code -- the names of the routines should give a general idea.  I don’t really have a clue what changed and the reference manual is notably sparse on details about the various stop/standby/shutdown modes

 

  SET_BIT(SCB->SCR, ((uint32_t)SCB_SCR_SLEEPDEEP_Msk));

  __DSB();
  __WFI();
  __ISB();

  CLEAR_BIT(SCB->SCR, ((uint32_t)SCB_SCR_SLEEPDEEP_Msk));
  PWR->APCR &= ~PWR_APCR_APC;
  palSetLine(LINE_testpin);

  chSysLock();
  tagPowerRestoreClocksAfterStop3();
  tagPowerPostStop3WakeEventI();
  chSysUnlock();
   // Ensure Flash is awake and not stuck in low-power mode
  FLASH->ACR &= ~(FLASH_ACR_SLEEP_PD); 
  __DSB();

 

[KDJEM.1]

Hello ​@Geoffrey1;

 

First of all I apologize for my late reply.

Do you get the same issue when starting from an available example PWR_STOP3?

For more information about power consumption modes, I recommend you to look at RM0487 section 9.3.5 PWR power management and the datasheet.

 

Thank you.

Kaouthar

[KDJEM.1]

Hello ​@Geoffrey1 ,

 

Any update? 

Is the issue solved?

 

Thank you.

Kaouthar

[Geoffrey1]

Yes, but it’s been a while.  Here’s what I ended up doing (besides restarting clocks and power mode):

 

/**

* @brief Return STM32U3 flash control/status to run-ready state after Stop3.

*/

static inline void tagPowerRestoreFlashAfterStop3(void)

{MODIFY_REG(PWR->CR1, PWR_CR1_LPMS, 3U);

uint32_t acr_clear = 0U;

uint32_t sr_clear = 0U;

uint32_t sr_powerdown = 0U;

 

#if defined(FLASH_ACR_LPM)

acr_clear |= FLASH_ACR_LPM;

#endif

#if defined(FLASH_ACR_PDREQ1)

acr_clear |= FLASH_ACR_PDREQ1;

#endif

#if defined(FLASH_ACR_PDREQ2)

acr_clear |= FLASH_ACR_PDREQ2;

#endif

#if defined(FLASH_ACR_SLEEP_PD)

acr_clear |= FLASH_ACR_SLEEP_PD;

#endif

if (acr_clear != 0U) {

CLEAR_BIT(FLASH->ACR, acr_clear);

}

 

#if defined(FLASH_SR_PD1)

sr_powerdown |= FLASH_SR_PD1;

#endif

#if defined(FLASH_SR_PD2)

sr_powerdown |= FLASH_SR_PD2;

#endif

for (uint32_t timeout = 1024U;

timeout > 0U && ((FLASH->SR & sr_powerdown) != 0U);

timeout--) {

__NOP();

}

 

sr_clear = TAG_U3_FLASH_SR_ERROR_MASK;

WRITE_REG(FLASH->SR, sr_clear);

}