I'm tuning stm32l100
for a STANDBY mode. The MCU should woke up 2 times per second. For this I use RTC wakeup timer. But after how MCU has entered to the STANDBY mode it immediately wakes up.
If instead the STANDBY mode I use a simple sleep-mode (__WFI) all works fine.
My code is here
After the MCU is starting
a. saves flags CSR_SBF and CSR_WUF, after that clears them.
if (PWR->CSR & PWR_CSR_SBF_BIT) { // ... } if (PWR->CSR & PWR_CSR_WUF_BIT) { // ... } PWR->CR |= PWR_CR_CSBF_BIT|PWR_CR_CWUF_BIT; //while (PWR->CSR & PWR_CSR_SBF_BIT); while (PWR->CSR & PWR_CSR_WUF_BIT);
I noted that CSR_SBF never clears. If I uncomment string with
while
then MCU stall on it place. I don't understand why.b. saves reset source flags, after that clears them.
volatile uint32_t csr; csr = RCC->CSR; // .... saving // clear flags RCC->CSR |= RCC_CSR_RMVF_BIT;
After how MCU woke up from the STANDBY all reset source flags are cleared. It seems how reset sources are absent but code execute from 0x0.
Tuning RTC wakeup-timer
void rtc_set_wakeup_mode(const uint32_t wakeup_counter) { RTC_WRITE_PROTECT_DISABLE(); RTC->CR &= ~RTC_CR_WUTE_BIT; while (!(RTC->ISR & RTC_ISR_WUTWF_BIT)); RTC->WUTR = wakeup_counter; RTC->CR &= 0xfffffff7; RTC->CR |= RTC_WAKEUPCLOCK_RTCCLK_DIV2; __HAL_RTC_WAKEUPTIMER_EXTI_ENABLE_IT(); __HAL_RTC_WAKEUPTIMER_EXTI_ENABLE_RISING_EDGE(); RTC->CR |= RTC_CR_WUTIE_BIT|RTC_CR_WUTE_BIT; RTC_WRITE_PROTECT_ENABLE(); }
Enter in the STANDBY mode
void pwdm_enter_standby_mode(void) { PWR->CR |= PWR_CR_PDDS_BIT; SCB->SCR |= SCB_SCR_SLEEPDEEP_BIT; __WFI(); }
RCC->CSR
is 0x00420003 – Serge Maslyakov0x1FF80004
is0xFF870078
– Serge Maslyakov