STM32F4 HAL RTC Library Output
It appears that if the output bit is set (RTC_CR_COE) it doesn't get cleared when the RTC is initialized.
In the library code:
HAL_StatusTypeDef HAL_RTC_Init(RTC_HandleTypeDef *hrtc)
{
...
else
{
/* Clear RTC_CR FMT, OSEL and POL Bits */
hrtc->Instance->CR &= ((uint32_t)~(RTC_CR_FMT | RTC_CR_OSEL | RTC_CR_POL));
/* Set RTC_CR register */
hrtc->Instance->CR |= (uint32_t)(hrtc->Init.HourFormat | hrtc->Init.OutPut | hrtc->Init.OutPutPolarity);
/* Configure the RTC PRER */
hrtc->Instance->PRER = (uint32_t)(hrtc->Init.SynchPrediv);
hrtc->Instance->PRER |= (uint32_t)(hrtc->Init.AsynchPrediv << 16U);
/* Exit Initialization mode */
hrtc->Instance->ISR &= (uint32_t)~RTC_ISR_INIT;
...
}
Should the above line be:
hrtc->Instance->CR &= ((uint32_t)~(RTC_CR_FMT | RTC_CR_OSEL | RTC_CR_POL | RTC_CR_COE));
Karl