STM32L4+: RTC Calib Out (PB2) and RTC Timestamp Input (PC13) at the same time?

PK.2 · ‎2020-06-26

Hello everybody,

i have a problem with the RTC Calib Out (1Hz) on PB2 and TimeStamp Input PC13 (Board: NUCLEO-L4R5ZI).

PPS (1 Hz clock) should be on PB2 (RTC_Calib_Out) for time synchronization with other chips.
PC13 should be configured as TimeStamp Input for events (e.g. 1 Hz)

Calib Out on PB2

With the following code works the calib out pin fine.

hrtc.Instance = RTC;
hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
hrtc.Init.AsynchPrediv = 127;
hrtc.Init.SynchPrediv = 255;
hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_POS1;
hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
HAL_RTC_Init(&hrtc);
 
HAL_RTCEx_SetCalibrationOutPut(&hrtc, RTC_CALIBOUTPUT_1HZ);

HAL_StatusTypeDef HAL_RTCEx_SetCalibrationOutPut(RTC_HandleTypeDef *hrtc, uint32_t CalibOutput)
{
  __HAL_LOCK(hrtc); 
  hrtc->State = HAL_RTC_STATE_BUSY;
  __HAL_RTC_WRITEPROTECTION_DISABLE(hrtc); 
 
  hrtc->Instance->CR &= (uint32_t)~RTC_CR_COSEL;   /* Clear flags before config */
  hrtc->Instance->CR |= (uint32_t)CalibOutput;   /* Configure the RTC_CR register */
 
  __HAL_RTC_CALIBRATION_OUTPUT_ENABLE(hrtc); // ((hrtc)->Instance->CR |= ((0x1UL << (23U))))
 
  __HAL_RTC_WRITEPROTECTION_ENABLE(hrtc);   
  hrtc->State = HAL_RTC_STATE_READY; 
  __HAL_UNLOCK(hrtc);
 
  return HAL_OK;
}

TimeStamp Input on PC13

Is only only the TimeStamp function configured, then it works also as expected. Blue is a clock with e.g. 1 Hz and the red signal is a gpio which will be toggled by the TimeStamp callback function. It works also as expected.

hrtc.Instance = RTC;
hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
hrtc.Init.AsynchPrediv = 127;
hrtc.Init.SynchPrediv = 255;
hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_POS1;
hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
HAL_RTC_Init(&hrtc);
 
HAL_RTCEx_SetTimeStamp_IT(&hrtc, RTC_TIMESTAMPEDGE_RISING, RTC_TIMESTAMPPIN_DEFAULT); // default PC13

HAL_StatusTypeDef HAL_RTCEx_SetTimeStamp_IT(RTC_HandleTypeDef *hrtc, uint32_t TimeStampEdge, uint32_t RTC_TimeStampPin)
{
  uint32_t tmpreg;
 
  __HAL_LOCK(hrtc);
  hrtc->State = HAL_RTC_STATE_BUSY;
 
  /* Get the RTC_CR register and clear the bits to be configured */
  tmpreg = (uint32_t)(hrtc->Instance->CR & (uint32_t)~(RTC_CR_TSEDGE | RTC_CR_TSE));
 
  tmpreg |= TimeStampEdge;
 
  /* Disable the write protection for RTC registers */
  __HAL_RTC_WRITEPROTECTION_DISABLE(hrtc);
 
  /* Configure the Time Stamp TSEDGE and Enable bits */
  hrtc->Instance->CR = (uint32_t)tmpreg;
 
  __HAL_RTC_TIMESTAMP_ENABLE(hrtc);
 
  /* Enable IT timestamp */
  __HAL_RTC_TIMESTAMP_ENABLE_IT(hrtc, RTC_IT_TS);
 
  /* RTC timestamp Interrupt Configuration: EXTI configuration */
  __HAL_RTC_TAMPER_TIMESTAMP_EXTI_ENABLE_IT();
  __HAL_RTC_TAMPER_TIMESTAMP_EXTI_ENABLE_RISING_EDGE();
 
  __HAL_RTC_WRITEPROTECTION_ENABLE(hrtc);
  hrtc->State = HAL_RTC_STATE_READY;
  __HAL_UNLOCK(hrtc);
 
  return HAL_OK;
}

Both together (doesn't work)

If I try both together, the calib out will work, but I won't get any TimeStamp events anymore. The signal at the TS input has only a voltage of 1.4 volts. Only the COE and COSEL bits are changed by the pin calib out. What happens here?

hrtc.Instance = RTC;
hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
hrtc.Init.AsynchPrediv = 127;
hrtc.Init.SynchPrediv = 255;
hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_POS1;
hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
HAL_RTC_Init(&hrtc);
 
HAL_RTCEx_SetTimeStamp_IT(&hrtc, RTC_TIMESTAMPEDGE_RISING, RTC_TIMESTAMPPIN_DEFAULT); // default PC13
 
HAL_RTCEx_SetCalibrationOutPut(&hrtc, RTC_CALIBOUTPUT_1HZ);

Can someone explain what changes to PC13 when the COE bit is set to 1?

waclawek.jan · ‎2020-09-01

Thanks, Imen.

JW