I am using the LPTIM3 with LSE
An external input is used to trigger a capture.
The STM32U575 spends most of the time in STOP MODE 2.
To keep the LSE active in the LPTIM use the following instruction:
_HAL_RCC_LPTIM3_CLKAM_ENABLE(); // SET_BIT(RCC->SRDAMR , RCC_SRDAMR_LPTIM3AMEN)
The above statement works in the sense that the LPTIM3 continues its count in STOP MODE 2, but does not update the value of the capture register:
capture_new = LPTIM3->CCR1; // CCR1 doesn't get updates while the STM32 is in STOP MODE 2
I am missing another register to activate compare/capture module on stop mode?
void MX_LPTIM3_Init(void)
{
/* USER CODE BEGIN LPTIM3_Init 0 */
/* USER CODE END LPTIM3_Init 0 */
LPTIM_IC_ConfigTypeDef sConfig = {0};
/* USER CODE BEGIN LPTIM3_Init 1 */
/* USER CODE END LPTIM3_Init 1 */
hlptim3.Instance = LPTIM3;
hlptim3.Init.Clock.Source = LPTIM_CLOCKSOURCE_APBCLOCK_LPOSC;
hlptim3.Init.Clock.Prescaler = LPTIM_PRESCALER_DIV1;
hlptim3.Init.Trigger.Source = LPTIM_TRIGSOURCE_SOFTWARE;
hlptim3.Init.Period = 65535;
hlptim3.Init.UpdateMode = LPTIM_UPDATE_IMMEDIATE;
hlptim3.Init.CounterSource = LPTIM_COUNTERSOURCE_INTERNAL;
hlptim3.Init.Input1Source = LPTIM_INPUT1SOURCE_GPIO;
hlptim3.Init.Input2Source = LPTIM_INPUT2SOURCE_GPIO;
hlptim3.Init.RepetitionCounter = 0;
if (HAL_LPTIM_Init(&hlptim3) != HAL_OK)
{
Error_Handler();
}
sConfig.ICInputSource = LPTIM_IC1SOURCE_GPIO;
sConfig.ICPrescaler = LPTIM_ICPSC_DIV1;
sConfig.ICPolarity = LPTIM_ICPOLARITY_RISING_FALLING;
sConfig.ICFilter = LPTIM_ICFLT_CLOCK_DIV1;
if (HAL_LPTIM_IC_ConfigChannel(&hlptim3, &sConfig, LPTIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN LPTIM3_Init 2 */
__HAL_RCC_LPTIM3_CLKAM_ENABLE();
/* USER CODE END LPTIM3_Init 2 */
}
