stm32g0 timer input capture division does not work

[Bigdan]

Hello!

Using TIM1 for pwm input capture.

Works OK for trigger prescaler 1 (default).

Want to use prescaler 4, but it doesn't work. Capture value the same as prescaler 1.

 

Timer config:

void FC_SERVO_1_TIM1_Init(void)
{

	// USER CODE END TIM1_MspInit
	GPIO_InitTypeDef GPIO_InitStruct = {0};
	/* TIM1 clock enable */
	__HAL_RCC_TIM1_CLK_ENABLE();
	__HAL_RCC_GPIOA_CLK_ENABLE();
	/**TIM1 GPIO Configuration
	PA8 ------> TIM1_CH1
	*/
	GPIO_InitStruct.Pin = GPIO_PIN_8;
	GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
	GPIO_InitStruct.Pull = GPIO_NOPULL;
	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
	GPIO_InitStruct.Alternate = GPIO_AF2_TIM1;
	HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

	/* TIM1 interrupt Init */
	HAL_NVIC_SetPriority(TIM1_CC_IRQn, 0, 0);
	HAL_NVIC_EnableIRQ(TIM1_CC_IRQn);
 // --------------------

 TIM_ClockConfigTypeDef sClockSourceConfig = {0};
 TIM_SlaveConfigTypeDef sSlaveConfig = {0};
 TIM_IC_InitTypeDef sConfigIC = {0};
 TIM_MasterConfigTypeDef sMasterConfig = {0};

 /* USER CODE BEGIN TIM1_Init 1 */

 /* USER CODE END TIM1_Init 1 */
 htim1.Instance = TIM1;
 htim1.Init.Prescaler = 15;
 htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim1.Init.Period = 65535;
 htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim1.Init.RepetitionCounter = 0;
 htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
 {
	Error_Handler();
 }
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)
 {
	Error_Handler();
 }
 if (HAL_TIM_IC_Init(&htim1) != HAL_OK)
 {
	Error_Handler();
 }
 sSlaveConfig.SlaveMode = TIM_SLAVEMODE_RESET;
 sSlaveConfig.InputTrigger = TIM_TS_TI1FP1;
 sSlaveConfig.TriggerPolarity = TIM_INPUTCHANNELPOLARITY_RISING;
 sSlaveConfig.TriggerPrescaler = TIM_ICPSC_DIV4;
 sSlaveConfig.TriggerFilter = 0;
 if (HAL_TIM_SlaveConfigSynchro(&htim1, &sSlaveConfig) != HAL_OK)
 {
	Error_Handler();
 }
 sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_RISING;
 sConfigIC.ICSelection = TIM_ICSELECTION_DIRECTTI;
 sConfigIC.ICPrescaler = TIM_ICPSC_DIV4;
 sConfigIC.ICFilter = 0;
 if (HAL_TIM_IC_ConfigChannel(&htim1, &sConfigIC, TIM_CHANNEL_1) != HAL_OK)
 {
	Error_Handler();
 }
 sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_FALLING;
 sConfigIC.ICSelection = TIM_ICSELECTION_INDIRECTTI;
 if (HAL_TIM_IC_ConfigChannel(&htim1, &sConfigIC, TIM_CHANNEL_2) != HAL_OK)
 {
	Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterOutputTrigger2 = TIM_TRGO2_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
 {
	Error_Handler();
 }

}

void TIM1_CC_IRQHandler(void)
{
 HAL_TIM_IRQHandler(&htim1);
}

 

[TDK]

You say it works with 1, but not 4, but the code shows it at 15.

No code actually reads the value. How do you determine it "doesn't work"?

 

I assure you the timer works with a prescaler of 1, and 4, and 15. So the bug has to be somewhere else--in your code somewhere.

[Bigdan]

I'm not about 

htim1.Init.Prescaler = 15;

Yes it's works OK.

I'm about 

 sSlaveConfig.TriggerPrescaler = TIM_ICPSC_DIV4;

 sConfigIC.ICPrescaler = TIM_ICPSC_DIV4;

I'm 

void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim) {
	if (htim->Instance == TIM1) {
		if(htim->Channel == HAL_TIM_ACTIVE_CHANNEL_1){
			tim1_trig_time = HAL_GetTick();
			if(tim1_isFistCaptured == 0){
				tim1_isFistCaptured=1;
			} else {
				tim1_period = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_1);
				tim1_isFistCaptured=0;
			}
			tim1_duty = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_2);
			__HAL_TIM_SET_COUNTER(htim, 0);
		}
	}
}

tim1_period and tim1_duty does not change after switch from TIM_ICPSC_DIV1 to TIM_ICPSC_DIV4

 

[TDK]

The input prescaler shouldn't substantially affect duty cycle or period. It is used to perform the IC comparison every X cycles  (prescaler > 0) instead of every cycle (prescaler = 0, default).

[Bigdan]

AS I understand and It's show in https://www.youtube.com/watch?v=P6211ic2N_s&list=PLfIJKC1ud8gjLZBzjE3kKBMDEH_lUc428&index=2&ab_channel=ControllersTech

 

TIM_ICPSC_DIV4 will trigger interrupt every fourth rising edge of input signal, not every one.

So for this time timer wii count 4 times more.

I want to reduse timer interrupts. 

[TDK]

I think you're right. I was mixing up filter and prescaler. I may take a closer look later.

 

Apologies for the noise.

[waclawek.jan]

The capture divider applies only to the capture itself, i.e. not to the TI1FP1 signal which is input to the slave-mode controller. Thus, the slave-mode controller resets the counter upon every riding edge and so the capture captures duration of the last of the 4 periods.

JW