Posted on March 02, 2014 at 11:57
Hi.
I downloaded to my Discovery PWM input peripheral example. I've changed it little bit to use 32-bit timer 5.
TIM5 initialization code:
GPIO_InitTypeDef GPIOA_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
/* TIM5 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
/* GPIOB clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
/* TIM5 chennel2 configuration : PA.01 */
GPIOA_InitStructure.GPIO_Pin = GPIO_Pin_1;
GPIOA_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIOA_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIOA_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIOA_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
GPIO_Init(GPIOA, &GPIOA_InitStructure);
/* Connect TIM pin to AF2 */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM5);
/* Enable the TIM5 global Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = TIM5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM5_ICInitStructure.TIM_Channel = TIM_Channel_2;
TIM5_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
TIM5_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM5_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
TIM5_ICInitStructure.TIM_ICFilter = 0x0;
TIM_PWMIConfig(TIM5, &TIM5_ICInitStructure);
/* Select the TIM5 Input Trigger: TI2FP2 */
TIM_SelectInputTrigger(TIM5, TIM_TS_TI2FP2);
/* Select the slave Mode: Reset Mode */
TIM_SelectSlaveMode(TIM5, TIM_SlaveMode_Reset);
TIM_SelectMasterSlaveMode(TIM5,TIM_MasterSlaveMode_Enable);
/* TIM enable counter */
TIM_Cmd(TIM5, ENABLE);
/* Enable the CC2 Interrupt Request */
TIM_ITConfig(TIM5, TIM_IT_CC2, ENABLE);
In readmy file is written:
TIM counter clock is 84MHz
and
Frequency = TIM counter clock / TIM4_CCR2 in Hz,
so in interrupt I've got:
Frequency = 84000000 / IC2Value;
To that moment everything work perfectly.
Problem became when I've changed prescaler to 2 so I've changed in code:
TIM5_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV2;
and, following on from that:
Frequency = 42000000 / IC2Value;
After that I should get the same frequency like before but it isn't. I've got previous frequency divided by 2. What is wrong?
Thanks
Michael
