Posted on June 28, 2013 at 21:28 Hello, Could somebody please explain why the code below (AN4099) does configure alternate function 2 for TIM2 (capture/compare channel 2) and yet configured channel 1 as well as an interrupt source? If it is desired to measure a signal low or high time, would you not expect one channel to be programmed as capturing both rising and falling edge? Thanks in advance! void SIRC_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
TIM_ICInitTypeDef TIM_ICInitStructure; /* Clock Configuration for TIMER */
RCC_APB1PeriphClockCmd(IR_TIM_CLK, ENABLE);
/* Enable Button GPIO clock */
RCC_AHBPeriphClockCmd(IR_GPIO_PORT_CLK, ENABLE); /* Pin configuration: input floating */
GPIO_InitStructure.GPIO_Pin = IR_GPIO_PIN;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(IR_GPIO_PORT, &GPIO_InitStructure); GPIO_PinAFConfig(IR_GPIO_PORT, IR_GPIO_SOURCE, GPIO_AF_2); /* Enable the TIM global Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = IR_TIM_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure); /* TIMER frequency input */
TIM_PrescalerConfig(IR_TIM, TIM_PRESCALER, TIM_PSCReloadMode_Immediate);
/* TIM configuration */
TIM_ICInitStructure.TIM_Channel = IR_TIM_Channel;
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter = 0x0;
TIM_PWMIConfig(IR_TIM, &TIM_ICInitStructure);
/* Timer Clock */
TIMCLKValueKHz = TIM_GetCounterCLKValue()/1000;
/* Select the TIM Input Trigger: TI2FP2 */
TIM_SelectInputTrigger(IR_TIM, TIM_TS_TI2FP2);
/* Select the slave Mode: Reset Mode */
TIM_SelectSlaveMode(IR_TIM, TIM_SlaveMode_Reset);
/* Enable the Master/Slave Mode */
TIM_SelectMasterSlaveMode(IR_TIM, TIM_MasterSlaveMode_Enable);
/* Configures the TIM Update Request Interrupt source: counter overflow */
TIM_UpdateRequestConfig(IR_TIM, TIM_UpdateSource_Regular); IRTimeOut = TIMCLKValueKHz * SIRC_TIME_OUT_US/1000;
/* Set the TIM auto-reload register for each IR protocol */
IR_TIM->ARR = IRTimeOut; /* Clear update flag */
TIM_ClearFlag(IR_TIM, TIM_FLAG_Update);
/* Enable TIM Update Event Interrupt Request */
TIM_ITConfig(IR_TIM, TIM_IT_Update, ENABLE);
/* Enable the CC2/CC1 Interrupt Request */
TIM_ITConfig(IR_TIM, TIM_IT_CC2, ENABLE);
TIM_ITConfig(IR_TIM, TIM_IT_CC1, ENABLE);
/* Enable the timer */
TIM_Cmd(IR_TIM, ENABLE);
