Posted on March 26, 2012 at 05:23Hi,
I'm trying to operate the TIM2_CH1_ETR as an external event to clear OCxREF. I have configured:
1) PA0 as TIM2_CH1_ETR Alternate function and
2) PB11 as TIM2_CH4 PWM output.
I'm trying to implement what is described in Section: 13.3.11 and Fig: 99 from the STM32L Manual. The code is as below. I'm not sure what I'm missing, any help on this will be appreciated.
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
TIM_OCInitTypeDef TIM_OCInitStructure;
// Connect TIM2 PWM Output to PB11 pin
GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_TIM2);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM2);
// Enable Timer2 clock
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
// Timer2 Configuration
TIM_TimeBaseInitStruct.TIM_Prescaler = 0U;
TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInitStruct.TIM_Period = 999U;
TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStruct);
// Output Compare Structure parameters for Duty Cycle
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 450U;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC4Init(TIM2, &TIM_OCInitStructure);
TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM2, ENABLE);
// ETR_Initilize
TIM_ClearOC4Ref(TIM2, TIM_OCClear_Enable);
TIM_SelectOCREFClear(TIM2, TIM_OCReferenceClear_ETRF);
TIM_ETRConfig(TIM2, TIM_ExtTRGPSC_OFF, TIM_ExtTRGPolarity_NonInverted, 0);
TIM_Cmd(TIM2, ENABLE);
#etr
