TIM2_CH1_ETR as an external event to clear OCxREF.

mary11 · ‎2012-03-25

Posted on March 26, 2012 at 05:19

Hi,

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);