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STM32 PWM width different pulse width and modified in another interrupt

Question asked by lopez.pedro.001 on Mar 16, 2015
Latest reply on Mar 16, 2015 by Clive One
Hi, I need to modify a PWM inside an interrupt, I though that It would be easy, just changing CCR2 to the new desired value but it is not working properly.

The change is not happening each pulse, it is a bit random.. not sure why. If i set 3000, it works right, if I set 17500 it works right, but if i set a condition to change from one to the other value then it doesnt work because it doesnt change in each interrupt, at it is even a bit random  (image below)...

My code is simple..., after each TIM5 interrupt I want a new PWM (in this example 2 values, in my real code more values, but I wanted something easy to show here)

void TIM5_IRQHandler(void) 
 if (TIM_GetITStatus(TIM5, TIM_IT_Update) != RESET)
    static int a=1;
    TIM_ClearITPendingBit(TIM5, TIM_IT_Update);


Here is the initialization of the ports (that's working right)

void TIM5_Configuration(void)
 TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

 RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);

 TIM_TimeBaseStructure.TIM_Period =5200;
 TIM_TimeBaseStructure.TIM_Prescaler = 0;
 TIM_TimeBaseStructure.TIM_ClockDivision = 0;
 TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
 TIM_TimeBaseInit(TIM5, &TIM_TimeBaseStructure);
 TIM_PrescalerConfig(TIM5, 2 , TIM_PSCReloadMode_Immediate);
 TIM_ITConfig(TIM5,TIM_IT_Update , ENABLE);

 NVIC_InitTypeDef   NVIC_InitStructure;

 NVIC_InitStructure.NVIC_IRQChannel = TIM5_IRQn;
 NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

void TIM9_PWM_Configuration2(void)
 GPIO_InitTypeDef GPIO_InitStructure;
 TIM_OCInitTypeDef  TIM_OCInitStructure;
 TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM9, ENABLE);

 GPIO_InitStructure.GPIO_Pin = pinO;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
 GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
 GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;
 GPIO_Init(portO, &GPIO_InitStructure);

 TIM_TimeBaseStructure.TIM_Period =5200*6;
 TIM_TimeBaseStructure.TIM_RepetitionCounter =0;
 TIM_TimeBaseStructure.TIM_Prescaler = 0;
 TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
 TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
 TIM_TimeBaseInit(TIM9, &TIM_TimeBaseStructure);
// TIM_PrescalerConfig(TIM9, 2 , TIM_PSCReloadMode_Immediate);
 TIM_ITConfig(TIM9,TIM_IT_Update , ENABLE);

 /* Enable TIM9 Preload register on ARR */
 TIM_ARRPreloadConfig(TIM9, ENABLE);

 /* TIM PWM1 Mode configuration */
 TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
 TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
 TIM_OCInitStructure.TIM_Pulse = 1000;
 TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 TIM_OC2Init(TIM9, &TIM_OCInitStructure);
 TIM_OC2PreloadConfig(TIM9, TIM_OCPreload_Enable);


Bank2 CH 8 is the PWM TIM 9 CH2 while Bank2 ch 15 is the IRQ (TIM 5)


I dont know if DMA + PWM would fix this problem.. I dont know if it would even work, but I though that it would be easy, a simple thing.

Any tip or help would be welcomed.

Thanks in advance.