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Timer DMA Burst mode (arbitrary waveform)

Question asked by hellenthal.wim on Sep 22, 2017
Latest reply on Mar 5, 2018 by Aleksey Zhurkin

Dear all,


I'm having a problem creating a arbitrary waveform using timer 1, MCU STM32L476RG. I use STM32CubeMX (4.21.0) to generate all initialization code after which I try to start a DMA transfer from memory to the timer 1 peripheral. I'm partly successful doing this. 


I created a array of 6 words for two waveform patterns to be send to TIM1  channel  1  (TIM1_ARR, TIM1_RCR, TIM1_CCR1) This is how the basics look


uint32_t aSRC_Buffer[6] = { 100, 2, 15, 100, 8, 50 };  /// ARR, RCR, CCR1  x 2


HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1) ;


With this code only the first pattern is generated. changing TIM_DMABURSTLENGTH_3TRANSFERS to TIM_DMABURSTLENGTH_6TRANSFERS does not work either (seems right if my assumption is correct, see below). 


I don't understand the relation between the complete DMA buffer size (mem) and the TIM registers update. Right now I assume that setting TIM_DMABURSTLENGTH_3TRANSFERS means the three TIM registers starting at ARR are updated. But how do I set the total buffer size to use. I have tried to set  DMA1_Channel6->CNDTR = 6;  in the HAL_TIM_Base_MspInit routine but that didn't help either. I'm lost.... Is there anyone that can explain to me what I am missing here. 


some cubemx settings are :

DMA1 -> DMA1 channel 6 -> memory to peripheral -> priority high

                Mode normal      Increment address -> memory only

                Data width word


Partly generated code is



    /* Peripheral clock enable */

    hdma_tim1_up.Instance = DMA1_Channel6;
    hdma_tim1_up.Init.Request = DMA_REQUEST_7;
    hdma_tim1_up.Init.Direction = DMA_MEMORY_TO_PERIPH;
    hdma_tim1_up.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_tim1_up.Init.MemInc = DMA_MINC_ENABLE;
    hdma_tim1_up.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
    hdma_tim1_up.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
    hdma_tim1_up.Init.Mode = DMA_NORMAL;
    hdma_tim1_up.Init.Priority = DMA_PRIORITY_HIGH;
    if (HAL_DMA_Init(&hdma_tim1_up) != HAL_OK)
      _Error_Handler(__FILE__, __LINE__);
    /* TIM1 interrupt Init */
    HAL_NVIC_SetPriority(TIM1_UP_TIM16_IRQn, 0, 0);



Thanks in advance,