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STM32F4 DMA and Timer Duty cycles

Question asked by nain.haseeb on Jun 24, 2016
Latest reply on Jun 24, 2016 by markt

I am working on a personal project and keep running into a problem. The I am trying to use the DMA in an STM32F4 to control a strip of LEDs that rely on the duty cycle of an output signal.

I want to update the duty cycle of TIM5 at the end of each TIM5 period, I want to create a timer with a repeating duty cycle pattern (ie. 10% 20% 30% 10% 20% 30%...).

Is there something I am missing in my code in order to get that functionality?


void ws2811LedStripHardwareInit(void)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    DMA_InitTypeDef DMA_InitStructure;
     TIM5->CCR2 = 106;
    uint16_t prescalerValue;


    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);


     
    /* GPIOA Configuration: TIM5 Channel 1 as alternate function push-pull */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);


    GPIO_PinAFConfig(GPIOA, GPIO_PinSource0,  GPIO_AF_TIM5);




    // Stop timer
    TIM_Cmd(TIM5, DISABLE);


    /* Compute the prescaler value */
    prescalerValue = (uint16_t) (SystemCoreClock / 2 / 84000000) - 1;
    /* Time base configuration */
    TIM_TimeBaseStructure.TIM_Period = 104; // 800kHz
    TIM_TimeBaseStructure.TIM_Prescaler = prescalerValue;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM5, &TIM_TimeBaseStructure);


    /* PWM1 Mode configuration: Channel1 */
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM5, &TIM_OCInitStructure);
    TIM_OC1PreloadConfig(TIM5, TIM_OCPreload_Enable);


     
    TIM_Cmd(TIM5, ENABLE);




    /* configure DMA */
    /* DMA1 Channel Config */
    DMA_Cmd(DMA1_Stream2, DISABLE);            // disable DMA channel 6
    DMA_DeInit(DMA1_Stream2);
    DMA_StructInit(&DMA_InitStructure);
    DMA_InitStructure.DMA_Channel = DMA_Channel_6;
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&(TIM5->CCR1);
    DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)ledStripDMABuffer;
    DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
    DMA_InitStructure.DMA_BufferSize = WS2811_DMA_BUFFER_SIZE;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;
    DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_1QuarterFull;
    DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
    DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
    DMA_Init(DMA1_Stream2, &DMA_InitStructure);


    DMA_ITConfig(DMA1_Stream2, DMA_IT_TC, ENABLE);
    DMA_ClearITPendingBit(DMA1_Stream2, DMA_IT_TCIF2);               // clear DMA1 Channel 6 transfer complete flag


    NVIC_InitTypeDef NVIC_InitStructure;


    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = NVIC_PRIORITY_BASE(NVIC_PRIO_WS2811_DMA);
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = NVIC_PRIORITY_SUB(NVIC_PRIO_WS2811_DMA);
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);


    setStripColor(&hsv_white);
    ws2811UpdateStrip();
     
     //sets LED strip to white, duty cycle of 68%
     //TIM5->CCR1 = 72;
}

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