STM32L1 PWM mit DMA falsche Periodendauer

void vInitPWM(void) {

     GPIO_InitTypeDef GPIO_InitStructure;

     TIM_TimeBaseInitTypeDef TimerInitStructure;

     TIM_OCInitTypeDef OutputChannelInit;

     NVIC_InitTypeDef NVIC_InitStructure;

     // GPIO

     RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);

     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;

     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

     GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

     GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;

     GPIO_Init(GPIOB, &GPIO_InitStructure);

     GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_TIM2);

     // TIMER

     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

     TimerInitStructure.TIM_Prescaler = 0;

     TimerInitStructure.TIM_CounterMode = TIM_CounterMode_Up;

     TimerInitStructure.TIM_Period = 0xFFFF;

     TimerInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;

     TIM_TimeBaseInit(TIM2, &TimerInitStructure);

     //PWM CHANNEL

     OutputChannelInit.TIM_OCMode = TIM_OCMode_PWM1;

     OutputChannelInit.TIM_Pulse = 0;

     OutputChannelInit.TIM_OutputState = TIM_OutputState_Enable;

     OutputChannelInit.TIM_OCPolarity = TIM_OCPolarity_Low;

     TIM_OC4Init(TIM2, &OutputChannelInit);

     TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Enable);

     TIM_ARRPreloadConfig(TIM2, ENABLE);

     TIM_CCxCmd(TIM2, TIM_Channel_4, TIM_CCx_Enable);

     TIM_Cmd(TIM2, ENABLE);

     // DMA

     RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

     TIM_DMACmd(TIM2, TIM_DMA_CC4, ENABLE);

     DMA_ITConfig(DMA1_Channel7, DMA_IT_TC, ENABLE);

     // NVIC for DMA

     NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel7_IRQn;

     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

     NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

     NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

     NVIC_Init(&NVIC_InitStructure);

}

void vStartDMA(uint8_t *PtrDataToSend, uint16_t LengthOfData) {

     /* DMA Channel7 Configuration ----------------------------------------------*/

     DMA_InitTypeDef DMAInitStructure;

     if (!DMA_BUSY) {

          DMA_BUSY = TRUE;

          DMAInitStructure.DMA_DIR                               = DMA_DIR_PeripheralDST, 

          DMAInitStructure.DMA_BufferSize                    = LengthOfData,

          DMAInitStructure.DMA_MemoryBaseAddr               = (uint32_t) PtrDataToSend,

          DMAInitStructure.DMA_MemoryDataSize           = DMA_MemoryDataSize_Byte, 

          DMAInitStructure.DMA_MemoryInc                     = DMA_MemoryInc_Enable,

          DMAInitStructure.DMA_Mode                               = DMA_Mode_Normal,

          DMAInitStructure.DMA_PeripheralBaseAddr     = (uint32_t) & TIM2->CCR4,

          DMAInitStructure.DMA_PeripheralDataSize      = DMA_PeripheralDataSize_Byte,

          DMAInitStructure.DMA_PeripheralInc                = DMA_PeripheralInc_Disable,

          DMAInitStructure.DMA_Priority                     = DMA_Priority_VeryHigh,

          DMAInitStructure.DMA_M2M                               = DMA_M2M_Disable;

          DMA_Cmd(DMA1_Channel7, DISABLE);

          DMA_Init(DMA1_Channel7, &DMAInitStructure);

          DMA_Cmd(DMA1_Channel7, ENABLE);

          TIM_DMACmd(TIM2, TIM_DMA_CC4, ENABLE);

     }

}

void DMA1_Channel7_IRQHandler()

  {

       disableInterrupts();

    //NoInterrupts lock;

    DMA_ClearITPendingBit(DMA1_IT_TC7);

    DMA_Cmd(DMA1_Channel7, DISABLE);

    DMA_BUSY = FALSE;

       enableInterrupts();

  }