STM32F4 DAC Problem

GPIO_InitTypeDef GPIO_InitStruct;

DAC_InitTypeDef DAC_InitStruct;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

...

//Weitere Inits

...

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_4;

GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;

GPIO_Init(GPIOA, &GPIO_InitStruct);

DAC_InitStruct.DAC_Trigger = DAC_Trigger_None;

DAC_InitStruct.DAC_WaveGeneration = DAC_WaveGeneration_None;

DAC_InitStruct.DAC_OutputBuffer = DAC_OutputBuffer_Enable;

DAC_Init(DAC_Channel_1, &DAC_InitStruct);

DAC_Cmd(DAC_Channel_1, ENABLE);

DAC_SetChannel1Data(DAC_Align_12b_R, 2048);