Noisy DAC on STM32F303

[epalaima]

Posted on August 08, 2016 at 22:39

Hi, I just set up DAC output on the STM32F303 Discovery Board and I'm noticing a lot of wideband noise on the output (about .5 volts peak to peak), even when I set it to a constant value within my program. Is there something in the way I'm am setting up DAC output that might be causing this? I based the output configuration off of the DMA_RAM_DAC peripheral example project.

Here is my code for setting up DAC output, please let me know if you see anything: int main(void){  /*!< At this stage the microcontroller clock setting is already configured,        this is done through SystemInit() function which is called from startup       file (startup_stm32f30x.s) before to branch to application main.       To reconfigure the default setting of SystemInit() function, refer to       system_stm32f30x.c file     */    DMA_Config();  DAC_Config();  TIM_Config();  while (1)  {  DAC1Output = 4095;  }}/**  * @brief  Configures the TIM2  * @param  None  * @retval None  */static void TIM_Config(void){  TIM_TimeBaseInitTypeDef    TIM_TimeBaseStructure;  /* TIM2 Periph clock enable */  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);  /* Time base configuration */  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);   TIM_TimeBaseStructure.TIM_Period = 0xFF;//0xFF;  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;         TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;      TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);  /* TIM2 TRGO selection: update event is selected as trigger for DAC */  TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);  /* TIM2 enable counter */  TIM_Cmd(TIM2, ENABLE);}/**  * @brief  Configures DAC channel 1 and channel 2  * @param  None  * @retval None  */static void DAC_Config(void){  DAC_InitTypeDef   DAC_InitStructure;  GPIO_InitTypeDef  GPIO_InitStructure;    /* Enable GPIOA Periph clock --------------------------------------*/  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);    /* Configure PA.04 (DAC1_OUT1), PA.05 (DAC1_OUT2) as analog */  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_4 | GPIO_Pin_5;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;  GPIO_Init(GPIOA, &GPIO_InitStructure);    /* DAC Periph clock enable */  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);    /* Fill DAC InitStructure */  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T2_TRGO;  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;  //DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_4095;  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;    /* DAC channel1 Configuration */  DAC_Init(DAC_Channel_1, &DAC_InitStructure);    /* DAC channel2 Configuration */  DAC_Init(DAC_Channel_2, &DAC_InitStructure);    /* Enable DAC Channel1: Once the DAC channel1 is enabled, PA.04 is   automatically connected to the DAC converter. */  DAC_Cmd(DAC_Channel_1, ENABLE);    /* Enable DAC Channel2: Once the DAC channel2 is enabled, PA.05 is   automatically connected to the DAC converter. */  DAC_Cmd(DAC_Channel_2, ENABLE);    /* Enable DMA for DAC Channel1 */  DAC_DMACmd(DAC_Channel_1, ENABLE);}/**  * @brief  Configures DMA2 channel3  * @param  None  * @retval None  */static void DMA_Config(void){  DMA_InitTypeDef   DMA_InitStructure;  /* Enable DMA2 clock -------------------------------------------------------*/  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2, ENABLE);  DMA_DeInit(DMA2_Channel3);  DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12RD_Address;  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&DAC1Output;  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;  DMA_InitStructure.DMA_BufferSize = 1;  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;  DMA_InitStructure.DMA_Priority = DMA_Priority_High;  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;  DMA_Init(DMA2_Channel3, &DMA_InitStructure);  /* Enable DMA2 Channel3 */  DMA_Cmd(DMA2_Channel3, ENABLE);} #stm32 #dac #noise #stm32f303

[Walid FTITI_O]

Posted on August 16, 2016 at 18:05

Hi , 

Be careful to these points :+ Check if the 

PeripheralBaseAddr ''DAC_DHR12RD_Address;'' is correct . T think the corret one is ''DAC_DHR12R2_Address;''

+ Check the wave generation parameters which is set to none . I think it should be chaged to  ''DAC_WaveGeneration_Triangle''-Hannibal-