DAC problem with STM32F4

[ennioaloisini]

Posted on March 17, 2014 at 18:51

Dear All,

I have tested the DAC example on the STM32F429 and I have understood the way using / driving the DAC on the STM32F4. I have tried to create my sample code using the STM32F429 Discovery template, but nothing happened.

Here below the code:

RCC_AHB1PeriphClockCmd (RCC_AHB1Periph_GPIOA, ENABLE);

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);

  

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE);

TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);

TIM_TimeBaseStructure.TIM_Period = 0xFF;

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_ClockDivision = 0;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 

TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure);

TIM_SelectOutputTrigger(TIM6, TIM_TRGOSource_Update);

TIM_Cmd(TIM6, ENABLE);

  

DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;

DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;

DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;

DAC_Init(DAC_Channel_1, &DAC_InitStructure);

DAC_Cmd(DAC_Channel_1, ENABLE);

DAC_SetChannel1Data(DAC_Align_12b_R, 500);

I Have checked with the oscilloscope, but nothing changes.

Then I have tested the DAC_SignalGeneration and it run correctly.

Then I have tried to modify the DAC_SignalGeneration example and I have only changed this piece of code:

while (1)

  {

    /* If the User Button is pressed */

    if (KeyPressed == RESET)

    {            

      DAC_DeInit(); 

      /* select waves forms according to the Key Button status */

      if (SelectedWavesForm == 1)

      {

        /* The sine wave and the escalator wave has been selected */

        /* Escalator Wave generator ------------------------------------------*/

        DAC_Ch1_EscalatorConfig();

        /* Sine Wave generator -----------------------------------------------*/

        DAC_Ch2_SineWaveConfig();

         

      }

      else

      {

        /* The triangle wave and the noise wave has been selected */

        /* Noise Wave generator ----------------------------------------------*/

        DAC_Ch1_NoiseConfig();

        /* Triangle Wave generator -------------------------------------------*/

        DAC_Ch2_TriangleConfig();

      }

      

      KeyPressed = SET; 

    }

  }

 In the following way:

while (1)

  {

    /* If the User Button is pressed */

    if (KeyPressed == RESET)

    {            

      DAC_DeInit(); 

      /* select waves forms according to the Key Button status */

      if (SelectedWavesForm == 1)

      {

        /* The sine wave and the escalator wave has been selected */

        /* Escalator Wave generator ------------------------------------------*/

        //DAC_Ch1_EscalatorConfig();

        /* Sine Wave generator -----------------------------------------------*/

        DAC_Ch2_SineWaveConfig();

         

      }

      else

      {

        /* The triangle wave and the noise wave has been selected */

        /* Noise Wave generator ----------------------------------------------*/

        //DAC_Ch1_NoiseConfig();

        /* Triangle Wave generator -------------------------------------------*/

        //DAC_Ch2_TriangleConfig();

      }

      

      KeyPressed = SET; 

    }

  }

Sincerly I do not understand where is the problem, I have read a lot of things on internet and I have tried to do all the possible changes, but the DAC does not run with and without DMA.

Could someone help me about this problem?

Thanks!

[chen]

Posted on March 18, 2014 at 10:23

Hi

A quick glance through your code :

''GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;''

I think this should be : GPIO_Mode_AF

for alternate function mode.

Also, there should be some code to select the Alternate Function for thise pins.

[ennioaloisini]

Posted on March 18, 2014 at 12:53

Hello,

thank you very much for the answer.

I have checked many examples and they configure the pin AN (Analog) not AF.

In the STM32F4XX PINA4 is the DAC 1 and PINA5 is the DAC 2.

Let me know!

Best regards

[frankmeyer9]

Posted on March 18, 2014 at 13:27

In the STM32F4XX PINA4 is the DAC 1 and PINA5 is the DAC 2.

 

Are you sure ?

Better check the datasheet of your F4xx derivate.

And when about it, check that nothing else is connected to the DAC out pins.

The DAC has a rather high output impedance even in buffered mode, and is easily overdriven by other peripherals attached to the line.

[Tesla DeLorean]

Posted on March 18, 2014 at 14:40

Definitely want to check the STM32F429I-DISCO schematic/manual, only PA5 is free on the board.

For the STM32F4-DISCO I had an [DEAD LINK /public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Help%20with%20simple%20ADC%20on%20STM32F4&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=593]example about 80% down this thread.

[ennioaloisini]

Posted on March 19, 2014 at 18:55

Thank you very much for the support!

Now it works fine on the EVAL board.

Best regards

[mikemillernow]

Posted on March 19, 2014 at 20:06

Aloisini.,

What did you change to get this to work?  I am facing a similar issue and would like to know the details.

Thanks.

-Mike.