DAC output not working

danieloneill9 · ‎2012-09-04

Posted on September 05, 2012 at 04:38

Hi All,

I had the DAC working using DMA to out put a sinewave continuously and it seems to have stopped working when I tried to change which timer I triggered off. After changing the timer configuration back it still doesn't work.

I believe I configure everything I need to and I have code that read DAC->DOR1 out via the USART and it shows this data updating as I expect but I don't see any voltage on the DAC pin.

Any ideas?

Regards,

Daniel

#dac

Tesla DeLorean · ‎2012-09-04

Posted on September 05, 2012 at 05:13

Sounds like a pin configuration or VDDA issue.

What part are we talking about?

What does the pin config code look like?

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danieloneill9 · ‎2012-09-05

Posted on September 06, 2012 at 08:05

Hi Clive,

The part is a STM32F103.

The pin config code is as follows:

GPIO_InitTypeDef GPIO_InitStructure = {

GPIO_Pin_4,

GPIO_Speed_50MHz,

GPIO_Mode_AIN

};

GPIO_Init(GPIOA, &GPIO_InitStructure);

Cheers,

Daniel

szbrozek9 · ‎2012-09-05

Posted on September 06, 2012 at 08:53

I noticed that you didn't use the GPIO configuration system in the canonical way, but checking the GPIO_InitStruct suggests that what you did should work. Quick overall DAC checklist:

Did you turn on the DAC and GPIO clocks before configuring the peripherals:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

Did you configure the DAC:

DAC_InitStructure.DAC_Trigger = DAC_Trigger_Software;

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);

Did you actually write something to the DAC:

DAC_SetChannel1Data(DAC_Align_12b_R, 0x07FF);

DAC_SoftwareTriggerCmd(DAC_Channel_1, ENABLE);

danieloneill9 · ‎2012-09-06

Posted on September 06, 2012 at 09:31

clocks

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

DAC

DAC_InitTypeDef DAC_InitStructure = {

DAC_Trigger_T4_TRGO, /*DAC_Trigger*/

DAC_WaveGeneration_None, /*DAC_WaveGeneration*/

DAC_LFSRUnmask_Bit0, /*DAC_LFSRUnmask_TriangleAmplitude*/

DAC_OutputBuffer_Disable /*DAC_OutputBuffer*/

};

I have a DMA loop that writes to the DAC. When I poll the DAC->DOR1 register I see data in there changing as I expect.

szbrozek9 · ‎2012-09-06

Posted on September 06, 2012 at 09:44

szbrozek9 · ‎2012-09-06

Posted on September 06, 2012 at 09:45

szbrozek9 · ‎2012-09-06

Posted on September 06, 2012 at 09:46

danieloneill9 · ‎2012-09-06

Posted on September 06, 2012 at 12:21

Hi All,

A poke round and a clean build later and the DAC is working.....

Thanks for the help.

Cheers,

Daniel

megapin · ‎2013-01-29

Posted on January 29, 2013 at 19:53

Hi!

board: STM32VL Discovery

DAC1,DAC2 DORx Register = 0;

Why out voltage = 60 mV?