How to calibrate the DACs on STM32 using the HAL library ?

Posted on February 08, 2017 at 19:25

Hello,

I am using the the HAL library for calibrating the DAC on STM32L4.

I read the documentation for  DAC on page 286 (DOCID027704 Rev 4) in HAL L4 user manual. I am still confused about how to correctly use the HAL DAC calibration APIs.

My question is how does the 

HAL_DACEx_SelfCalibrate() API work? Does it automatically apply the trimming offset? 

or do I also need to use the APIs below?

HAL_DACEx_GetTrimOffset()

HAL_DACEx_SetUserTrimming()

If yes should I be manually adding the TrimOffset before making a call to 

HAL_DAC_SetValue, s

omething like below?

trim_offset = HAL_DACEx_GetTrimOffset(&hdac1, DAC_CHANNEL_2)

HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_2, DAC_ALIGN_8B_R, input_data + trim_offset )?

Just for reference I have posted my current code below.

Below is my current calibration function:

void DAC_SelfCalibrate(void)

{

   DAC_ChannelConfTypeDef sConfig;

   sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;

   sConfig.DAC_Trigger = DAC_TRIGGER_NONE;

   sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;

   sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE;

   sConfig.DAC_UserTrimming = DAC_TRIMMING_USER;

   //Calibrate DAC channel 1

   if (HAL_DACEx_SelfCalibrate(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)

   {

      Error_Handler();

   }

   //Calibrate DAC channel 2

   sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE;

   if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_2) != HAL_OK)

   {

      Error_Handler();

   }

}

and here is my  code to set the DAC

int set_dac_val(uint8_t input_index, uint8_t input_data)

{

   //set dac channel 1

   if(input_index==0) {

      HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_8B_R, input_data);

   //set dac channel 2

   }

   else if(input_index==1)

   {

      HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_2, DAC_ALIGN_8B_R, input_data);

   }

   return 0;

}

Below is my sequence of calls for initialization.

MX_DAC1_Init(); 

DAC_SelfCalibrate();

HAL_DAC_Start(&hdac1, DAC_CHANNEL_1);

HAL_DAC_Start(&hdac1, DAC_CHANNEL_2);

I have a similar question about HAL based ADC calibration and usage of calibration factor. I will post that under a separate thread.

Thanks!

#hal #dac #calibration