STM32-Peripheral’s-DAC:

The Digital to Analog converter (DAC) is a device, that is widely used for converting digital pulses to analog signals. There are two methods of converting digital signals to analog signals. These two methods are binary weighted method and R/2R ladder method. DACs are judged by its resolution. The resolution is a function of the number of binary inputs. The most common input counts are 8, 10, 12 etc. Number of data inputs decides the resolution of DAC. So if there are n digital input pin, there are 2ⁿ analog levels. So 8 input DAC has 256 discrete voltage levels.

The applications of Digital to Analog Converter include:

• DAC’s are used in Digital Signal Processing.
• They are also used in digital power supplies for Micro-controller.
• DAC’s are used in digital potentiometers.
• They are used in all digital data acquisition systems.
• Used to tune RF Component’s such as TCXO

DAC Channels (STM32F429xx)
The device integrates two 12-bit Digital Analog Converters that can be used independently or simultaneously
(dual mode):
1. DAC channel1 with DAC_OUT1 (PA4) as output
2. DAC channel2 with DAC_OUT2 (PA5) as output

DAC data format
The DAC data format can be:
1. 8-bit right alignment using DAC_ALIGN_8B_R
2. 12-bit left alignment using DAC_ALIGN_12B_L
3. 12-bit right alignment using DAC_ALIGN_12B_R

DAC data value to voltage correspondence
The analog output voltage on each DAC channel pin is determined by the following equation: DAC_OUTx = VREF
+ * DOR / 4095 with DOR is the Data Output Register VEF+ is the input voltage reference (refer to the device
datasheet) e.g. To set DAC_OUT1 to 0.7V, use Assuming that VREF+ = 3.3V, DAC_OUT1 = (3.3 * 868) / 4095 =
0.7V

For this blog we are going to use ADC in polling mode without averaging to demonstrate DAC functionality

Creating STM32 executable projects steps are available on this link , please follow steps 1 to 10 as per blog, here we will start from step 11. PA9 & PA10 Pin used for debugging purpose as UART Tx & UART Rx respectively.

11. Enable DAC Functionality

Go to System mode > Analog > DAC > Enable Out1 Configuration > keep all other settings as its

12. Enable ADC Functionality

Go to System mode > Analog > ADC > Enable IN0 > keep all other settings as its

13. Press below icon for code generation

14.For code demonstration we will connect DAC Output to ADC Input , already we have configured UART1 for debugging purpose.

15. Sample Code

  /* USER CODE BEGIN 2 */
  HAL_DAC_Start(&hdac, DAC_CHANNEL_1);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */

	  HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, dac_data);
	  HAL_Delay(500);	//2000 ms delay
	  HAL_ADC_Start(&hadc3);

	   if(HAL_ADC_PollForConversion(&hadc3, 50) == HAL_OK)
	   {
	 	  adcvalue = HAL_ADC_GetValue(&hadc3);
	   }
  }
  /* USER CODE END 3 */
}

Software Tools:

1. STM32CubeIDE
2. STM32CubeMx
3. Teraterm

Hardware Setup;

1. STM32F429IDISCOVERY board
2. Mini USB Cable
3. Jumper wire

Conclusion:

Successfully demonstrated DAC functionality with default configuration, for testing purpose we have used ADC in polling mode

References:

1. STM32 HAL Library
2. STM32 UM1718 document

Similar topics:

1. https://kalapiinfotech.in/stm32-cube-ide-freertos-code-generation-using-cubemx/
2. https://kalapiinfotech.in/stm32-peripherals-gpio-output-input/