DAC programme - no desired output signal (too much noise)

[KRISH_]

I am using NUCLEO-H7A3ZI-Q (32 bits) . While Debugging the LED4 starts blinking solid red and never exits debugging,it shows a breaking point at MCU config();.

I was running a program to obtain a sawtooth wave through the DAC pin PA5.

/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2025 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
COM_InitTypeDef BspCOMInit;
DAC_HandleTypeDef hdac1;
/* USER CODE BEGIN PV */
uint32_t dac_value=0;
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MPU_Config(void);
static void MX_GPIO_Init(void);
static void MX_DAC1_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**

* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MPU Configuration--------------------------------------------------------*/
MPU_Config();
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
printf("SystemCoreClock: %lu\n", SystemCoreClock);
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_DAC1_Init();
/* USER CODE BEGIN 2 */
HAL_DAC_Start(&hdac1, DAC_CHANNEL_2);
/* USER CODE END 2 */
/* Initialize leds */
BSP_LED_Init(LED_GREEN);
BSP_LED_Init(LED_YELLOW);
BSP_LED_Init(LED_RED);
/* Initialize USER push-button, will be used to trigger an interrupt each time it's pressed.*/
BSP_PB_Init(BUTTON_USER, BUTTON_MODE_EXTI);
/* Initialize COM1 port (115200, 8 bits (7-bit data + 1 stop bit), no parity */
BspCOMInit.BaudRate = 115200;
BspCOMInit.WordLength = COM_WORDLENGTH_8B;
BspCOMInit.StopBits = COM_STOPBITS_1;
BspCOMInit.Parity = COM_PARITY_NONE;
BspCOMInit.HwFlowCtl = COM_HWCONTROL_NONE;
if (BSP_COM_Init(COM1, &BspCOMInit) != BSP_ERROR_NONE)
{
Error_Handler();
}
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_2, DAC_ALIGN_12B_R, dac_value);
if (dac_value < 4095) {
dac_value++;
} else {

dac_value=0;
}
HAL_Delay(1);
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/*AXI clock gating */
RCC->CKGAENR = 0xFFFFFFFF;
/** Supply configuration update enable
*/
HAL_PWREx_ConfigSupply(PWR_DIRECT_SMPS_SUPPLY);
/** Configure the main internal regulator output voltage
*/
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);
while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSI;
RCC_OscInitStruct.HSIState = RCC_HSI_DIV1;
RCC_OscInitStruct.HSICalibrationValue = 64;
RCC_OscInitStruct.LSIState = RCC_LSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 4;
RCC_OscInitStruct.PLL.PLLN = 8;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
|RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV1;
RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief DAC1 Initialization Function
* @PAram None
* @retval None
*/
static void MX_DAC1_Init(void)
{
/* USER CODE BEGIN DAC1_Init 0 */
/* USER CODE END DAC1_Init 0 */
DAC_ChannelConfTypeDef sConfig = {0};
/* USER CODE BEGIN DAC1_Init 1 */
/* USER CODE END DAC1_Init 1 */
/** DAC Initialization
*/
hdac1.Instance = DAC1;
if (HAL_DAC_Init(&hdac1) != HAL_OK)
{
Error_Handler();
}
/** DAC channel OUT2 config
*/
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_FACTORY;
if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN DAC1_Init 2 */
/* USER CODE END DAC1_Init 2 */
}
/**
* @brief GPIO Initialization Function

* @PAram None
* @retval None
*/
static void MX_GPIO_Init(void)
{
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOH_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/* MPU Configuration */
void MPU_Config(void)
{
MPU_Region_InitTypeDef MPU_InitStruct = {0};
/* Disables the MPU */
HAL_MPU_Disable();
/** Initializes and configures the Region and the memory to be protected
*/
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.Number = MPU_REGION_NUMBER0;
MPU_InitStruct.BaseAddress = 0x0;
MPU_InitStruct.Size = MPU_REGION_SIZE_4GB;
MPU_InitStruct.SubRegionDisable = 0x87;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);
/* Enables the MPU */
HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);
}
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)

{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @PAram file: pointer to the source file name
* @PAram line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

https://wiki.st.com/stm32mcu/wiki/Getting_started_with_DAC

[Edited for the code: next time use the </> icon to insert code JW]

[waclawek.jan]

> no desired output signal (too much noise)

Show.

Also, what equipment do you use and how exactly do you connect ground?

JW

[KRISH_]

thankyou for the reply .frequency coming in kHZ and MHZ

[KRISH_]

[KRISH_]

in CN7 pin no.8 for GND and pin no.10 for DAC (PA5)

[waclawek.jan]

Something is very wrong.

Try to connect the ground clip to the pins in the corners.

Try to connect the probe to GND, still noise?

Do you see this noise also when the processor is held in reset (simply by holding down the reset button)?

And what happens if you set one single voltage level in the DAC (say, 1/3 full scale) and then do nothing in the main loop?

Btw. you have set the oscilloscope to 10x probe but have the probe switched to 1x, so the numbers are off by factor of 10, but still the amplitude of that noise is baffling. There's also seldom any reason to use AC coupling when measuring on mcu pins.

JW

[MasterT]

I see, that writing 

HAL_DAC_SetValue(&amp;hdac1, DAC_CHANNEL_2, DAC_ALIGN_12B_R, dac_value);

running in the while{} loop, so the timing is not determined in any way. Likely DAC is overclocked, max conversion about 1 msps, same time cycles likely runs much faster. Second issue with this approach is that "gaps" happened whenever uCPU interrupted by .. an interrupt   :);

Use timer to trigger conversion, there are a lot of examples of code in CubeMX, almost any uCPU includes such code

[waclawek.jan]

I see HAL_Delay(1); in that loop, but maybe I'm misunderstanding something, as I don't Cube.

JW

[MasterT]

Right, than next question why delay() doesn't work? If I correctly understand, oscilloscope running at 5usec /div.

Second line in google search on HAL_Delay() brings

https://community.st.com/t5/stm32-mcus-products/hal-delay/td-p/62617

I didn't use HAL_Delay() before, seems like it needs systick be activated

[waclawek.jan]

I don't think it's HAL_Delay() which does not work here.

JW