Nucleof446re DAC

[harry123]

Hi 

• I am trying to generate a Dc volatge ramp signal 0 to 1v and 1v to 0 
• I want to stop the signal on pressing the user button pc13.
• I am able stop the dac but the output on pin PA4 with respect to gnd  is 0.02V 

#include "stm32f4xx_hal.h"

// Define DAC handle and resolution
DAC_HandleTypeDef hdac;
#define DAC_RESOLUTION 1241   
// Button press flag
volatile uint8_t button_pressed = 0;

// Function to initialize DAC
void DAC_Init(void)
{
    __HAL_RCC_DAC_CLK_ENABLE();  // Enable DAC clock

    hdac.Instance = DAC;
    HAL_DAC_Init(&hdac);  // Initialize DAC

    DAC_ChannelConfTypeDef sConfig = {0};
    sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
    sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_DISABLE;  // Disable output buffer
    HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_1);
    HAL_DAC_Start(&hdac, DAC_CHANNEL_1);  // Start DAC
}

// Function to initialize button (PC13)
void Button_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStruct = {0};
    __HAL_RCC_GPIOC_CLK_ENABLE();

    GPIO_InitStruct.Pin = GPIO_PIN_13;
    GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;  // Falling edge trigger (button press)
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

    // Enable EXTI interrupt for line 13 (PC13)
    HAL_NVIC_SetPriority(EXTI15_10_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(EXTI15_10_IRQn);
}

// Interrupt handler for button press (PC13)
void EXTI15_10_IRQHandler(void)
{
    static uint32_t last_interrupt_time = 0;
    uint32_t interrupt_time = HAL_GetTick();

    if (__HAL_GPIO_EXTI_GET_IT(GPIO_PIN_13) != RESET)
    {
        // Clear the interrupt flag
        __HAL_GPIO_EXTI_CLEAR_IT(GPIO_PIN_13);

        // Simple debounce check: ignore if the interrupt happens too quickly after the last one
        if (interrupt_time - last_interrupt_time > 50)  // 50 ms debounce
        {
            last_interrupt_time = interrupt_time;

            // Set flag to indicate button press
            button_pressed = 1;
        }
    }
}

// Ramp DAC function (0 to 1V and back)
void Ramp_DAC(void)
{
    uint32_t dacValue;
    int32_t direction = 1; // Ramp direction: 1 = up, -1 = down

    while (1)
    {
        // Polling button press status in main loop
        if (button_pressed)
        {
            // Set DAC to 0V (explicitly force DAC to 0)
            HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, 0);
            
            // Stop the DAC output to force it to 0V
            HAL_DAC_Stop(&hdac, DAC_CHANNEL_1);
            break;  // Stop the ramp
        }

        // Ramp the DAC value
        if (direction == 1)
        {
            for (dacValue = 0; dacValue < DAC_RESOLUTION; dacValue++)
            {
                HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, dacValue);
                HAL_Delay(1);  // Adjust ramp speed
            }
            direction = -1;  // Change direction to ramp down
        }
        else
        {
            for (dacValue = DAC_RESOLUTION; dacValue > 0; dacValue--)
            {
                HAL_DAC_SetValue(&hdac, DAC_CHANNEL_1, DAC_ALIGN_12B_R, dacValue);
                HAL_Delay(1);  // Adjust ramp speed
            }
            direction = 1;  // Change direction to ramp up
        }
    }
}

int main(void)
{
    HAL_Init();
    DAC_Init();
    Button_Init();
    Ramp_DAC();

    while (1)
    {
        
    }
}​

• whereas i can measure 0.001v smallest volatge 
• I want the value 0 or close to zero on pressing user button I have attached the code below

Thank you.