stm32基本定时器触发dac

首先需要初始化定时器和DAC模块，然后在定时器的中断函数中将DAC输出值更新为预设值。

下面是一个基本的示例代码：

#include "stm32f10x.h"

void TIM2_IRQHandler(void)
{
    if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        // 更新DAC输出值为预设值
        DAC_SetChannel1Data(DAC_Align_12b_R, 2048);

        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
    }
}

int main(void)
{
    // 初始化定时器
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
    TIM_TimeBaseInitStruct.TIM_Period = 35999;
    TIM_TimeBaseInitStruct.TIM_Prescaler = 0;
    TIM_TimeBaseInitStruct.TIM_ClockDivision = 0;
    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStruct.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStruct);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

    NVIC_InitTypeDef NVIC_InitStruct;
    NVIC_InitStruct.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);

    // 初始化DAC
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

    DAC_InitTypeDef DAC_InitStruct;
    DAC_InitStruct.DAC_Trigger = DAC_Trigger_T2_TRGO;
    DAC_InitStruct.DAC_WaveGeneration = DAC_WaveGeneration_None;
    DAC_InitStruct.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
    DAC_Init(DAC_Channel_1, &DAC_InitStruct);

    // 启动定时器
    TIM_Cmd(TIM2, ENABLE);

    while (1)
    {
        // do something
    }
}

在本示例中，定时器TIM2的周期设置为36000（即每秒触发一次中断），并且启用了中断功能。在中断处理函数中，更新DAC的输出值为预设值2048，这个值可以根据实际需求进行修改。

同时，在DAC初始化时，将其触发源设置为定时器2的触发输出TRGO，这样每次定时器触发时，DAC会输出相应的电压值。