STM32 双DAC DMA TIM6输出正弦波例子

STM32F103有双DAC通道，利用DMA实现2个波形输出

#include "stm32f10x.h"

//DAC1,2初始化
void dac_init(void)
{
    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN; //开启端口A时钟
    RCC->APB1ENR |= RCC_APB1ENR_DACEN; //开启DAC时钟
    
    GPIOA->CRL &= 0xff00ffff; //PA4,PA5模拟输入
    
    DAC->CR = DAC_CR_TEN1 | DAC_CR_TEN2; //开启触发使能才能设置触发模式
    //开启DAC,关闭输出缓存,TIM6 TRGO触发,DMA使能
    DAC->CR |= DAC_CR_EN1 | DAC_CR_BOFF1 | DAC_CR_DMAEN1 | \
               DAC_CR_EN2 | DAC_CR_BOFF2 | DAC_CR_DMAEN2;
    //必须关闭缓冲才能输出低于0.5V电压
}

//DMA2初始化
void dma2_init(unsigned int cpar, unsigned int cmar, unsigned int cndtr)
{
    RCC->AHBENR |= RCC_AHBENR_DMA2EN; //开启DMA2时钟

    DMA2_Channel3->CPAR = cpar; //外设地址
    DMA2_Channel3->CMAR = cmar; //存储器地址
    DMA2_Channel3->CNDTR = cndtr; //传输数据量
    
    //通道开启,从存储器读,循环,外设不自增,存储器自增
    //外设32位数据,存储器32位数据,优先级最高,非存储器到存储器
    DMA2_Channel3->CCR = DMA_CCR3_EN | DMA_CCR3_DIR | DMA_CCR3_CIRC | \
                         DMA_CCR3_MINC | DMA_CCR3_PSIZE_1 | DMA_CCR3_MSIZE_1 | \
                         DMA_CCR3_PL_0 | DMA_CCR3_PL_1;
}

//TIM6初始化
void tim6_init(unsigned short arr, unsigned short psc)
{
    RCC->APB1ENR |= RCC_APB1ENR_TIM6EN; //开启TIM6时钟
    
    TIM6->PSC = psc; //预分频器
    TIM6->ARR = arr; //自动重装载

    TIM6->CR2 &= 0xff8f;
    TIM6->CR2 |= TIM_CR2_MMS_1; //更新事件用作TRGO
    
    TIM6->CR1 &= 0xff70;
    TIM6->CR1 |= TIM_CR1_CEN | TIM_CR1_ARPE; //使能计数器,非单脉冲模式,自动重装载
}

初始化RCC时钟为72MHz，正弦波1000点，2个波形，一个反相，一个幅度改变

    for(i = 0; i < 1000; i++)
    {
        sw[i] = 4095 - sine_wave[i];
        sw[i] <<= 16;
        sw[i] += sine_wave[i] / 3;
    }
    
    dma2_init((unsigned int)&DAC->DHR12RD, (unsigned int)sw, 1000);
    dac_init();
    tim6_init(7200, 0);

ARR为7199，PSC为0，72M/7199/1000=10Hz波形频率，修改预分频和重装载数值可以改变波形频率

计算公式：f=fosc/n/(arr+1)/(psc+1)

f-波形频率

n-波形点数

arr-定时器计数，不能为0

psc-时钟分频系数

fosc-系统时钟，一般PLL后为72MHz