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

本文引用地址: http://www.21ic.com/app/mcu/201806/764278.htm

#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