STM32F103有雙DAC通道，利用DMA實現(xiàn)2個波形輸出

#include "stm32f10x.h"  

//DAC1,2初始化  

void dac_init(void)  

{  

    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN; //開啟端口A時鐘  

    RCC->APB1ENR |= RCC_APB1ENR_DACEN; //開啟DAC時鐘  

    GPIOA->CRL &= 0xff00ffff; //PA4,PA5模擬輸入  

    DAC->CR = DAC_CR_TEN1 | DAC_CR_TEN2; //開啟觸發(fā)使能才能設置觸發(fā)模式  

    //開啟DAC,關閉輸出緩存,TIM6 TRGO觸發(fā),DMA使能  

    DAC->CR |= DAC_CR_EN1 | DAC_CR_BOFF1 | DAC_CR_DMAEN1 | \  

               DAC_CR_EN2 | DAC_CR_BOFF2 | DAC_CR_DMAEN2;  

    //必須關閉緩沖才能輸出低于0.5V電壓  

}  

//DMA2初始化  

void dma2_init(unsigned int cpar, unsigned int cmar, unsigned int cndtr)  

{  

    RCC->AHBENR |= RCC_AHBENR_DMA2EN; //開啟DMA2時鐘  

    DMA2_Channel3->CPAR = cpar; //外設地址  

    DMA2_Channel3->CMAR = cmar; //存儲器地址  

    DMA2_Channel3->CNDTR = cndtr; //傳輸數(shù)據(jù)量  

    //通道開啟,從存儲器讀,循環(huán),外設不自增,存儲器自增  

    //外設32位數(shù)據(jù),存儲器32位數(shù)據(jù),優(yōu)先級最高,非存儲器到存儲器  

    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; //開啟TIM6時鐘  

    TIM6->PSC = psc; //預分頻器  

    TIM6->ARR = arr; //自動重裝載  

    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; //使能計數(shù)器,非單脈沖模式,自動重裝載  

}  

初始化RCC時鐘為72MHz，正弦波1000點，2個波形，一個反相，一個幅度改變

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為7199，PSC為0，72M/7199/1000=10Hz波形頻率，修改預分頻和重裝載數(shù)值可以改變波形頻率

計算公式：f=fosc/n/(arr+1)/(psc+1)

f-波形頻率

n-波形點數(shù)

arr-定時器計數(shù)，不能為0

psc-時鐘分頻系數(shù)

fosc-系統(tǒng)時鐘，一般PLL后為72MHz