STM32F1自带的DAC模块的使用。但有时候，可能两个DAC不够用，我们可以通过PWM+RC滤波来实现一个PWM DAC。本章将向大家介绍如何利用STM32的PWM来设计一个DAC。利用按键（USMART）控制STM32的PWM输出，从而控制PWM DAC的输出电压，通过ADC1的通道1采集PWM DAC的输出电压，并在LCD模块上面显示ADC获取到的电压值以及PWM DAC的设定输出电压值等信息。
main函数
- #include "led.h"
- #include "delay.h"
- #include "key.h"
- #include "sys.h"
- #include "lcd.h"
- #include "usart.h"
- #include "rtc.h"
- #include "wkup.h"
- #include "adc.h"
- #include "dac.h"
- #include "timer.h"
- #include "usmart.h"
- //设置输出电压
- //vol:0~330,代表0~3.3V
- void PWM_DAC_Set(u16 vol)
- {
- float temp=vol;
- temp/=100;
- temp=temp*256/3.3;
- TIM_SetCompare1(TIM1,temp);
- }
- int main(void)
- {
- u16 adcx;
- float temp;
- u8 t=0;
- u16 pwmval=0;
- u8 key;
-
- delay_init(); //延时函数初始化
- NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
- uart_init(115200); //串口初始化为115200
- KEY_Init(); //KEY初始化
- LED_Init(); //LED端口初始化
- usmart_dev.init(72); //初始化USMART
- LCD_Init(); //LCD初始化
- Adc_Init(); //ADC初始化
-
- TIM1_PWM_Init(255,0); //TIM1 PWM初始化,计数周期为256，Fpwm=72M/256=281.25Khz.
- TIM_SetCompare1(TIM1,100);//初始值为0
-
- POINT_COLOR=RED;//设置字体为红色
- LCD_ShowString(60,50,200,16,16,"WarShip STM32");
- LCD_ShowString(60,70,200,16,16,"PWM DAC TEST");
- LCD_ShowString(60,90,200,16,16,"ATOM@ALIENTEK");
- LCD_ShowString(60,110,200,16,16,"2015/1/15");
- LCD_ShowString(60,130,200,16,16,"WK_UP:+ KEY1:-");
- //显示提示信息
- POINT_COLOR=BLUE;//设置字体为蓝色
- LCD_ShowString(60,150,200,16,16,"PWM VAL:");
- LCD_ShowString(60,170,200,16,16,"DAC VOL:0.000V");
- LCD_ShowString(60,190,200,16,16,"ADC VOL:0.000V");
-
- TIM_SetCompare1(TIM1,pwmval);//初始值
- while(1)
- {
- t++;
- key=KEY_Scan(0);
- if(key==WKUP_PRES)
- {
- if(pwmval<250)pwmval+=10;
- TIM_SetCompare1(TIM1,pwmval); //输出
- }else if(key==KEY1_PRES)
- {
- if(pwmval>10)pwmval-=10;
- else pwmval=0;
- TIM_SetCompare1(TIM1,pwmval); //输出
- }
-
- if(t==10||key==KEY1_PRES||key==WKUP_PRES) //WKUP/KEY1按下了,或者定时时间到了
- {
- adcx=TIM_GetCapture1(TIM1);
- LCD_ShowxNum(124,150,adcx,4,16,0); //显示DAC寄存器值
- temp=(float)adcx*(3.3/256); //得到DAC电压值
- adcx=temp;
- LCD_ShowxNum(124,170,temp,1,16,0); //显示电压值整数部分
- temp-=adcx;
- temp*=1000;
- LCD_ShowxNum(140,170,temp,3,16,0x80); //显示电压值的小数部分
-
- adcx=Get_Adc_Average(ADC_Channel_1,20); //得到ADC转换值
- temp=(float)adcx*(3.3/4096); //得到ADC电压值
- adcx=temp;
- LCD_ShowxNum(124,190,temp,1,16,0); //显示电压值整数部分
- temp-=adcx;
- temp*=1000;
- LCD_ShowxNum(140,190,temp,3,16,0x80); //显示电压值的小数部分
- t=0;
- LED0=!LED0;
- }
- delay_ms(10);
- }
- }
pwm_dac.c函数
- //TIM1 CH1 PWM输出设置
- //PWM输出初始化
- //arr：自动重装值
- //psc：时钟预分频数
- void TIM1_PWM_Init(u16 arr,u16 psc)
- {
- GPIO_InitTypeDef GPIO_InitStructure;
- TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
- TIM_OCInitTypeDef TIM_OCInitStructure;
-
- RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE); //使能TIMx外设
- RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); //使能GPIOA外设时钟使能
-
- //设置该引脚为复用输出功能,输出TIM1 CH1的PWM脉冲波形
- GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; //TIM1_CH1
- GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //复用功能输出
- GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
- GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化GPIO
-
- TIM_TimeBaseStructure.TIM_Period = arr; //设置自动重装载周期值
- TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置预分频值 不分频
- TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
- TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数模式
- TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); //根据指定的参数初始化TIMx
-
- TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //CH1 PWM2模式
- TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
- TIM_OCInitStructure.TIM_Pulse = 0; //设置待装入捕获比较寄存器的脉冲值
- TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //OC1 低电平有效
- TIM_OC1Init(TIM1, &TIM_OCInitStructure); //根据指定的参数初始化外设TIMx
- TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable); //CH1 预装载使能
-
- TIM_ARRPreloadConfig(TIM1, ENABLE); //使能TIMx在ARR上的预装载寄存器
-
- TIM_CtrlPWMOutputs(TIM1,ENABLE); //MOE 主输出使能,高级定时器必须开启这个
-
- TIM_Cmd(TIM1, ENABLE); //使能TIMx
- }
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