利用定时器3产生pwm波，使能超声波模块。利用定时器4计时，计算出时间。
单片机源程序如下:
- #include "led.h"
- #include "delay.h"
- #include "key.h"
- #include "sys.h"
- #include "oled.h"
- #include "SR04.h"
- #include "usart.h"
-
- /************************************************
- 时间：2019.7.25
- 作者：菜鸡
- 利用定时器TIM3的PWM输出得到触发信号
- TIM4用于计算回响电平输出时间
- ************************************************/
-
- void Count(void);
- uint32_t Distance;
- uint16_t Time;
- uint8_t ShowData[5]={0,0,0,0,0};
- int main(void)
- {
- delay_init(); //延时函数初始化
- LED_Init(); //LED端口初始化
- OLED_Init(); //初始化OLED
- Uitr_GPIO_Config();
- OLED_ShowString(0,0,"now:",24);
- OLED_ShowString(50,0,"unknow",24);
- OLED_ShowString(0,24,"distance:",16);
- OLED_ShowString(53,40,"mm",24);
- OLED_Refresh_Gram(); //更新显示到OLED
- 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
- TIM3_PWM_Init(999,7199); //不分频。PWM频率=72000000/900=80Khz
- TIM4_Config();
- while(1)
- {
- TIM_SetCompare2(TIM3,1);
- while(ECHO_IN != 1);
- TIM_Cmd(TIM4,ENABLE); //计数器开始计数
- while(ECHO_IN == 1);
- TIM_Cmd(TIM4,DISABLE); //计数器停止计数
- Count();
- }
-
- }
-
- void Count(void)
- {
- Time = TIM4->CNT; //读计数器值
- TIM4->CNT = 0; //清除计数器
- if(Time>23530) //判断是否在4M范围，超出显示ERRO
- {
- OLED_ShowString(50,0,"failed",24);
- OLED_Refresh_Gram(); //更新显示到OLED
- }
- else
- {
- Distance = (uint32_t)(Time*340/2/1000) ; //计算出来的是MM
- ShowData[0] = (Distance%10000/1000)+'0';
- ShowData[1] = (Distance%1000/100)+'0';
- ShowData[2] = (Distance%100/10)+'0';
- ShowData[3] = (Distance%10/1)+'0';
- OLED_ShowString(50,0,"normal",24);
- OLED_ShowString(0,40,ShowData,24);
- OLED_Refresh_Gram(); //更新显示到OLED
- }
-
- }
所有资料51hei提供下载:
HC-SR04超声波测距.7z
(197.2 KB, 下载次数: 60)
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