我有一张图18F4550如何读取超声波传感器的距离。

Question

我有PIC18f4550，需要用picBasic pro编写代码。

我正在连接直流电机，超声波传感器和红外传感器.等

我已经做了所有的事情，但仍然对如何连接超声波传感器感到困惑。

这里是PIC中的超声波引脚

trisb.3=0    'trigger ultrasound
trisb.4=1    ' Echo from Ultrasound

我需要一个示例代码

Answer 1

编写程序的基本步骤:

1-为超声波模块提供触发器

2-听回声

3-接收回波高时启动定时器

4-当回声变低时停止计时器

5-读取计时器值

6-将其转换为距离

7-展示它

距离计算

• 距离=速度*时间
• 假设超声波传感器与目标之间的距离。
• 超声波脉冲传播的总距离: 2d (向前和向后)
• 空气中声速: 340米/秒= 34000厘米/秒
• 因此，d= (34000* Time )/2，其中时间= (TMR1H:TMR1L)/(1000000)
• 因此，d= (TMR1H:TMR1L)/58.82 cm
• TMR1H:TMR1L = TMR1L x (TMR1H<<8)

MikroC码

// LCD module connections
sbit LCD_RS at RD2_bit;
sbit LCD_EN at RD3_bit;
sbit LCD_D4 at RD4_bit;
sbit LCD_D5 at RD5_bit;
sbit LCD_D6 at RD6_bit;
sbit LCD_D7 at RD7_bit;

sbit LCD_RS_Direction at TRISD2_bit;
sbit LCD_EN_Direction at TRISD3_bit;
sbit LCD_D4_Direction at TRISD4_bit;
sbit LCD_D5_Direction at TRISD5_bit;
sbit LCD_D6_Direction at TRISD6_bit;
sbit LCD_D7_Direction at TRISD7_bit;
// End LCD module connections

void main()
{
  int a;
  char txt[7];
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);          // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);     // Cursor off

  TRISB = 0b00010000;           //RB4 as Input PIN (ECHO)

  Lcd_Out(1,1,"Developed By");
  Lcd_Out(2,1,"Mina Karam");

  Delay_ms(3000);
  Lcd_Cmd(_LCD_CLEAR);

  T1CON = 0x10;                 //Initialize Timer Module

  while(1)
  {
    TMR1H = 0;                  //Sets the Initial Value of Timer
    TMR1L = 0;                  //Sets the Initial Value of Timer

    PORTB.F0 = 1;               //TRIGGER HIGH
    Delay_us(10);               //10uS Delay
    PORTB.F0 = 0;               //TRIGGER LOW

    while(!PORTB.F4);           //Waiting for Echo
    T1CON.F0 = 1;               //Timer Starts
    while(PORTB.F4);            //Waiting for Echo goes LOW
    T1CON.F0 = 0;               //Timer Stops

    a = (TMR1L | (TMR1H<<8));   //Reads Timer Value
    a = a/58.82;                //Converts Time to Distance
    a = a + 1;                  //Distance Calibration
    if(a>=2 && a<=400)          //Check whether the result is valid or not
    {
      IntToStr(a,txt);
      Ltrim(txt);
      Lcd_Cmd(_LCD_CLEAR);
      Lcd_Out(1,1,"Distance = ");
      Lcd_Out(1,12,txt);
      Lcd_Out(1,15,"cm");
    }
    else
    {
      Lcd_Cmd(_LCD_CLEAR);
      Lcd_Out(1,1,"Out of Range");
    }
    Delay_ms(400);
  }
}