51 MCU HCSR04 ultrasonic rangefinder basic code

  1 /************************************************ *************************************************** *********/
  2 //HC-SR04 Ultrasonic Distance Measurement Module DEMO Program
  3 //Crystal: 11.0592
  4 // Wiring: module TRIG connects to P1.2 ECH0 connects to P1.1
  5 //Serial port baud rate 9600
  6/************************************************ *************************************************** *********/      
  7 #include 
  8 #include 
  9 #include 
 10
 11 #define uchar unsigned char
 12 #define uint unsigned int  
 13 #define RX P1_1
 14 #define TX P1_2
 15
 16
 17 unsigned int time=0;
 18 unsigned int timer=0;
 19 float S=0;
 20 bit flag =0;
 twenty one
 twenty two
 twenty three /************************************************ **********/
 24 void Conut(void)
 25 {
 26 time=TH0*256+TL0;
 27 TH0=0;
 28 TL0=0;
 29 S=(time*1.87)/100; //The calculated value is CM
 30 if(flag==1) //Out of measurement
 31 {
 32 flag=0;
 33 printf("--\n");
 34 }    
 35 printf("S=%f\n",S);
 36 }
 37 /************************************************ **********/
 38 void delayms(unsigned int ms)
 39 {
 40 unsigned char i=100,j;
 41 for(;ms;ms--)
 42 {
 43 while(--i)
 44 {
 45 j=10;
 46 while(--j);
 47 }
 48 }
 49 }
 50 /************************************************ **********/
 51 void zd0() interrupt 1 //T0 interrupt is used for counter overflow, exceeding the ranging range
 52 {
 53 flag=1; //interrupt overflow flag
 54 }
 55 /************************************************ **********/
 56 void StartModule() //T1 interrupt is used to scan the digital tube and count 800MS to start the module
 57 {
 58 TX=1; //800MS start the module once
 59 _nop_();
 60 _nop_();
 61 _nop_();
 62 _nop_();
 63 _nop_();
 64 _nop_();
 65 _nop_();
 66 _nop_();
 67 _nop_();
 68 _nop_();
 69 _nop_();
 70 _nop_();
 71 _nop_();
 72 _nop_();
 73 _nop_();
 74 _nop_();
 75 _nop_();
 76 _nop_();
 77 _nop_();
 78 _nop_();
 79 _nop_();
 80 TX=0;
 81 }
 82 /************************************************ **********/
 83 void main(void)
 84 {  
 85 TMOD=0x21; //Set T0 to mode 1, GATE=1;
 86 SCON=0x50;
 87 TH1=0xFD;
 88 TL1=0xFD;
 89 TH0=0;
 90 TL0=0;
 91 TR0=1;  
 92 ET0=1; //Enable T0 interrupt
 93 TR1=1; //Start the timer
 94 TI=1;
 95     
 96 EA=1; // Enable general interrupt
 97     
 98     
 99 while(1)
100 {
101 StartModule();
102 while(!RX); //Wait when RX is zero
103 TR0=1; //Start counting
104 while(RX); //When RX is 1, count and wait
105 TR0=0; //Close counting
106 Conut(); //Calculation
107 delayms(10); //100MS
108 }
109 }