超声波模块SRF05

//
//     PIC16F877 + HY-SRF05 + LCD03 example
//     Written October 2008 , using HITECH PIC16 compiler
// 
// Note - assumes a 20MHz crystal, which is 5MHz timer clock
// A 1:4 prescaler is used to give a 1.25MHz timer count (0.8uS per tick)
//
//     This code is Freeware - Use it for any purpose you like.
//
///
#include <pic.h>
#include <stdio.h>
__CONFIG(0x3b32); 
#define trig RB0
#define echo RB1
void clrscn(void); // prototypes
void cursor(char pos);
void print(char *p);
void setup(void);
unsigned int get_srf04(void);
char s[21]; // buffer used to hold text to print
void main(void)
{
    unsigned int range;
    setup(); // sets up the PIC16F877 I2C port
    clrscn(); // clears the LCD03 disply
    cursor(2); // sets cursor to 1st row of LCD03
    sprintf(s,"SRF04 Ranger Test");// text, printed into our buffer
    print(s); // send it to the LCD03
    while(1) 
    { // loop forever
        range = get_srf04();// get range from srf04 (round trip flight time in 0.8uS units)
        cursor(24); // sets cursor to 2nd row of LCD03
        sprintf(s,"Range = %dcm  ", range/72);// convert to cm
        print(s); // send it to the LCD03 
        cursor(44); // sets cursor to 3rd row of LCD03
        sprintf(s,"Range = %dinch  ", range/185);// convert to inches
        print(s); // send it to the LCD03 
        TMR1H = 0; // 52mS delay - this is so that the SRF04 ranging is not too rapid
        TMR1L = 0; // and the previous pulse has faded away before we start the next one
        T1CON = 0x21; // 1:4 prescale and running
        TMR1IF = 0;
        while(!TMR1IF);// wait for delay time
        TMR1ON = 0; // stop timer 
    }
}
unsigned int get_srf04(void)
{
    TMR1H = 0xff; // prepare timer for 10uS pulse
    TMR1L = -14;
    T1CON = 0x21; // 1:4 prescale and running
    TMR1IF = 0; 
    trig = 1; // start trigger pulse
    while(!TMR1IF);// wait 10uS
    trig = 0; // end trigger pulse
    TMR1ON = 0; // stop timer
    TMR1H = 0; // prepare timer to measure echo pulse
    TMR1L = 0;
    T1CON = 0x20; // 1:4 prescale but not running yet
    TMR1IF = 0;
    while(!echo && !TMR1IF);// wait for echo pulse to start (go high)
    TMR1ON = 1; // start timer to measure pulse
    while(echo && !TMR1IF);// wait for echo pulse to stop (go low)
    TMR1ON = 0; // stop timer
    return (TMR1H<<8)+TMR1L;// TMR1H:TMR1L contains flight time of the pulse in 0.8uS units
}
void clrscn(void)
{
    SEN = 1; // send start bit
    while(SEN); // and wait for it to clear
    SSPIF = 0;
    SSPBUF = 0xc6;// LCD02 I2C address
    while(!SSPIF);// wait for interrupt
    SSPIF = 0; // then clear it.
    SSPBUF = 0; // address of register to write to 
    while(!SSPIF);// 
    SSPIF = 0; //
    SSPBUF = 12; // clear screen 
    while(!SSPIF);// 
    SSPIF = 0; //
    SSPBUF = 4; // cursor off 
    while(!SSPIF);// 
    SSPIF = 0; //
    PEN = 1; // send stop bit
    while(PEN); //
}
void cursor(char pos)
{
    SEN = 1; // send start bit
    while(SEN); // and wait for it to clear
    SSPIF = 0;
    SSPBUF = 0xc6;// LCD02 I2C address
    while(!SSPIF);// wait for interrupt
    SSPIF = 0; // then clear it.
    SSPBUF = 0; // address of register to write to 
    while(!SSPIF);// 
    SSPIF = 0; //
    SSPBUF = 2; // set cursor 
    while(!SSPIF);// 
    SSPIF = 0; //
    SSPBUF = pos; //  
    while(!SSPIF);// 
    SSPIF = 0; //
    PEN = 1; // send stop bit
    while(PEN); //
}
void print(char *p)
{
    SEN = 1; // send start bit
    while(SEN); // and wait for it to clear
    SSPIF = 0;
    SSPBUF = 0xc6;// LCD02 I2C address
    while(!SSPIF);// wait for interrupt
    SSPIF = 0; // then clear it.
    SSPBUF = 0; // address of register to write to 
    while(!SSPIF);// 
    SSPIF = 0; //
    while(*p) 
    {
        SSPBUF = *p++;// write the data 
        while(!SSPIF);// 
        SSPIF = 0; // 
    }
    PEN = 1; // send stop bit
    while(PEN); //
}
void setup(void)
{
    unsigned long x;
    TRISB = 0xfe; // RB0 (trig) is output
    PORTB = 0xfe; // and starts low
    TRISC = 0xff;
    PORTC = 0xff;
    SSPSTAT = 0x80;
    SSPCON = 0x38;
    SSPCON2 = 0x00;
    SSPADD = 50; // SCL = 91khz with 20Mhz Osc
    for(x=0; x<300000L; x++);// wait for LCD03 to initialise 
}