超声波PIC程序

//////////////////////////////////////////////////////////////////////////////////// PIC16F877 + DYP-ME007 + 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 #include __CONFIG(0x3b32);#define trig RB0#define echo RB1void clrscn(void); // prototypesvoid cursor(char pos);void print(char *p);void setup(void);unsigned int get_srf04(void);char s[21]; // buffer used to hold text to printvoid main(void){unsigned int range;setup(); // sets up the PIC16F877 I2C portclrscn(); // clears the LCD03 displycursor(2); // sets cursor to 1st row of LCD03sprintf(s,"SRF04 Ranger Test"); // text, printed into our bufferprint(s); // send it to the LCD03while(1) { // loop foreverrange = get_srf04(); // get range from srf04 (round trip flight time in 0.8uS units)cursor(24); // sets cursor to 2nd row of LCD03sprintf(s,"Range = ?m ", range/72); // convert to cmprint(s); // send it to the LCD03cursor(44); // sets cursor to 3rd row of LCD03sprintf(s,"Range = %dinch ", range/185); // convert to inchesprint(s); // send it to the LCD03TMR1H = 0; // 52mS delay - this is so that the SRF04 ranging is not too rapidTMR1L = 0; // and the previous pulse has faded away before we start the next oneT1CON = 0x21; // 1:4 prescale and runningTMR1IF = 0;while(!TMR1IF); // wait for delay timeTMR1ON = 0; // stop timer}}unsigned int get_srf04(void){TMR1H = 0xff; // prepare timer for 10uS pulseTMR1L = -14;T1CON = 0x21; // 1:4 prescale and runningTMR1IF = 0;trig = 1; // start trigger pulsewhile(!TMR1IF); // wait 10uStrig = 0; // end trigger pulseTMR1ON = 0; // stop timerTMR1H = 0; // prepare timer to measure echo pulseTMR1L = 0;T1CON = 0x20; // 1:4 prescale but not running yetTMR1IF = 0;while(!echo && !TMR1IF); // wait for echo pulse to start (go high)TMR1ON = 1; // start timer to measure pulsewhile(echo && !TMR1IF); // wait for echo pulse to stop (go low)TMR1ON = 0; // stop timerreturn (TMR1H<<8)+TMR1L; // TMR1H:TMR1L contains flight time of the pulse in 0.8uS units}void clrscn(void){SEN = 1; // send start bitwhile(SEN); // and wait for it to clearSSPIF = 0;SSPBUF = 0xc6; // LCD02 I2C addresswhile(!SSPIF); // wait for interruptSSPIF = 0; // then clear it.SSPBUF = 0; // address of register to write towhile(!SSPIF); //SSPIF = 0; //SSPBUF = 12; // clear screenwhile(!SSPIF); //SSPIF = 0; //SSPBUF = 4; // cursor offwhile(!SSPIF); //SSPIF = 0; //PEN = 1; // send stop bitwhile(PEN); //}void cursor(char pos){SEN = 1; // send start bitwhile(SEN); // and wait for it to clearSSPIF = 0;SSPBUF = 0xc6; // LCD02 I2C addresswhile(!SSPIF); // wait for interruptSSPIF = 0; // then clear it.SSPBUF = 0; // address of register to write towhile(!SSPIF); //SSPIF = 0; //SSPBUF = 2; // set cursorwhile(!SSPIF); //SSPIF = 0; //SSPBUF = pos; // while(!SSPIF); //SSPIF = 0; //PEN = 1; // send stop bitwhile(PEN); //}void print(char *p){SEN = 1; // send start bitwhile(SEN); // and wait for it to clearSSPIF = 0;SSPBUF = 0xc6; // LCD02 I2C addresswhile(!SSPIF); // wait for interruptSSPIF = 0; // then clear it.SSPBUF = 0; // address of register to write towhile(!SSPIF); //SSPIF = 0; //while(*p) {SSPBUF = *p++; // write the datawhile(!SSPIF); //SSPIF = 0; //}PEN = 1; // send stop bitwhile(PEN); //}void setup(void){unsigned long x;TRISB = 0xfe; // RB0 (trig) is outputPORTB = 0xfe; // and starts lowTRISC = 0xff;PORTC = 0xff;SSPSTAT = 0x80;SSPCON = 0x38;SSPCON2 = 0x00;SSPADD = 50; // SCL = 91khz with 20Mhz Oscfor(x=0; x<300000L; x++); // wait for LCD03 to initialise}