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#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 }
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