////////////////////////////////////////////////////////////////////////////////
//
// 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
}