////////////////////////////////////////////////////////////////////////////////
//
//     PIC16F877 + SRF08 + LCD03 example
//     Written October 2005 by Gerald Coe, using HITECH PIC16 compiler
// 
//		 Performs ranging using same I2C bus as the LCD03 is using
//		 Note - assumes a 20MHz crystal
//		 
//     This code is Freeware - Use it for any purpose you like.
//
///////////////////////////////////////////////////////////////////////////////


#include <pic.h>
#include <stdio.h>
	 
__CONFIG(0x3b32);								// configuration register - see PIC data sheet for details		

#define SRF08_ADDR	0xE0					// Factory supplied default address

void clrscn(void);							// prototypes
void cursor(char pos);
void print(char *p);
void setup(void);
unsigned int get_srf08(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,"SRF08 Ranger Test");		// text, printed into our buffer
	print(s);									// send it to the LCD03

	while(1) {									// loop forever
		range = get_srf08();					// get range from srf08 (round trip flight time in 1uS units)
		cursor(24);								// sets cursor to 2nd row of LCD03
		sprintf(s,"Range = %dcm  ", range/58);	// convert to cm
		print(s);								// send it to the LCD03	
		cursor(44);								// sets cursor to 3rd row of LCD03
		sprintf(s,"Range = %dinch  ", range/148);	// convert to inches
		print(s);								// send it to the LCD03	
	}
}

unsigned int get_srf08(void)
{
unsigned int range;

// This 1st part send the ranging command to the SRF08 to start it ranging
	SEN = 1;										// send start bit
	while(SEN);									// and wait for it to clear
	SSPIF = 0;
	SSPBUF = SRF08_ADDR;						// SRF08 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 = 82;								// range in uS command
	while(!SSPIF);								// 
	SSPIF = 0;									//
	PEN = 1;										// send stop bit
	while(PEN);									//

// now wait for the ranging to complete. This delay is a little over 100mS but 
// can be reduced to 66ms if required.
	TMR1H = 0;									// delay while the srf08 is ranging
	TMR1L = 0;							
	T1CON = 0x31;								// 1:8 prescale and running (1.6uS/clk)
	TMR1IF = 0;
	while(!TMR1IF);							// wait for delay time
	TMR1ON = 0;									// stop timer	
	
// finally get the range from the SRF08
	SEN = 1;										// send start bit
	while(SEN);									// and wait for it to clear
	ACKDT = 0;									// acknowledge bit
	SSPIF = 0;
	SSPBUF = SRF08_ADDR;						// SRF08 I2C address
	while(!SSPIF);								// wait for interrupt
	SSPIF = 0;									// then clear it.
	SSPBUF = 2;									// address of register to read from - high byte of result 
	while(!SSPIF);								// 
	SSPIF = 0;									//
	RSEN = 1;									// send repeated start bit
	while(RSEN);								// and wait for it to clear
	SSPIF = 0;									//
	SSPBUF = SRF08_ADDR+1;					// SRF08 I2C address - the read bit is set this time
	while(!SSPIF);								// wait for interrupt
	SSPIF = 0;									// then clear it.
	RCEN = 1;									// start receiving
	while(!STAT_BF);							// wait for high byte of range
	range = SSPBUF<<8;						// and get it
	ACKEN = 1;									// start acknowledge sequence
	while(ACKEN);								// wait for ack. sequence to end
	RCEN = 1;									// start receiving
	while(!STAT_BF);							// wait for low byte of range
	range += SSPBUF;							// and get it
	ACKDT = 1;									// not acknowledge for last byte
	ACKEN = 1;									// start acknowledge sequence
	while(ACKEN);								// wait for ack. sequence to end
	PEN = 1;										// send stop bit
	while(PEN);									//
	return range;
}

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;

	PORTB = 0xfe;						// RB0 (trig) is output
	TRISB = 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		
}