1wire.c

/*********************************************************************
 *
 *                 1-Wire Communication Protocol
 *
 *********************************************************************
 * FileName:        1wire.c
 * Dependencies:
 * Processor:       PIC18
 * Complier:        MCC18 v3.13
 * Company:         Microchip Technology, Inc.
 *
 * Software License Agreement
 *
 * Copyright © 2004-2007 Microchip Technology Inc.  All rights reserved.
 *
 * Microchip licenses to you the right to use, copy and distribute Software 
 * only when embedded on a Microchip microcontroller or digital signal 
 * controller and used with a Microchip radio frequency transceiver, which 
 * are integrated into your product or third party product (pursuant to the 
 * sublicense terms in the accompanying license agreement).  You may NOT 
 * modify or create derivative works of the Software.  
 *
 *
 * You should refer to the license agreement accompanying this Software for 
 * additional information regarding your rights and obligations.
 *
 * SOFTWARE AND DOCUMENTATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY 
 * KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION, ANY WARRANTY 
 * OF MERCHANTABILITY, TITLE, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR 
 * PURPOSE. IN NO EVENT SHALL MICROCHIP OR ITS LICENSORS BE LIABLE OR OBLIGATED 
 * UNDER CONTRACT, NEGLIGENCE, STRICT LIABILITY, CONTRIBUTION, BREACH OF 
 * WARRANTY, OR OTHER LEGAL EQUITABLE THEORY ANY DIRECT OR INDIRECT DAMAGES OR 
 * EXPENSES INCLUDING BUT NOT LIMITED TO ANY INCIDENTAL, SPECIAL, INDIRECT, 
 * PUNITIVE OR CONSEQUENTIAL DAMAGES, LOST PROFITS OR LOST DATA, COST OF 
 * PROCUREMENT OF SUBSTITUTE GOODS, TECHNOLOGY, SERVICES, OR ANY CLAIMS BY 
 * THIRD PARTIES (INCLUDING BUT NOT LIMITED TO ANY DEFENSE THEREOF), OR OTHER 
 * SIMILAR COSTS.
 *
 * Author               Date        Comment
 *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Sasha     			12/20/07    Original
 ********************************************************************/

 /****** I N C L U D E S **********************************************************/
#include "Config.h"
#include "1wire.h"
#include "var.h"

//****** V A R I A B L E S ********************************************************/
unsigned char macro_delay;
unsigned int raw_temp;
char *temp = "000.00 C";
/**********************************************************************
* Function:        void drive_OW_low (void)
* PreCondition:    None
* Input:		   None	
* Output:		   None	
* Overview:		   Configure the OW_PIN as Output and drive the OW_PIN LOW.	
***********************************************************************/
void drive_OW_low (void)
{
	OW_PIN_DIRECTION = OUTPUT;
	OW_WRITE_PIN=LOW;
}

/**********************************************************************
* Function:        void drive_OW_high (void)
* PreCondition:    None
* Input:		   None	
* Output:		   None	
* Overview:		   Configure the OW_PIN as Output and drive the OW_PIN HIGH.	
***********************************************************************/
void drive_OW_high (void)
{
	OW_PIN_DIRECTION = OUTPUT;
	OW_WRITE_PIN = HIGH;	
}

/**********************************************************************
* Function:        unsigned char read_OW (void)
* PreCondition:    None
* Input:		   None	
* Output:		   Return the status of OW pin.	
* Overview:		   Configure as Input pin and Read the status of OW_PIN 	
***********************************************************************/
unsigned char read_OW (void)
{
	unsigned char read_data=0;
	
	OW_WRITE_PIN = INPUT;

	 if (HIGH == OW_READ_PIN)
	 	read_data = SET;
	 else 	
		read_data = CLEAR;
		
	return read_data;
}

/**********************************************************************
* Function:        unsigned char OW_reset_pulse(void)
* PreCondition:    None
* Input:		   None	
* Output:		   Return the Presense Pulse from the slave.	
* Overview:		   Initialization sequence start with reset pulse.
*				   This code generates reset sequence as per the protocol
***********************************************************************/
unsigned char OW_reset_pulse(void)
{
	unsigned char presence_detect;
	
  	drive_OW_low(); 				// Drive the bus low
 	
 	wait(DELAY_240Us);	  			// delay 480 microsecond (us)
	wait(DELAY_240Us);		

 	drive_OW_high ();  				// Release the bus
	
	wait(DELAY_70Us);				// delay 70 microsecond (us)
	
	presence_detect = read_OW();	//Sample for presence pulse from slave

 	wait(DELAY_205Us);	  			// delay 410 microsecond (us)
	wait(DELAY_205Us);		
	
	drive_OW_high ();		    	// Release the bus
	
	return presence_detect;
}	

/**********************************************************************
* Function:        void OW_write_bit (unsigned char write_data)
* PreCondition:    None
* Input:		   Write a bit to 1-wire slave device.
* Output:		   None
* Overview:		   This function used to transmit a single bit to slave device.
*				   
***********************************************************************/

void OW_write_bit (unsigned char write_bit)
{
	if (write_bit)
	{
		//writing a bit '1'
		drive_OW_low(); 				// Drive the bus low
		wait(DELAY_6Us);				// delay 6 microsecond (us)
		drive_OW_high ();  				// Release the bus
		wait(DELAY_64Us);				// delay 64 microsecond (us)
	}
	else
	{
		//writing a bit '0'
		drive_OW_low(); 				// Drive the bus low
		wait(DELAY_60Us);				// delay 60 microsecond (us)
		drive_OW_high ();  				// Release the bus
		wait(DELAY_10Us);				// delay 10 microsecond for recovery (us)
	}
}	


/**********************************************************************
* Function:        unsigned char OW_read_bit (void)
* PreCondition:    None
* Input:		   None
* Output:		   Return the status of the OW PIN
* Overview:		   This function used to read a single bit from the slave device.
*				   
***********************************************************************/

unsigned char OW_read_bit (void)
{
	unsigned char read_data; 
	//reading a bit 
	drive_OW_low(); 						// Drive the bus low
	wait(DELAY_6Us);						// delay 6 microsecond (us)
	drive_OW_high ();  						// Release the bus
	wait(DELAY_9Us);						// delay 9 microsecond (us)

	read_data = read_OW();					//Read the status of OW_PIN

	wait(DELAY_55Us);						// delay 55 microsecond (us)	
	return read_data;
}

/**********************************************************************
* Function:        void OW_write_byte (unsigned char write_data)
* PreCondition:    None
* Input:		   Send byte to 1-wire slave device
* Output:		   None
* Overview:		   This function used to transmit a complete byte to slave device.
*				   
***********************************************************************/
void OW_write_byte (unsigned char write_data)
{
	unsigned char loop;
	
	for (loop = 0; loop < 8; loop++)
	{
		OW_write_bit(write_data & 0x01); 	//Sending LS-bit first
		write_data >>= 1;					// shift the data byte for the next bit to send
	}	
}	

/**********************************************************************
* Function:        unsigned char OW_read_byte (void)
* PreCondition:    None
* Input:		   None
* Output:		   Return the read byte from slave device
* Overview:		   This function used to read a complete byte from the slave device.
*				   
***********************************************************************/

unsigned char OW_read_byte (void)
{
	unsigned char loop, result=0;
	
	for (loop = 0; loop < 8; loop++)
	{
		
		result >>= 1; 				// shift the result to get it ready for the next bit to receive
		if (OW_read_bit())
		result |= 0x80;				// if result is one, then set MS-bit
	}
	return result;					
}	

/**********************************************************************
* Function:        char* ds18b20_readtemp(void)
* PreCondition:    None
* Input:		   None
* Output:		   string store temperatue value which is convered
* Overview:		   This function used to read temperatue value of device.
*				   
***********************************************************************/

char* ds18b20_readtemp(void)
{
	OW_reset_pulse();                         	// Onewire reset signal
	OW_write_byte(0xCC);                   		// Issue command SKIP_ROM
	OW_write_byte(0x44);                   		// Issue command CONVERT_T
	
	while(OW_read_byte() == 0) ;
	
	OW_reset_pulse();                         	// Onewire reset signal
	OW_write_byte(0xCC);                   		// Issue command SKIP_ROM
	OW_write_byte(0xBE);                   		// Issue command READ_SCRATCHPAD
	
	raw_temp  = OW_read_byte();              			// Read temperature LSB byte
	raw_temp |= ((unsigned int)OW_read_byte() << 8);       	// Read temperature MSB byte
	
	if(raw_temp & 0x8000) {                       // If the temperature is negative
	  temp[0] = '-';                              // Put minus sign (-)
	  raw_temp = ~raw_temp + 1;                   // Change temperature value to positive form
	}
	else {
	  if((raw_temp >> 4) >= 100)                  // If the temperatue >= 100 °C
		temp[0] = '1';                            // Put 1 of hundreds
	  else                                        // otherwise
		temp[0] = ' ';                            // put space ' '
	}
 
	//Put the first two digits ( for tens and ones)
	temp[1] = ( (raw_temp >> 4) / 10 ) % 10 + 48;      // Put tens digit
	temp[2] =   (raw_temp >> 4)        % 10  + 48;     // Put ones digit
	temp[3] = '.';
	//Put the 4 fraction digits (digits after the point)
	//Why 625: because we're working with 12-bit resolution
	temp[4] = ( (raw_temp & 0x0F) * 625) / 1000 + 48;          // Put thousands digit
	temp[5] = (((raw_temp & 0x0F) * 625) / 100 ) % 10 + 48;    // Put hundreds digit
	//temp[6] = (((raw_temp & 0x0F) * 625) / 10 )  % 10 + 48;    // Put tens digit
	//temp[7] = ( (raw_temp & 0x0F) * 625) % 10 + 48;            // Put ones digit
 
	temp[6] = 223;                                	// Put degree symbol ( ° )
	temp[7] = 'C';
	return temp;
}

/********************************************************************************************
                  E N D     O F     1 W I R E . C  
*********************************************************************************************/