/**************************************************************************************************************
* Copyright(c) 2004 Linux-Union, Inc. All rights reserved.
* 
*Created by:	Tomy Li
*Create Date:	2004.4.15
*Reason: 		First create
*Reversion:		0.02
**************************************************************************************************************
*Module name: DS1820 function
*Description:
*				DS1820's function
*				1. Use 6MHz or 12MHz(11.0592MHz) crystal,if use other crystal, all time sequence must be modified
*				2. Read and write DS1820 IC
*				3. Use DQ to control DS1820
*-----------------------------------------------------------------------------------------------------------------
*Comments:
*	Optimizition level:	8(with speed)				
*---------------------------------------------------------------------------------------------------------------
*History:
*	1. Modify all constant variable to upper case, replace some constant to predefined symbol.  2004-09-19
*/

#define byte unsigned char
#define uint unsigned int

//Define DS1820's command
#define SKIP_ROM 0XCC			//Skip 64bits serial number
#define READ_SCRATCH_PAD 0XBE	//Read 9 bytes register data
#define START_CONVERSION 0X44	//Start temperature conversion
#define MATCH_ROM 0X55			//The match ROM command followed by a 64¨Cbit ROM code sequence allows the bus 											//master to address a specific slave device on a multi-drop or single-drop bus.
#define READ_ROM 0X33			//This command can only be used when there is one slave on the bus. It allows the 										//bus master to read the slave¡¯s 64-bit ROM code without using the Search ROM procedure.
#define SERACH_ROM 0XF0			//Allows the master to determine the number of slaves and their device types.
#define ALARM_SERACH 0XEC		//This command allows the master device to determine if any DS18S20s experienced an alarm								// condition during the most recent temperature conversion.
#define COPY_SCRATCH_PAD 0X48	//This command copies the contents of the scratchpad TH and TL registers (bytes 2 and 3) 								//to EEPROM.
#define WRITE_SCRATCH_PAD 0X4E	//This command allows the master to write 2 bytes of data to the DS18S20¡¯s scratchpad.
#define RECALL_EEPROM 0XB8		//This command recalls the alarm trigger values (TH and TL) from EEPROM and places the 									//data in bytes 2 and 3.
#define READ_POWER 0XB4			//The master can use this command to determine if any DS18S20s on the bus are using 									//parasite power.
//------------------------------------------------------------------------
#define LEVEL_HIGH	1
#define LEVEL_LOW	0
/*
#define true	1
#define false	0



//
#define UI8_T unsigned char
#define UI16_T  unsigned int
#define I8_T char
#define BOOL bit
*/


//sbit	DQ =DS1820_DQ;


/*****************************************************
Function: Dly10us
Description: Delay specified number of 10us 
Parameters: us, number need to delay
Return value: None
******************************************************/
void Dly10us(UI8_T us)
{
	while(us--);		//5 mechine cycle, 10us
}

/**********************************************************************************
Function: write_1820
Description: write data ds1820
Parameter: cmd, command of ds1820
Return value: None 
************************************************************************************/
void Write_1820(UI8_T val)
{
	UI8_T i;
	for (i=8; i>0; i--) // writes byte, one bit at a time
	{
		DQ = LEVEL_LOW; 		// pull DQ low to start timeslot
		DQ = val&0x01;
		Dly10us(6); 	// hold value for remainder of timeslot. 60us
		DQ =LEVEL_HIGH;
		val=val/2;		//val shift right 1 bit	
	}
}
/**********************************************************************************
Function: read_1820
Description: read one byte data from ds1820
Parameter: void
Return value: read data
************************************************************************************/
UI8_T Read_1820(void)
{
	UI8_T i;
	UI8_T value = 0;
	for (i=8;i>0;i--)
	{
		value>>=1;		
		DQ = LEVEL_LOW; 		// pull DQ low to start timeslot
		DQ = LEVEL_HIGH; 		// then return high
		DQ=LEVEL_HIGH;
		DQ=LEVEL_HIGH;
		DQ=LEVEL_HIGH;
		DQ=LEVEL_HIGH;
		if(DQ) value|=0x80;	//read bit at 13us. This is very important
		Dly10us(5); // wait for rest of timeslot
	}
	return(value);
}
/**********************************************************************************
Function: rst_1820
Description: reset ds1820
Parameter: None
Return value: If present, return 0, otherwise return 1 
************************************************************************************/
BOOL Rst_1820(void)
{
  BOOL presence;
  DQ = LEVEL_LOW; 			//pull DQ line low
  Dly10us(48); 	// remain it low for 480us min(max 960us)
  DQ =LEVEL_HIGH; 			// allow line to return high
  Dly10us(6); 		// wait for presence 15-60us
  presence = DQ; 	// get presence signal
  Dly10us(42); 	// wait for end of timeslot about 420us(480-60)
  return(presence); // presence signal returned
}