DS18B20时序分析：

以下是STM32的驱动代码:

#include "bsp_ds18b20.h"static void DS18B20_GPIO_Config(void){				GPIO_InitTypeDef GPIO_InitStructure;		RCC_APB2PeriphClockCmd(DS18B20_CLK, ENABLE); 															     	GPIO_InitStructure.GPIO_Pin = DS18B20_PIN;	  	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;     	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;   	GPIO_Init(DS18B20_PORT, &GPIO_InitStructure);			GPIO_SetBits(DS18B20_PORT, DS18B20_PIN);	 }static void DS18B20_Mode_IPU(void){ 	  GPIO_InitTypeDef GPIO_InitStructure;		  GPIO_InitStructure.GPIO_Pin = DS18B20_PIN;	  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;		  GPIO_Init(DS18B20_PORT, &GPIO_InitStructure);}static void DS18B20_Mode_Out_PP(void){ 	GPIO_InitTypeDef GPIO_InitStructure;															     	GPIO_InitStructure.GPIO_Pin = DS18B20_PIN;	  	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;     	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  	GPIO_Init(DS18B20_PORT, &GPIO_InitStructure);}static void DS18B20_Rst(void){		DS18B20_Mode_Out_PP();		DS18B20_DATA_OUT(LOW);	Delay_us(750);		DS18B20_DATA_OUT(HIGH);		Delay_us(15);}static uint8_t DS18B20_Presence(void){	uint8_t pulse_time = 0;		DS18B20_Mode_IPU();		while( DS18B20_DATA_IN() && pulse_time<100 )	{		pulse_time++;		Delay_us(1);	}		if( pulse_time >=100 )		return 1;	else		pulse_time = 0;		while( !DS18B20_DATA_IN() && pulse_time<240 )	{		pulse_time++;		Delay_us(1);	}		if( pulse_time >=240 )		return 1;	else		return 0;}static uint8_t DS18B20_Read_Bit(void){	uint8_t dat;		DS18B20_Mode_Out_PP();	DS18B20_DATA_OUT(LOW);	Delay_us(10);		DS18B20_Mode_IPU();	//Delay_us(2);		if( DS18B20_DATA_IN() == SET )		dat = 1;	else		dat = 0;		Delay_us(45);		return dat;}uint8_t DS18B20_Read_Byte(void){	uint8_t i, j, dat = 0;			for(i=0; i<8; i++) 	{		j = DS18B20_Read_Bit();				dat = (dat) | (j<
    
     >1;				if (testb)		{						DS18B20_DATA_OUT(LOW);			Delay_us(8);						DS18B20_DATA_OUT(HIGH);			Delay_us(58);		}				else		{						DS18B20_DATA_OUT(LOW);			/* 60us < Tx 0 < 120us */			Delay_us(70);						DS18B20_DATA_OUT(HIGH);						Delay_us(2);		}	}}void DS18B20_Start(void){	DS18B20_Rst();	   	DS18B20_Presence();	 	DS18B20_Write_Byte(0XCC);			DS18B20_Write_Byte(0X44);	}uint8_t DS18B20_Init(void){	DS18B20_GPIO_Config();	DS18B20_Rst();		return DS18B20_Presence();}float DS18B20_Get_Temp(void){	uint8_t tpmsb, tplsb;	short s_tem;	float f_tem;		DS18B20_Rst();	   	DS18B20_Presence();	 	DS18B20_Write_Byte(0XCC);					DS18B20_Write_Byte(0X44);					DS18B20_Rst();  DS18B20_Presence();	DS18B20_Write_Byte(0XCC);				  DS18B20_Write_Byte(0XBE);					tplsb = DS18B20_Read_Byte();		 	tpmsb = DS18B20_Read_Byte(); 		s_tem = tpmsb<<8;	s_tem = s_tem | tplsb;		if( s_tem < 0 )				f_tem = (~s_tem+1) * 0.0625;		else		f_tem = s_tem * 0.0625;		return f_tem; 	}/*************************************END OF FILE******************************/