- //DS1820 C51 子程序
- //这里以11.0592M晶体为例,不同的晶体速度可能需要调整延时的时间
- //sbit DQ =P2^1;//根据实际情况定义端口
- typedef unsigned char byte;
- typedef unsigned int word;
- //延时
- void delay(word useconds)
- {
- for(;useconds>0;useconds--);
- }
- //复位
- byte ow_reset(void)
- {
- byte presence;
- DQ = 0; //pull DQ line low
- delay(29); // leave it low for 480us
- DQ = 1; // allow line to return high
- delay(3); // wait for presence
- presence = DQ; // get presence signal
- delay(25); // wait for end of timeslot
- return(presence); // presence signal returned
- } // 0=presence, 1 = no part
- //从 1-wire 总线上读取一个字节
- byte read_byte(void)
- {
- byte i;
- byte value = 0;
- for (i=8;i>0;i--)
- {
- value>>=1;
- DQ = 0; // pull DQ low to start timeslot
- DQ = 1; // then return high
- delay(1); //for (i=0; i<3; i++);
- if(DQ)value|=0x80;
- delay(6); // wait for rest of timeslot
- }
- return(value);
- }
- //向 1-WIRE 总线上写一个字节
- void write_byte(char val)
- {
- byte i;
- for (i=8; i>0; i--) // writes byte, one bit at a time
- {
- DQ = 0; // pull DQ low to start timeslot
- DQ = val&0x01;
- delay(5); // hold value for remainder of timeslot
- DQ = 1;
- val=val/2;
- }
- delay(5);
- }
- //读取温度
- char Read_Temperature(void)
- {
- union{
- byte c[2];
- int x;
- }temp;
- ow_reset();
- write_byte(0xCC); // Skip ROM
- write_byte(0xBE); // Read Scratch Pad
- temp.c[1]=read_byte();
- temp.c[0]=read_byte();
- ow_reset();
- write_byte(0xCC); //Skip ROM
- write_byte(0x44); // Start Conversion
- return temp.x/2;
- }
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