ds18b20 驱动程序 多点测量 crc校验

#include <avr/io.h> #include <util/delay.h> #include "ds18b20.h" const prog_uchar matchrom[24]={ 0x28,0x19,0x57,0x21,0x02,0x00,0x00,0xa7, 0x28,0xec,0x47,0x21,0x02,0x00,0x00,0x42, 0x28,0x0d,0x61,0x21,0x02,0x00,0x00,0x38}; static void delay_nus(unsigned int n) //N us延时函数 { unsigned int i=0; for (i=0;i<n;i++) _delay_us(1); } static void delay_nms(unsigned int n) //N ms延时函数 { unsigned int i=0; for (i=0;i<n;i++) _delay_ms(1); } unsigned char test_ds18b20(void) { unsigned char i; SET_DIR_1WIRE; //设置PA2 为输出 SET_OP_1WIRE; delay_nus(2); CLR_OP_1WIRE; delay_nus(480); //480us以上 SET_OP_1WIRE; CLR_DIR_1WIRE; delay_nus(80); if(CHECK_IP_1WIRE) i = 0; else i = 1; SET_DIR_1WIRE; SET_OP_1WIRE; delay_nus(240); //60~240us return i; } void init_1820(void)//复位函数 { SET_DIR_1WIRE; //设置PA2 为输出 SET_OP_1WIRE; delay_nus(2); CLR_OP_1WIRE; delay_nus(480); //480us以上 SET_OP_1WIRE; CLR_DIR_1WIRE; delay_nus(20); //15~60us while(CHECK_IP_1WIRE); SET_DIR_1WIRE; SET_OP_1WIRE; delay_nus(240); //60~240us } void write_1820(unsigned char x) { unsigned char m; for(m=0;m<8;m++) { CLR_OP_1WIRE; delay_nus(2); if(x&(1<<m)) //写数据了，先写低位的！ SET_OP_1WIRE; else {CLR_OP_1WIRE;} delay_nus(60); //15~60us SET_OP_1WIRE; delay_nus(5); } } unsigned char read_1820(void) { unsigned char temp,k,n; temp=0; for(n=0;n<8;n++) { CLR_OP_1WIRE; _delay_us(2); SET_OP_1WIRE; CLR_DIR_1WIRE; delay_nus(8); k=(CHECK_IP_1WIRE); //读数据,从低位开始 if(k) temp|=(1<<n); else temp&=~(1<<n); delay_nus(60); SET_DIR_1WIRE; } return (temp); } void start(void)//全部开始转换 { init_1820(); write_1820(0xcc); write_1820(0x44); delay_nms(800); } /************************************************************ 此函数用于读取指定ds18b20的温度，返回值的低字节存储整数部分， 高字节低四位存储小数部分，不含符号位 ***************************************************************/ unsigned int gettemp(unsigned char number) { volatile unsigned char temh,teml,wm0,wm1,wm2,wm3; unsigned int temp = 0; start(); match_rom(number); write_1820(0xbe); //发出读命令 teml=read_1820(); temh=read_1820(); //读数据 wm0=teml>>4; wm1=temh<<4; wm2=wm1+wm0; wm3=wm2/100; temp = (10 * ((unsigned int)teml & 0x0f) / 16) << 8;//取温度的小数0.1位的数字 temp |= (unsigned int)(wm2 & 0xff);//取温度的整数部分 return temp; } /*********************************************** 此函数用于读取当前ds18b20中64位rom的值，存入readrom中 ************************************************/ /* void read_rom(void) { unsigned char i; init_1820(); //复位18b20 write_1820(0x33); //写读rom命令 for(i=0;i<8;i++) readrom[i]=read_1820(); } */ /******************************************** 此函数用于读取指定ds18b20中9字节ram的值，存入readram中 *******************************************************/ void read_ram(unsigned char number) { unsigned char i; loop: match_rom(number); write_1820(0xbe); for(i=0;i<9;i++) readram[i]=read_1820(); i=DS18B20_CheckCRC8(readram,9); if(i!=0x01) goto loop; } /********************************************** 此函数用于匹配指定ds18b20的64位rom， 之后可进行相关读写操作等。 **************************************************/ void match_rom(unsigned char number) { unsigned char i; volatile char j; init_1820(); write_1820(0x55); for(i=0;i<8;i++) { j=pgm_read_byte(matchrom+i+8*number); write_1820(j); } } /*************************************************** 向指定ds18b20中写入TH，和Tl 并copy到eeram中 ****************************************************/ void write_ram(unsigned char temph,unsigned char templ,unsigned char num) { match_rom(num); write_1820(0x4e); write_1820(temph); write_1820(templ); write_1820(0x48); delay_nms(10); } unsigned char CRCValue(unsigned char NewData,unsigned char CRCData) { unsigned char bitValue; // unsigned char TempValue; //模拟CRC硬件内部的8位数据寄存器 unsigned char i; for(i=0; i<8; i++) { //新数据位与CRC寄存器的内容的D0位的异或值作为内部通道的输入 bitValue = (NewData ^ CRCData)& 0x01; //执行X4、X5的异或操作 if(bitValue==0x01) { TempValue = CRCData ^ 0x18; } else { TempValue = CRCData; } //CRC寄存器无进位右移 TempValue >>= 1; //补上进位位，即D0位 if(bitValue==0x01) { CRCData = TempValue | 0x80; } else { CRCData = TempValue; } //为处理下一位作准备 NewData >>= 1; } return CRCData; } /***************************************************************** 此函数用于CRC校验，DataLength为长度，Databuff为缓存区 ******************************************************************/ unsigned char DS18B20_CheckCRC8(unsigned char *DataBuff,unsigned char DataLength) { volatile unsigned char CRCData; unsigned char i; CRCData = 0; for(i=0; i<DataLength; i++) { CRCData = CRCValue(DataBuff[i],CRCData); } if(CRCData == 0) { return 0x01; } else { return 0; } }