OneWire应用 单总线温度传感器DS18系列

OneWire DS18S20, DS18B20, DS1822 Temperature

DS18B20

The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile user programmable upper and lower trigger points. The DS18B20 communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C. In addition, the DS18B20 can derive power directly from the data line (“parasite power”), eliminating the need for an external power supply.  分辨率9-12位，可设置报警，适用于1-Wire 总线，测量温度-55-125摄氏度
Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.  一个控制器可连接多个传感器，可应用于许多领域

FEATURES 特点
§ Unique 1-Wire Interface Requires Only One Port Pin for Communication
§ Each Device has a Unique 64-Bit Serial Code Stored in an On-Board ROM
§ Multidrop Capability Simplifies Distributed Temperature-Sensing Applications
§ Requires No External Components
§ Can Be Powered from Data Line; Power Supply Range is 3.0V to 5.5V
§ Measures Temperatures from -55°C to +125°C (-67°F to +257°F)
§ ±0.5°C Accuracy from -10°C to +85°C
§ Thermometer Resolution is User Selectable from 9 to 12 Bits
§ Converts Temperature to 12-Bit Digital Word in 750ms (Max)

64-BIT LASERED ROM CODE   64位光刻ROM编码
Each DS18B20 contains a unique 64–bit code (see Figure 6) stored in ROM. The least significant 8 bits of the ROM code contain the DS18B20’s 1-Wire family code: 28h（8位家族编码）. The next 48 bits contain a unique serial number（48位序列码）. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from the first 56 bits of the ROM code（8位冗余检验码）. A detailed explanation of the CRC bits is provided in the CRC Generation section. The 64-bit ROM code and associated ROM function control logic allow the DS18B20 to operate as a 1-Wire device using the protocol detailed in the 1-Wire Bus System section.
Figure 6. 64-Bit Lasered ROM Code

示例程序

  1 #include <OneWire.h>
  2
  3
  4
  5 // OneWire DS18S20, DS18B20, DS1822 Temperature Example
  6
  7 //
  8
  9 // http://www.pjrc.com/teensy/td_libs_OneWire.html
 10
 11 //
 12
 13 // The DallasTemperature library can do all this work for you!
 14
 15 // http://milesburton.com/Dallas_Temperature_Control_Library
 16
 17
 18
 19 OneWire  ds(10);   // on pin 10，定义单总线设备ds，连接于10号引脚
 20
 21
 22
 23 void setup(void)
 24
 25 {
 26
 27   Serial.begin(9600);
 28
 29 }
 30
 31
 32
 33 void loop(void)
 34
 35 {
 36
 37   byte i;
 38
 39   byte present = 0;
 40
 41   byte type_s;
 42
 43   byte data[12];
 44
 45   byte addr[8];     //传感器的ROM，共8个字节的数据，64位
 46
 47   float celsius, fahrenheit;
 48
 49
 50
 51   if ( !ds.search(addr))    //查询不到ds就一直查询
 52
 53 {
 54
 55     Serial.println("No more addresses.");
 56
 57     Serial.println();
 58
 59     ds.reset_search();
 60
 61     delay(250);
 62
 63     return;
 64
 65   }
 66
 67
 68
 69   Serial.print("ROM =");    //查询到则显示ds的地址
 70
 71   for( i = 0; i < 8; i++)
 72
 73 {
 74
 75     Serial.write(' ');
 76
 77     Serial.print(addr[i], HEX);
 78
 79   }
 80
 81
 82
 83   if (OneWire::crc8(addr, 7) != addr[7])  // CRC检验失败的情况
 84
 85 {
 86
 87       Serial.println("CRC is not valid!");
 88
 89       return;
 90
 91   }
 92
 93   Serial.println();
 94
 95
 96
 97   // the first ROM byte indicates which chip ，根据addr[0]决定DS18系列的型号
 98
 99   switch (addr[0])
100
101 {
102
103     case 0x10:
104
105       Serial.println("  Chip = DS18S20");   // or old DS1820
106
107       type_s = 1;
108
109       break;
110
111     case 0x28:        //0x28是DS18B20的家族编码
112
113       Serial.println("  Chip = DS18B20");
114
115       type_s = 0;
116
117       break;
118
119     case 0x22:
120
121       Serial.println("  Chip = DS1822");
122
123       type_s = 0;
124
125       break;
126
127     default:
128
129       Serial.println("Device is not a DS18x20 family device.");
130
131       return;
132
133   }
134
135
136
137   ds.reset();   //复位
138
139   ds.select(addr);  // 选择设备
140
141   ds.write(0x44,1);
142
143  // start conversion, with parasite power on at the end，
144
145 //传感器内部温度变换保存在暂存器，0x44是传感器的协议编码
146
147
148
149   delay(1000);       // maybe 750ms is enough, maybe not
150
151   // we might do a ds.depower() here, but the reset will take care of it.
152
153
154
155   present = ds.reset();     //返回1表示有设备存在
156
157   ds.select(addr);
158
159   ds.read(0xBE);         // Read Scratchpad 读暂存器，0xBE是传感器的协议编码
160
161
162
163   Serial.print("  Data = ");
164
165   Serial.print(present,HEX);
166
167   Serial.print(" ");
168
169   for ( i = 0; i < 9; i++)
170
171 {           // we need 9 bytes
172
173     data[i] = ds.read();
174
175     Serial.print(data[i], HEX);
176
177     Serial.print(" ");
178
179   }
180
181   Serial.print(" CRC=");
182
183   Serial.print(OneWire::crc8(data, 8), HEX);
184
185   Serial.println();
186
187
188
189   // convert the data to actual temperature
190
191
192
193   unsigned int raw = (data[1] << 8) | data[0];
194
195   if (type_s)       //DS18S20对应的温度转换
196
197 {
198
199     raw = raw << 3;    // 9 bit resolution default
200
201    if (data[7] == 0x10)
202
203    {
204
205       // count remain gives full 12 bit resolution
206
207       raw = (raw & 0xFFF0) + 12 - data[6];
208
209     }
210
211   }
212
213 else      //DS18B20，DS1822对应的温度转换
214
215 {
216
217     byte cfg = (data[4] & 0x60);
218
219     if (cfg == 0x00) raw = raw << 3;    // 9 bit resolution, 93.75 ms
220
221     else if (cfg == 0x20) raw = raw << 2;   // 10 bit res, 187.5 ms
222
223     else if (cfg == 0x40) raw = raw << 1;   // 11 bit res, 375 ms
224
225     // default is 12 bit resolution, 750 ms conversion time
226
227   }
228
229   celsius = (float)raw / 16.0;    //摄氏温度
230
231   fahrenheit = celsius * 1.8 + 32.0;    //华氏温度
232
233   Serial.print("  Temperature = ");
234
235   Serial.print(celsius);
236
237   Serial.print(" Celsius, ");
238
239   Serial.print(fahrenheit);
240
241   Serial.println(" Fahrenheit");
242
243 }