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
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 }