DS18B20：1-Wire数字温度传感器

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"DS18B20温度传感器是一种数字温度传感器，具备独特的1-Wire接口，仅需一个端口引脚即可进行通信，支持多设备挂载，简化了分布式温度测量应用的设计。该传感器无需外部组件，电源电压范围在3.0V到5.5V之间，且在待机时功耗为零。其工作温度范围广泛，可测量-55°C至+125°C的温度，精度在-10°C到+85°C范围内可达±0.5°C。传感器的分辨率可编程设置为9到12位，温度转换成数字信号的最长时间为750毫秒。此外，DS18B20还允许用户定义非易失性温度报警设置，当温度超出预设范围时，通过报警搜索命令可以识别并定位出问题的设备。这种传感器适用于恒温控制、工业系统、消费产品、温度计等各种对温度敏感的系统。" DS18B20温度传感器的主要特点包括： 1. **1-Wire接口**：这种独特的接口设计使得只需要一根数据线就能实现通信，极大地减少了硬件需求和布线复杂度。 2. **多滴模式**：允许多个DS18B20传感器连接到同一根总线上，方便构建分布式温度监测网络。 3. **无需外部组件**：传感器内部集成了所有必需的电路，简化了外围电路设计，降低了系统成本。 4. **电源管理**：传感器可以从数据线上获取电源，电压范围宽，适应性强，并且在不工作时不会消耗电力。 5. **宽温工作范围**：能够测量从-55°C到+125°C的温度，覆盖了大部分应用环境的需求。 6. **高精度**：在-10°C到+85°C的温度区间内，精度可达±0.5°C，确保了测量的准确性。 7. **可编程分辨率**：用户可以根据需要将温度转换的分辨率设置为9、10、11或12位，以平衡精度和处理速度。 8. **快速转换时间**：传感器能在750毫秒内完成12位温度数据的数字化转换，满足实时性要求。 9. **温度报警功能**：用户可以设置温度报警界限，当温度超出这些设定值时，传感器会触发报警，便于系统做出相应反应。 10. **PIN分配**：DS18B20有三个引脚，分别是GND（接地）、DQ（数据输入/输出）和VDD（电源电压），还有一个NC（无连接）引脚，不用于连接。 DS18B20因其紧凑的尺寸、高精度和易于集成的特性，在多种应用场景中得到广泛应用，如家庭自动化中的恒温器、工业过程控制、环境监测、医疗设备和各种消费电子产品等。

DS18B20

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64-BIT LASERED ROM

Each DS18B20 contains a unique ROM code that is 64-bits long. The first 8 bits are a 1-Wire family

code (DS18B20 code is 28h). The next 48 bits are a unique serial number. The last 8 bits are a CRC of

the first 56 bits. (See Figure 4.) The 64-bit ROM and ROM Function Control section allow the DS18B20

to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section “1-Wire Bus

System.” The functions required to control sections of the DS18B20 are not accessible until the ROM

function protocol has been satisfied. This protocol is described in the ROM function protocol flowchart

(Figure 5). The 1-Wire bus master must first provide one of five ROM function commands: 1) Read

ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM, or 5) Alarm Search. After a ROM function

sequence has been successfully executed, the functions specific to the DS18B20 are accessible and the

bus master may then provide one of the six memory and control function commands.

CRC GENERATION

The DS18B20 has an 8-bit CRC stored in the most significant byte of the 64-bit ROM. The bus master

can compute a CRC value from the first 56-bits of the 64-bit ROM and compare it to the value stored

within the DS18B20 to determine if the ROM data has been received error-free by the bus master. The

equivalent polynomial function of this CRC is:

CRC = X

+ X

+ 1

The DS18B20 also generates an 8-bit CRC value using the same polynomial function shown above and

provides this value to the bus master to validate the transfer of data bytes. In each case where a CRC is

used for data transfer validation, the bus master must calculate a CRC value using the polynomial

function given above and compare the calculated value to either the 8-bit CRC value stored in the 64-bit

ROM portion of the DS18B20 (for ROM reads) or the 8-bit CRC value computed within the DS18B20

(which is read as a ninth byte when the scratchpad is read). The comparison of CRC values and decision

to continue with an operation are determined entirely by the bus master. There is no circuitry inside the

DS18B20 that prevents a command sequence from proceeding if the CRC stored in or calculated by the

DS18B20 does not match the value generated by the bus master.

The 1-Wire CRC can be generated using a polynomial generator consisting of a shift register and XOR

gates as shown in Figure 6. Additional information about the Dallas 1-Wire Cyclic Redundancy Check is

available in Application Note 27 entitled “Understanding and Using Cyclic Redundancy Checks with

Dallas Semiconductor Touch Memory Products.”

The shift register bits are initialized to 0. Then starting with the least significant bit of the family code,

1 bit at a time is shifted in. After the 8th bit of the family code has been entered, then the serial number is

entered. After the 48

bit of the serial number has been entered, the shift register contains the CRC

value. Shifting in the 8 bits of CRC should return the shift register to all 0s.

64-BIT LASERED ROM Figure 4

8-BIT CRC CODE 48-BIT SERIAL NUMBER

8-BIT FAMILY CODE

(28h)

MSB LSB MSB LSB MSB LSB

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DS18B20：1-Wire数字温度传感器

DS18B20.C(一般通用的数字温度传感器)完成代码,可直接使用.

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