DS18B20数字温度传感器详细中文指南

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"18B20是一款由Dallas Semiconductor（现Maxim Integrated）生产的数字温度传感器，具有独特的1-Wire接口，适用于各种分布式温度感应应用。这款传感器无需外部组件，可直接从数据线获取电源，工作电压范围为3.0V至5.5V，并且在待机时几乎不消耗电能。它能在-55°C到+125°C的温度范围内进行测量，精度在-10°C到+85°C时可达±0.5°C。传感器的分辨率可通过编程设置为9到12位，转换12位温度数据至数字信号最快只需750毫秒。此外，DS18B20还支持用户定义的非易失性温度报警设置，当温度超出预设范围时，可通过Alarm Search命令快速定位出故障设备。这款传感器广泛应用于恒温控制系统、工业系统、消费产品、温度计以及任何对温度敏感的系统中。其引脚分配包括GND（接地）、DQ（数据输入/输出）和VDD（电源电压），而NC（无连接）表示该引脚未使用。" 18B20的核心特性： 1. **1-Wire接口**：18B20的独特之处在于它只需要一根数据线就能实现通信，大大简化了布线和硬件设计。 2. **多滴能力**：支持多设备串联，可以构建分布式温度监测网络。 3. **无需外部组件**：传感器内置所需电路，降低了系统的复杂性。 4. **电源管理**：可以从数据线上获取电源，电压范围宽，同时在待机状态下几乎不消耗电能。 5. **宽温度范围**：工作温度范围广，从-55°C到+125°C，覆盖了许多应用场合。 6. **高精度**：在特定温度区间内提供±0.5°C的精度，确保了测量的准确性。 7. **可编程分辨率**：用户可以根据需求调整温度读数的分辨率，范围从9到12位。 8. **快速转换**：转换12位温度数据至数字值的时间最快为750毫秒，响应速度快。 9. **温度报警功能**：支持设定非易失性的温度报警点，一旦超过设定范围，能快速识别并处理。 10. **应用广泛**：适用于多种环境，如恒温器、工业控制系统、消费电子产品等。在实际应用中，DS18B20的使用需要配合微控制器或计算机，通过1-Wire协议进行通信，读取和设置传感器的各项参数。开发人员可以利用各种库和驱动程序来简化与18B20的交互，例如在Arduino平台上有许多现成的库供开发者使用。在设计系统时，应考虑如何有效地供电（如使用数据线供电或外部电源），以及如何妥善处理信号的传输和干扰问题，以确保稳定可靠的温度数据获取。

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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