基于ds18b20分组方式测温系统设计外文翻译(编辑修改稿)

基于ds18b20分组方式测温系统设计外文翻译(编辑修改稿)内容摘要：

统设计 10 which influences the efficiency of the multipoint temperature test system seriously. In this paper, DS18B20 are hung on some I/O buses by grouping DS18B20 evenly, and the conversion temperature data is obtained by reading the state of DS18B20, then the system loss decreases and the alternate test speed increases obviously, which won’t influence the precision and the reliability of the conversion. A set of multipoint temperature test of artificial environment laboratory is achieved in this paper, which increases the test efficiency of the former system. Ⅱ . CHARACTERISTICS OF DS18B20 DS18B20 is the single bus digital temperature sensor from American Dallas Company. DS18B20 is consisted of the 64 figures ROM engraved by laser, the temperature sensitivity ponent, nonvolatile temperature alarms trigger (Device TH and TL).DS18B20 municates with the microprocessor by the single bus port and the test range of DS18B20 is from 55 centigrade to +125 centigrade, and the incremental value is centigrade. The temperature can be changed into figures within 720ms and each DS18B20 has the sole 64 figures serial number. The specific content is revealed as Fig 1: There are two 8 figures storages ( and ) for storing temperature value in DS18B20. storage stores plement of the temperature value, and stores symbols of the temperature value. The user can define nonvolatile temperature alarms sets and distinguish the alarms search order and seek the ponent temperature alarms state outside the scheduled limit. There are two alternative ways of power supply: Signal bus highlevel borrow power is adopted, or the +5v power supply externally is adopted directly. Fig 1 DS18B20 64bit ROM Ⅲ . APPLICATION THE GROUPING TEST METHOD This paper illustrates the grouping method with the interface of DS18B20 and 89C52. Assuming the amount of the buses on P1 port is 4 and the temperature test 基于 DS18B20 分组方式测温系统设计 11 system needs 100 DS18B20 sensors, which can be distributed equally to the 4 I/O lines. If the number of sensors cannot be divided by the number of buses even, the number disparity of sensorson buses is no more than one, which can be handled while reading numbers. The power is supplied externally. Owning to the synchronistic conversion in each DS18B20, the intense current is needed, and the signal bus cannot be used for the power supply, otherwise the system cannot work in order. The schematic circuit is shown as Fig 2 (the DS18B20 signal buses of the same group are hung on some buses of P1 port). When read and write the DS18B20, the strict schedule must be kept. First a reversion pulse is sent to all DS18B20. After the reversion, Skip ROM order is sent to each circuit simultaneously from the I/O port, and the conversion order is sent, then all sensors begin transform. After the conversion, Match Rom order is sent to each circuit simultaneously, and 64 bits serial number is sent. DS18B20 is selected for each group, and Scratch Pad data is read. Finally the data is transformed. The data of serialread is transformed into the actual temperature value. One alternate test is finished after the DS18B20 temperature data is read pletely by the cyclical reading for 25 times. The whole flow chart is shown as Fig 3. Now the timeconsuming in the test system of the single bus and the grouping analyses method is illustrated respectively. The reversion time sequence and the time sequence of writing and reading one bit for the microprocessor are revealed in figures 46. The figure show: The reversion period of DS18B20 is 495us1020us。 the writing period of one bit is 60us120us。 the reading period of one bit is。