外文翻譯---一種基于ds18b20的溫度探測系統(tǒng)-文庫吧
2025-01-03 14:58 本頁面
【正文】 cific 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.3. APPLICATION THE GROUPING TEST METHODThis 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 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 sensors on 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.Fig 2 DS18B20 grouping sketch mapNow 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 above 60us。 the span of writing or reading the next bit is 1us. As the A/D conversion time is (9 precisions), if it is counted by the shortest way, the total timeconsuming of alternate test is calculated respectivel
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