89c51 ds1820 based digital thermometer

  
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The hardware configuration when using multiple 1-Wire temperature sensors like the DS1820 is very simple, as illustrated in the block diagram below. A single-wire bus is used for communication between the microcontroller and the temperature sensor. It is also possible to power the devices direclty via this 1-Wire bus. An almost unlimited number of
89c51 ds1820 based digital thermometer - schematic

1-WireTM devices can be connected to the bus because each device has a unique 64-bit ROM code identifier which is used to address each sensor Temperature measurement is one of the most common tasks performed by the microcontroller. A DS1820 sensor is used for measurement here. It is capable of measuring temperature in the range of -55 °C to 125 °C with 0. 5 °C accuracy. For the purpose of transferring data to the microcontroller, a special type of serial communication called 1-wire is used. Due to a simple and wide use of these sensors, commands used to run and control them are in the form of functions stored in the One_Wire library. There are three functions in total: Concretely, you don`t have to study documentation provided by the manufacturer in order to use this sensor. It is sufficient to copy some of these functions in the program. The OneWire library provides routines for communication via the Dallas OneWire protocol, e. g. with DS18x20 digital thermometer. OneWire is a Master/Slave protocol, and all communication cabling required is a single wire. OneWire enabled devices should have open collector drivers (with single pull-up resistor) on the shared data line. Each OneWire device has also a unique 64-bit registration number (8-bit device type, 48-bit serial number and 8-bit CRC), so multiple slaves can co-exist on the same bus.



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