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165 lines
5.5 KiB
Markdown
165 lines
5.5 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/DS18B20_INT/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/DS18B20_INT/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/DS18B20_INT/blob/master/LICENSE)
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[](https://github.com/RobTillaart/DS18B20_INT/releases)
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# DS18B20_INT
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Minimalistic library for the DS18B20 temperature sensor - restricted to one sensor per pin.
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## Arduino Temperature Control Library (ATCL)
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This DS18B20 library is a minimalistic library for a DS18B20 sensor.
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It will give only temperatures in whole degrees C.
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Goal is to minimize footprint.
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If you need more functions or control over the DS18B20 family I refer to the library
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of Miles Burton - https://github.com/milesburton/Arduino-Temperature-Control-Library
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I'm a great fan of the above library however some time ago I needed to strip it down
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to save a few dozen bytes. I reworked that minimalistic version into a library and I
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added a number of Arduino examples to help you get started.
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#### Related
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This library is related to
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- https://github.com/RobTillaart/DS18B20_INT
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- https://github.com/RobTillaart/DS18B20_RT
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- https://github.com/milesburton/Arduino-Temperature-Control-Library
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## Interface
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```cpp
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#include "DS18B20_INT.h"
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```
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#### Core
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This DS18B20_INT library supports only the DS18B20, only one sensor per pin, no parasite
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mode, no Fahrenheit and no alarm functions. The only feature the class supports is
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the asynchronous reading of the temperature by means of three core functions:
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- **DS18B20_INT(OneWire \*)** constructor needs a reference to OneWire object.
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- **bool begin(uint8_t retries = 3)** resets oneWire and set resolution default to 9 bit.
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Returns true if address / device is found and all is OK.
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There will be a number of retries to connect, default 3.
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- **bool isConnected()** Returns true if address / device is found.
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- **void requestTemperatures()** trigger temperature conversion.
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- **bool isConversionComplete()** check if conversion is complete.
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- **int16_t getTempC()** returns temperature in whole degrees only. -55..125
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or -127 = DEVICE_DISCONNECTED
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- **bool getAddress()** returns true if the sensor is configured (available).
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#### CentiC part
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The following functions are experimental since 0.2.0
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They allow to use a higher resolution while not using floats.
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This keeps the library small.
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- **bool setResolution(uint8_t bits = 9)** sets the internal resolution to 9, 10, 11 or 12 bits.
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Other numbers will be mapped on 9.
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This will affect the conversion time for a measurement.
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Internally it will call **begin()** to set the new resolution.
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Returns false if no address / device can be found.
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- **void getResolution()** returns the bits set, default 9.
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Convenience function.
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- **getTempCentiC(void)** returns the measured temperature times 100. -5500..12500
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So 10.62°C will be returned as 1062.
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Note one might need to set the resolution.
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**Warning** The DEVICE_DISCONNECTED is not tested for, but is commented in the code.
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Use at own risk.
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## Operation
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This library supports only one DS18B20 per Arduino/ MCU pin.
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```
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// BOTTOM VIEW
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//
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// PIN MEANING
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// /---+
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// / o | 1 GND
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// | o | 2 DATA
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// \ o | 3 VCC
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// \---+
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```
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(always check datasheet)
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Connect a pull-up resistor 4.7 KOhm between pin3 and pin2.
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When the wires are longer this resistor needs to be smaller.
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#### Pull up resistor
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An **indicative** table for pull up resistors, (E12 series), to get started.
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Note: thicker wires require smaller resistors (typically 1 step in E12 series)
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| Length | 5.0 Volt | 3.3 Volt | Notes |
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|----------------:|------------:|-----------:|:--------|
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| 10cm (4") | 10K0 | 6K8 | might work without |
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| 20cm (8") | 8K2 | 4K7 |
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| 50cm (20") | 4K7 | 3K3 |
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| 100cm (3'4") | 3K3 | 2K2 |
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| 200cm (6'8") | 2K2 | 1K0 |
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| 500cm (16'8") | 1K0 | \* |
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| longer | \* | \* |
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\* = no info, smaller?
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## Performance
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To elaborate connected state.
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Tested on UNO, 16 MHz, time in microseconds.
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Measured with DS18B20_performance.ino
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| function | not connected | connected |
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|:-----------------------|:---------------:|:-----------:|
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| begin | 920 | - |
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| getAddress | 4 | - |
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| requestTemperatures | 1276 | - |
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| isConversionComplete | 72 | - |
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| getTempC | 912 | - |
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## Credits
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Miles Burton who originally developed the Arduino Temperature Control Library.
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and all people who contributed to that lib.
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## Future
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#### Must
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- elaborate performance connected state.
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#### Should
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- add examples
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- a multi sensor == multiple pins, no bus
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#### Could
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- add rounding for **getTempC()**.
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- now it truncates, so it can be 0.5°C off.
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- add "0.5" to raw and truncate improves only for 10 bits and higher.
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#### Wont
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- unit tests
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- get it working
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