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208 lines
7.3 KiB
Markdown
208 lines
7.3 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/MCP9808_RT/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MCP9808_RT/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MCP9808_RT/issues)
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[](https://github.com/RobTillaart/MCP9808_RT/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MCP9808_RT/releases)
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[](https://registry.platformio.org/libraries/robtillaart/MCP9808)
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# MCP9808_RT
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Arduino library for I2C MCP9808 temperature sensor.
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## Description
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The MCP9808 is a temperature sensor that measures typically in 1/16th == 0.0625° Celsius.
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What makes this sensor interesting is the **ALERT** pin, which allows triggering of any piece
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of electronics if the temperature hits a predefined value or temperature zone.
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### MCP9808 breakout board
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```
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//
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// Adafruit MCP9808 breakout board
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// +----------+
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// |0 ALERT |---------------+--[ 4K7 ]---- +5V
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// | A2 |---- GND |
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// | A1 |---- GND +--[ LED ]---- GND // or other electronics.
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// | A0 |---- GND
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// | SDA |---- I2C MCU
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// | SCL |---- I2C MCU
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// | GND |---- GND MCU
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// |0 VCC |---- +5V
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// +----------+
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//
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// address above is 24
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//
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```
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## Interface
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```cpp
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#include "mcp9808.h"
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```
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#### Constructor
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- **MCP9808(const uint8_t address, TwoWire \*wire = &Wire)** Set the device address.
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Option one can set the I2C bus if multiple I2C buses are present.
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Default I2C bus is Wire.
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**0.4.0 Breaking change**
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The user must initialize the I2C bus in **setup()**, the library doesn't do that
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since 0.4.0. So one need to call **Wire.begin()** or **Wire.begin(SDA, SCL)**.
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#### Address
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There are max 8 sensors on one I2C bus.
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Normal address = 0011xxx where xxx = A2, A1, A0
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| Address | HEX | A2 | A1 | A0 |
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|:-------:|:------:|:----:|:----:|:----:|
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| 24 | 0x18 | 0 | 0 | 0 |
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| 25 | 0x19 | 0 | 0 | 1 |
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| 26 | 0x1A | 0 | 1 | 0 |
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| 27 | 0x1B | 0 | 1 | 1 |
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| 28 | 0x1C | 1 | 0 | 0 |
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| 29 | 0x1D | 1 | 0 | 1 |
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| 30 | 0x1E | 1 | 1 | 0 |
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| 31 | 0x1F | 1 | 1 | 1 |
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On request manufacturer will provide 1001xxx as base address
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allowing up to 16 temp sensors on one bus.
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#### Temperature and status
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- **void setOffset(float offset = 0.0)** set an offset to calibrate or to correct for self heating.
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The value of offset is not validated to keep footprint small.
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- **float getOffset()** return value of offset (default 0).
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- **float getTemperature()** read the ambient temperature.
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- **uint8_t getStatus()** returns the status bits of the last call to **getTemperature()**
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The value returned by **getStatus()** is the last value read by the call to **GetTemperature()**.
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There are three bits, see table below.
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A value of 6 == mask == 110 means that TA is above the upper AND above the critical temperature.
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| Bit | Mask | Description | Notes |
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|:-----:|:------:|:--------------|:-----------------|
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| 0 | 0x01 | TA < TLOWER | lower |
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| 1 | 0x02 | TA > TUPPER | larger |
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| 2 | 0x04 | TA ≥ TCRIT | larger or equal |
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#### Resolution
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- **void setResolution(uint8_t resolution = 3)** set the resolution, if resolution > 3, it is not set.
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- **uint8_t getResolution()** returns the resolution set.
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| Value | Resolution | Conversion | Samples/s | Notes |
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|:-------:|:-------------|:------------:|:-----------:|:--------:|
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| 0 | 0.5°C | 30 ms | 33 | |
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| 1 | 0.25°C | 65 ms | 15 | |
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| 2 | 0.125°C | 130 ms | 7 | |
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| 3 | 0.0625°C | 250 ms | 4 | default |
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Note: for the same resolution the MCP9808 is about 3x faster than
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the popular DS18B20.
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#### Configuration
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- **void setConfigRegister(uint16_t configuration)** see table below + read datasheet.
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- **uint16_t getConfigRegister()** return set value.
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| Bit | Mask | Name | Description | Value |
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|:-----:|:------:|:-----------|:----------------|:-------|
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| 0 | 0x0001 | ALT MOD | alert mode | **0 = comparator output**, 1 = interrupt output
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| 1 | 0x0002 | ALT POL | alert polarity | **0 = active low**, 1 = active high
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| 2 | 0x0004 | ALT SEL | alert select | **0 = upper+lower+crit**, 1 = critical only
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| 3 | 0x0008 | ALT CNT | alert control | **0 = OFF**, 1 = ON
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| 4 | 0x0010 | ALT STAT | alert status | **0 = OFF**, 1 = ON (read!)
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| 5 | 0x0020 | INT CLR | interrupt clear | **0 = none**, 1 = clear interrupt
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| 6 | 0x0040 | WIN LOC | lock Tup + Tlow | **0 = unlocked**, 1 = Lock
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| 7 | 0x0080 | CRT LOC | lock Tcritical | **0 = unlocked**, 1 = Lock
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| 8 | 0x0100 | SHDN | shutdown, | **0 = continuous mode**, 1 = low power
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| 9-10 | 0x0600 | Hysteresis | Thysteresis | **00 = 0°C**, 01 = 1.5°C, 10 = 3°C, 11 = 6°C
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| 11-15 | | always 0 | |
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Check datasheet for the details...
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#### Temperature limits / thresholds
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- **void setTupper(float temp)** write upper register, accuracy 0.25°C.
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- **float getTupper()** idem.
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- **void setTlower(float temp)** write lower register, accuracy 0.25°C.
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- **float getTlower()** idem.
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- **void setTcritical(float temp)** write critical register, accuracy 0.25°C.
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- **float getTcritical()** idem.
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The values written in these registers, are the trigger values for the status
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read with getStatus. Note that the Hysteresis temperature delta affects the
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value of these triggers.
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The values set are not validated to keep footprint of the library small.
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#### Miscellaneous
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- **uint16_t getManufacturerID()** returns 84 (my version).
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- **uint8_t getDeviceID()** returns 0 (my version).
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- **uint8_t getRevision()** returns 84 (my version).
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- **uint16_t getRFU()** returns 29 (my version). Reserved for future use.
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#### Hidden registers
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The MCP9808 has hidden registers mentioned only on p.16 of the datasheet.
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These are for testing and calibration.
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The library prevents reading / writing them to keep sensors working.
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## Future
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#### Must
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- refactor the constructor to include Wire param
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- add begin() function.
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#### Should
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- update documentation
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- compare DS18B20?
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- test more
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- negative temperatures
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- do unit test
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- check for optimizations
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#### Could
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- add examples
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- for the **ALERT**
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- multi sensor
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#### Wont
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## Support
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If you appreciate my libraries, you can support the development and maintenance.
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Improve the quality of the libraries by providing issues and Pull Requests, or
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donate through PayPal or GitHub sponsors.
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Thank you,
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