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SHTSensor.h
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SHTSensor.h
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/*
* Copyright (c) 2018, Sensirion AG <[email protected]>
* Copyright (c) 2015-2016, Johannes Winkelmann <[email protected]>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the Sensirion AG nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SHTSENSOR_H
#define SHTSENSOR_H
#include <inttypes.h>
// Forward declaration
class SHTSensorDriver;
/**
* Official interface for Sensirion SHT Sensors
*/
class SHTSensor
{
public:
/**
* Enum of the supported Digital Sensirion SHT Sensors.
* For analog sensors, see SHT3xAnalogSensor.
* Using the special AUTO_DETECT sensor causes all i2c sensors to be
* probed. The first matching sensor will then be used.
*/
enum SHTSensorType {
/** Automatically detect the sensor type (only i2c sensors listed above) */
AUTO_DETECT,
// i2c Sensors:
/** SHT3x-DIS with ADDR (sensor pin 2) connected to VSS (default) */
SHT3X,
/** SHT3x-DIS with ADDR (sensor pin 2) connected to VDD */
SHT3X_ALT,
SHTC1,
SHTW1,
SHTW2
};
/**
* Accuracy setting of measurement.
* Not all sensors support changing the sampling accuracy.
*/
enum SHTAccuracy {
/** Highest repeatability at the cost of slower measurement */
SHT_ACCURACY_HIGH,
/** Balanced repeatability and speed of measurement */
SHT_ACCURACY_MEDIUM,
/** Fastest measurement but lowest repeatability */
SHT_ACCURACY_LOW
};
/** Value reported by getHumidity() when the sensor is not initialized */
static const float HUMIDITY_INVALID;
/** Value reported by getTemperature() when the sensor is not initialized */
static const float TEMPERATURE_INVALID;
/**
* Auto-detectable sensor types.
* Note that the SHTW1 and SHTW2 share exactly the same driver as the SHTC1
* and are thus not listed individually.
*/
static const SHTSensorType AUTO_DETECT_SENSORS[];
/**
* Instantiate a new SHTSensor
* By default, the i2c bus is queried for known SHT Sensors. To address
* a specific sensor, set the `sensorType'.
*/
SHTSensor(SHTSensorType sensorType = AUTO_DETECT)
: mSensorType(sensorType),
mSensor(NULL),
mTemperature(SHTSensor::TEMPERATURE_INVALID),
mHumidity(SHTSensor::HUMIDITY_INVALID)
{
}
virtual ~SHTSensor() {
cleanup();
}
/**
* Initialize the sensor driver
* To read out the sensor use readSample(), followed by getTemperature() and
* getHumidity() to retrieve the values from the sample
*/
bool init();
/**
* Read new values from the sensor
* After the call, use getTemperature() and getHumidity() to retrieve the
* values
* Returns true if the sample was read and the values are cached
*/
bool readSample();
/**
* Get the relative humidity in percent read from the last sample
* Use readSample() to trigger a new sensor reading
*/
float getHumidity() const {
return mHumidity;
}
/**
* Get the temperature in Celsius read from the last sample
* Use readSample() to trigger a new sensor reading
*/
float getTemperature() const {
return mTemperature;
}
/**
* Change the sensor accurancy, if supported by the sensor
* Returns true if the accuracy was changed
*/
bool setAccuracy(SHTAccuracy newAccuracy);
private:
void cleanup();
SHTSensorType mSensorType;
SHTSensorDriver *mSensor;
float mTemperature;
float mHumidity;
};
/** Abstract class for a digital SHT Sensor driver */
class SHTSensorDriver
{
public:
virtual ~SHTSensorDriver() = 0;
/**
* Set the sensor accuracy.
* Returns false if the sensor does not support changing the accuracy
*/
virtual bool setAccuracy(SHTSensor::SHTAccuracy newAccuracy) {
return false;
}
/** Returns true if the next sample was read and the values are cached */
virtual bool readSample();
/**
* Get the relative humidity in percent read from the last sample
* Use readSample() to trigger a new sensor reading
*/
float getHumidity() const {
return mHumidity;
}
/**
* Get the humidity in percent read from the last sample
* Use readSample() to trigger a new sensor reading
*/
float getTemperature() const {
return mTemperature;
}
float mTemperature;
float mHumidity;
};
/** Base class for i2c SHT Sensor drivers */
class SHTI2cSensor : public SHTSensorDriver {
public:
/** Size of i2c commands to send */
static const uint8_t CMD_SIZE;
/** Size of i2c replies to expect */
static const uint8_t EXPECTED_DATA_SIZE;
/**
* Constructor for i2c SHT Sensors
* Takes the `i2cAddress' to read, the `i2cCommand' issues when sampling
* the sensor and the values `a', `b', `c' to convert the fixed-point
* temperature value received by the sensor to a floating point value using
* the formula: temperature = a + b * (rawTemperature / c)
* and the values `x' and `y' to convert the fixed-point humidity value
* received by the sensor to a floating point value using the formula:
* humidity = x * (rawHumidity / y)
* duration is the duration in milliseconds of one measurement
*/
SHTI2cSensor(uint8_t i2cAddress, uint16_t i2cCommand, uint8_t duration,
float a, float b, float c,
float x, float y)
: mI2cAddress(i2cAddress), mI2cCommand(i2cCommand), mDuration(duration),
mA(a), mB(b), mC(c), mX(x), mY(y)
{
}
virtual ~SHTI2cSensor()
{
}
virtual bool readSample();
uint8_t mI2cAddress;
uint16_t mI2cCommand;
uint8_t mDuration;
float mA;
float mB;
float mC;
float mX;
float mY;
private:
static uint8_t crc8(const uint8_t *data, uint8_t len);
static bool readFromI2c(uint8_t i2cAddress,
const uint8_t *i2cCommand,
uint8_t commandLength, uint8_t *data,
uint8_t dataLength, uint8_t duration);
};
class SHT3xAnalogSensor
{
public:
/**
* Instantiate a new Sensirion SHT3x Analog sensor driver instance.
* The required paramters are `humidityPin` and `temperaturePin`
* An optional `readResolutionBits' can be set since the Arduino/Genuino Zero
* support 12bit precision analog readings. By default, 10 bit precision is
* used.
*
* Example usage:
* SHT3xAnalogSensor sht3xAnalog(HUMIDITY_PIN, TEMPERATURE_PIN);
* float humidity = sht.readHumidity();
* float temperature = sht.readTemperature();
*/
SHT3xAnalogSensor(uint8_t humidityPin, uint8_t temperaturePin,
uint8_t readResolutionBits = 10)
: mHumidityAdcPin(humidityPin), mTemperatureAdcPin(temperaturePin),
mReadResolutionBits(readResolutionBits)
{
}
virtual ~SHT3xAnalogSensor()
{
}
float readHumidity();
float readTemperature();
uint8_t mHumidityAdcPin;
uint8_t mTemperatureAdcPin;
uint8_t mReadResolutionBits;
};
#endif /* SHTSENSOR_H */