This library is designed to work with devices like the LM335 temperature sensor. There are only two requirements for compatibility: 1) The device must be a sensor device that has an analog voltage output. 2) The physical quantity measured must vary linearly with the analog voltage. The LM335 creates an analog voltage proportional to temperature. It can work very well with this library using the nominal multiplier of 0.0050354 and offset of -273.15 or by providing two user defined calibration points to the constructor. It uses a median filter to remove unwanted noise from ADC readings.
Dependents: mbed_measuring_temperature
LinearTemp.h
- Committer:
- PennElectric
- Date:
- 2012-12-23
- Revision:
- 2:989048937c77
- Parent:
- 1:7ce89c2ecf05
File content as of revision 2:989048937c77:
/* Copyright (c) <2012> <P. Patel>, MIT License * * Permission is hereby granted, free of charge, to any person obtaining a copy of this software * and associated documentation files (the "Software"), to deal in the Software without restriction, * including without limitation the rights to use, copy, modify, merge, publish, distribute, * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all copies or * substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ // --------------------- Median Filtered Linear Temperature Sensor Reader ------------------------ #ifndef LINEAR_TEMP #define LINEAR_TEMP #include "mbed.h" /** This library is designed to work with devices like the LM335 temperature sensor. There are only * two requirements for compatibility of a device with this library: 1) It must be a sensor device * that has an analog voltage output. 2) The physical quantity measured must vary linearly with * the analog voltage. The LM335 which creates an analog voltage proportional to temperature * can work very well with this library using the nominal multiplier of 0.0050354 and offset of * -273.15 or by providing two calibration points to the constuctor to generate a linear response. It * samples the sensor 9 times and uses the median to minimize the effect of poor ADC readings and sudden * changes. * * Example: * @code * LinearTemp mysensor(p20, 0.0050354, -273.15); // Setup a LM335 temp sensor on pin 20 * DigitalOut myled(LED1); * * int main() { * while(1) { * // Light LED if filtered temperature is greater than 45 degrees Celsius * if (mysensor > 45) myled = 1; * else myled = 0; * } * } * @endcode */ class LinearTemp { public: /** Create a calibrated temperature sensor object connected to an Analog input pin * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected * @param temp1 Temperature (float in degrees C or F) of first calibration point * @param read1 Mbed ADC reading (unsigned short) of first calibration point * @param temp2 Temperature (float in degrees C or F) of second calibration point * @param read2 Mbed ADC reading (unsigned short) of second calibration point */ LinearTemp(PinName pin, float temp1, unsigned short read1, float temp2, unsigned short read2); /** Create a calibrated temperature sensor object connected to an Analog input pin * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected * @param multiplier Conversion multiplier to go from ADC reading as unsigned short to temperature (change in degrees / change in unsigned short) * @param offset Conversion offset (positive or negative) */ LinearTemp(PinName pin, float multiplier, float offset); /** Returns a new median-filtered, converted reading from the sensor * @returns New temperature (float) in degrees C or F as designated by the calibration points */ float readTemp(); /** Return the last calculated and stored temperature * @returns Last stored temperature (float) in degrees C or F as designated by the calibration points */ float getTemp(); #ifdef MBED_OPERATORS /** An operator shorthand for readTemp() to calculate filtered temperature */ operator float() { return readTemp(); } #endif private: AnalogIn _pin; unsigned short _tempArr[9]; float _temp; float _multiplier; float _offset; }; #endif