Penn Electric / LinearAnalogSensor

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. It uses a median filter to remove unwanted noise from ADC readings. The number of samples in the filter can be specified as an argument, as well as calibration points or a linear multiplier and coefficient.

LinearAnalogSensor.h@0:78eeca1c1944, 2013-08-07 (annotated)

Committer:
PennElectric
Date:
Wed Aug 07 19:37:12 2013 +0000
Revision:
0:78eeca1c1944
Recent update with the names changed and variable number of samples.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
PennElectric 0:78eeca1c1944 1 /* Copyright (c) <2012> <P. Patel>, MIT License
PennElectric 0:78eeca1c1944 2 *
PennElectric 0:78eeca1c1944 3 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
PennElectric 0:78eeca1c1944 4 * and associated documentation files (the "Software"), to deal in the Software without restriction,
PennElectric 0:78eeca1c1944 5 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
PennElectric 0:78eeca1c1944 6 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
PennElectric 0:78eeca1c1944 7 * furnished to do so, subject to the following conditions:
PennElectric 0:78eeca1c1944 8 *
PennElectric 0:78eeca1c1944 9 * The above copyright notice and this permission notice shall be included in all copies or
PennElectric 0:78eeca1c1944 10 * substantial portions of the Software.
PennElectric 0:78eeca1c1944 11 *
PennElectric 0:78eeca1c1944 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
PennElectric 0:78eeca1c1944 13 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
PennElectric 0:78eeca1c1944 14 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
PennElectric 0:78eeca1c1944 15 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
PennElectric 0:78eeca1c1944 16 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
PennElectric 0:78eeca1c1944 17 */
PennElectric 0:78eeca1c1944 18
PennElectric 0:78eeca1c1944 19 // --------------------- Median Filtered Linear Temperature Sensor Reader ------------------------
PennElectric 0:78eeca1c1944 20
PennElectric 0:78eeca1c1944 21 #ifndef LINEAR_ANALOG
PennElectric 0:78eeca1c1944 22 #define LINEAR_ANALOG
PennElectric 0:78eeca1c1944 23
PennElectric 0:78eeca1c1944 24 #include "mbed.h"
PennElectric 0:78eeca1c1944 25 /** This library is designed to work with devices like the LM335 temperature sensor. There are only
PennElectric 0:78eeca1c1944 26 * two requirements for compatibility of a device with this library: 1) It must be a sensor device
PennElectric 0:78eeca1c1944 27 * that has an analog voltage output. 2) The physical quantity measured must vary linearly with
PennElectric 0:78eeca1c1944 28 * the analog voltage. The LM335 which creates an analog voltage proportional to temperature
PennElectric 0:78eeca1c1944 29 * can work very well with this library using the nominal multiplier of 0.0050354 and offset of
PennElectric 0:78eeca1c1944 30 * -273.15 or by providing two calibration points to the constuctor to generate a linear response. It
PennElectric 0:78eeca1c1944 31 * samples the sensor 9 times and uses the median to minimize the effect of poor ADC readings and sudden
PennElectric 0:78eeca1c1944 32 * changes.
PennElectric 0:78eeca1c1944 33 *
PennElectric 0:78eeca1c1944 34 * Example:
PennElectric 0:78eeca1c1944 35 * @code
PennElectric 0:78eeca1c1944 36 * LinearAnalogSensor mysensor(p20, 0.0050354, -273.15); // Setup a LM335 temp sensor on pin 20
PennElectric 0:78eeca1c1944 37 * DigitalOut myled(LED1);
PennElectric 0:78eeca1c1944 38 *
PennElectric 0:78eeca1c1944 39 * int main() {
PennElectric 0:78eeca1c1944 40 * while(1) {
PennElectric 0:78eeca1c1944 41 * // Light LED if filtered temperature is greater than 45 degrees Celsius
PennElectric 0:78eeca1c1944 42 * if (mysensor > 45) myled = 1;
PennElectric 0:78eeca1c1944 43 * else myled = 0;
PennElectric 0:78eeca1c1944 44 * }
PennElectric 0:78eeca1c1944 45 * }
PennElectric 0:78eeca1c1944 46 * @endcode
PennElectric 0:78eeca1c1944 47 */
PennElectric 0:78eeca1c1944 48 class LinearAnalogSensor {
PennElectric 0:78eeca1c1944 49 public:
PennElectric 0:78eeca1c1944 50 /** Create a calibrated temperature sensor object connected to an Analog input pin
PennElectric 0:78eeca1c1944 51 * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected
PennElectric 0:78eeca1c1944 52 * @param numSamples Number of samples over which to apply a median filter
PennElectric 0:78eeca1c1944 53 * @param temp1 Temperature (float in degrees C or F) of first calibration point
PennElectric 0:78eeca1c1944 54 * @param read1 Mbed ADC reading (unsigned short) of first calibration point
PennElectric 0:78eeca1c1944 55 * @param temp2 Temperature (float in degrees C or F) of second calibration point
PennElectric 0:78eeca1c1944 56 * @param read2 Mbed ADC reading (unsigned short) of second calibration point
PennElectric 0:78eeca1c1944 57 */
PennElectric 0:78eeca1c1944 58 LinearAnalogSensor(PinName pin, int numSamples, float temp1, unsigned short read1, float temp2, unsigned short read2);
PennElectric 0:78eeca1c1944 59 /** Create a calibrated temperature sensor object connected to an Analog input pin
PennElectric 0:78eeca1c1944 60 * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected
PennElectric 0:78eeca1c1944 61 * @param numSamples Number of samples over which to apply a median filter
PennElectric 0:78eeca1c1944 62 * @param multiplier Conversion multiplier to go from ADC reading as unsigned short to temperature (change in degrees / change in unsigned short)
PennElectric 0:78eeca1c1944 63 * @param offset Conversion offset (positive or negative)
PennElectric 0:78eeca1c1944 64 */
PennElectric 0:78eeca1c1944 65 LinearAnalogSensor(PinName pin, int numSamples, float multiplier, float offset);
PennElectric 0:78eeca1c1944 66 /** Returns a new median-filtered, converted reading from the sensor
PennElectric 0:78eeca1c1944 67 * @returns New temperature (float) in degrees C or F as designated by the calibration points
PennElectric 0:78eeca1c1944 68 */
PennElectric 0:78eeca1c1944 69 float read();
PennElectric 0:78eeca1c1944 70 /** Return the last calculated and stored temperature
PennElectric 0:78eeca1c1944 71 * @returns Last stored temperature (float) in degrees C or F as designated by the calibration points
PennElectric 0:78eeca1c1944 72 */
PennElectric 0:78eeca1c1944 73 float getLast();
PennElectric 0:78eeca1c1944 74 #ifdef MBED_OPERATORS
PennElectric 0:78eeca1c1944 75 /** An operator shorthand for readTemp() to calculate filtered temperature
PennElectric 0:78eeca1c1944 76 */
PennElectric 0:78eeca1c1944 77 operator float() {
PennElectric 0:78eeca1c1944 78 return read();
PennElectric 0:78eeca1c1944 79 }
PennElectric 0:78eeca1c1944 80 #endif
PennElectric 0:78eeca1c1944 81 private:
PennElectric 0:78eeca1c1944 82 AnalogIn _pin;
PennElectric 0:78eeca1c1944 83 unsigned short * _arr;
PennElectric 0:78eeca1c1944 84 float _reading;
PennElectric 0:78eeca1c1944 85 float _multiplier;
PennElectric 0:78eeca1c1944 86 int _numSamples;
PennElectric 0:78eeca1c1944 87 float _offset;
PennElectric 0:78eeca1c1944 88 };
PennElectric 0:78eeca1c1944 89 #endif