Penn Electric / LinearAnalogSensors

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.cpp@2:989048937c77, 2012-12-23 (annotated)

Committer:
PennElectric
Date:
Sun Dec 23 07:32:24 2012 +0000
Revision:
2:989048937c77
Parent:
0:d84ef842074b 
Fixed operator shorthand

Who changed what in which revision?

UserRevisionLine numberNew contents of line
PennElectric 0:d84ef842074b 1 /* Copyright (c) <2012> <P. Patel>, MIT License
PennElectric 0:d84ef842074b 2 *
PennElectric 0:d84ef842074b 3 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
PennElectric 0:d84ef842074b 4 * and associated documentation files (the "Software"), to deal in the Software without restriction,
PennElectric 0:d84ef842074b 5 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
PennElectric 0:d84ef842074b 6 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
PennElectric 0:d84ef842074b 7 * furnished to do so, subject to the following conditions:
PennElectric 0:d84ef842074b 8 *
PennElectric 0:d84ef842074b 9 * The above copyright notice and this permission notice shall be included in all copies or
PennElectric 0:d84ef842074b 10 * substantial portions of the Software.
PennElectric 0:d84ef842074b 11 *
PennElectric 0:d84ef842074b 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
PennElectric 0:d84ef842074b 13 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
PennElectric 0:d84ef842074b 14 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
PennElectric 0:d84ef842074b 15 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
PennElectric 0:d84ef842074b 16 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
PennElectric 0:d84ef842074b 17 */
PennElectric 0:d84ef842074b 18
PennElectric 0:d84ef842074b 19 // --------------------- Median Filtered Linear Temperature Sensor Reader ----------------------------
PennElectric 0:d84ef842074b 20
PennElectric 0:d84ef842074b 21 #include "LinearTemp.h"
PennElectric 0:d84ef842074b 22 #include "mbed.h"
PennElectric 0:d84ef842074b 23
PennElectric 0:d84ef842074b 24 // Constructor using two calibration points to define linear multiplier and offset
PennElectric 0:d84ef842074b 25 LinearTemp::LinearTemp(PinName pin, float temp1, unsigned short read1, float temp2, unsigned short read2):_pin(pin) {
PennElectric 0:d84ef842074b 26 _temp = 0.0; // Zero the temperature
PennElectric 0:d84ef842074b 27 _multiplier = (temp2 - temp1) / (read2 - read1); // Calculate multiplier as slope
PennElectric 0:d84ef842074b 28 _offset = temp1 - (_multiplier * read1); // Calculate offset
PennElectric 0:d84ef842074b 29 }
PennElectric 0:d84ef842074b 30 // Constructor using user defined multiplier and offset
PennElectric 0:d84ef842074b 31 LinearTemp::LinearTemp(PinName pin, float multiplier, float offset):_pin(pin) {
PennElectric 0:d84ef842074b 32 _temp = 0.0; // Zero the temperature
PennElectric 0:d84ef842074b 33 _multiplier = multiplier; // Set multiplier
PennElectric 0:d84ef842074b 34 _offset = offset; // Set offset
PennElectric 0:d84ef842074b 35 }
PennElectric 0:d84ef842074b 36
PennElectric 0:d84ef842074b 37 // Populates an array with temperature readings, sorts, and returns median
PennElectric 0:d84ef842074b 38 float LinearTemp::readTemp() {
PennElectric 0:d84ef842074b 39 _tempArr[0] = _pin.read_u16();
PennElectric 0:d84ef842074b 40 for (int i = 1; i < 9; i++) {
PennElectric 0:d84ef842074b 41 _tempArr[i] = _pin.read_u16();
PennElectric 0:d84ef842074b 42 unsigned short tmp = _tempArr[i];
PennElectric 0:d84ef842074b 43 int j;
PennElectric 0:d84ef842074b 44 for (j = i - 1; j >= 0; j--) {
PennElectric 0:d84ef842074b 45 if (tmp>=_tempArr[j]) break;
PennElectric 0:d84ef842074b 46 _tempArr[j + 1] = _tempArr[j];
PennElectric 0:d84ef842074b 47 }
PennElectric 0:d84ef842074b 48 _tempArr[j + 1] = tmp;
PennElectric 0:d84ef842074b 49 }
PennElectric 0:d84ef842074b 50 _temp = (_tempArr[4] * _multiplier) + _offset;
PennElectric 0:d84ef842074b 51 return _temp;
PennElectric 0:d84ef842074b 52 }
PennElectric 0:d84ef842074b 53 // Returns last calculated temperature value
PennElectric 0:d84ef842074b 54 float LinearTemp::getTemp() {
PennElectric 0:d84ef842074b 55 return _temp;
PennElectric 0:d84ef842074b 56 }