Revision 0:78eeca1c1944, committed 2013-08-07

Comitter:

PennElectric

Date:

Wed Aug 07 19:37:12 2013 +0000

Commit message:

Recent update with the names changed and variable number of samples.

Changed in this revision

diff -r 000000000000 -r 78eeca1c1944 LinearAnalogSensor.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/LinearAnalogSensor.cpp	Wed Aug 07 19:37:12 2013 +0000
@@ -0,0 +1,66 @@
+/* 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 ----------------------------
+ 
+#include "LinearAnalogSensor.h"
+#include "mbed.h"
+
+// Constructor using two calibration points to define linear multiplier and offset
+LinearAnalogSensor::LinearAnalogSensor(PinName pin, int numSamples, float temp1, unsigned short read1, float temp2, unsigned short read2):_pin(pin) {
+    _reading = 0.0;                                     // Zero the temperature
+    _multiplier = (temp2 - temp1) / (read2 - read1); // Calculate multiplier as slope
+    _offset = temp1 - (_multiplier * read1);         // Calculate offset
+    _numSamples = numSamples;
+    _arr = new unsigned short[numSamples];
+}
+// Constructor using user defined multiplier and offset
+LinearAnalogSensor::LinearAnalogSensor(PinName pin, int numSamples, float multiplier, float offset):_pin(pin) {
+    _reading = 0.0;                                     // Zero the temperature
+    _multiplier = multiplier;                        // Set multiplier
+    _offset = offset;                                // Set offset
+    _numSamples = numSamples;
+    _arr = new unsigned short[numSamples];
+}
+
+// Populates an array with temperature readings, sorts, and returns median
+float LinearAnalogSensor::read() {
+    memset(_arr, 0, _numSamples * sizeof(unsigned short));
+    _arr[0] = _pin.read_u16();
+    for (int i = 1; i < _numSamples; i++) { 
+        _arr[i] = _pin.read_u16();
+        unsigned short tmp = _arr[i];
+        int j;            
+        for (j = i - 1; j >= 0; j--) {
+            if (tmp>=_arr[j]) break;
+            _arr[j + 1] = _arr[j];
+        }
+        _arr[j + 1] = tmp;
+    }
+    if (_numSamples % 2 == 0) {
+        _reading = (((_arr[_numSamples >> 1] + _arr[(_numSamples >> 1) - 1]) / (2.0)) * _multiplier) + _offset;
+    }
+    if (_numSamples % 2 == 1)  {
+        _reading = (_arr[_numSamples >> 1] * _multiplier) + _offset;
+    }
+    return _reading;
+}
+// Returns last calculated temperature value
+float LinearAnalogSensor::getLast() {
+    return _reading;
+}
\ No newline at end of file

diff -r 000000000000 -r 78eeca1c1944 LinearAnalogSensor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/LinearAnalogSensor.h	Wed Aug 07 19:37:12 2013 +0000
@@ -0,0 +1,89 @@
+/* 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_ANALOG
+#define LINEAR_ANALOG
+
+#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
+ * LinearAnalogSensor 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 LinearAnalogSensor {
+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 numSamples Number of samples over which to apply a median filter
+     * @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
+     */
+    LinearAnalogSensor(PinName pin, int numSamples, 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 numSamples Number of samples over which to apply a median filter
+     * @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)
+     */
+    LinearAnalogSensor(PinName pin, int numSamples, 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 read();
+    /** Return the last calculated and stored temperature
+      * @returns Last stored temperature (float) in degrees C or F as designated by the calibration points
+      */
+    float getLast();
+    #ifdef MBED_OPERATORS
+    /** An operator shorthand for readTemp() to calculate filtered temperature
+     */
+    operator float() {
+        return read();
+    }
+    #endif
+private:
+    AnalogIn _pin;
+    unsigned short * _arr;
+    float _reading;
+    float _multiplier;
+    int _numSamples;
+    float _offset;
+};
+#endif
\ No newline at end of file