Diff: SHARPIR.cpp

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0:323d66022af5

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+++ b/SHARPIR.cpp	Mon Aug 02 12:38:00 2010 +0000
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+/* mbed SHARPIR distance sensor
+ * Copyright (c) 2010 Tomas Johansen
+ *
+ * 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.
+ */
+
+
+#include "mbed.h"
+#include "SHARPIR.h"
+
+
+/* This function is currently only working for the Sharp GP2Y0A02YK0F sensor
+ * which measures from around 20cm to 150cm. To adapt this to other Sharp IR 
+ * sensors, you have to calculate the variables reg and exp.
+ * 
+ * To quickly calculate reg and exp, use microsoft excel to plot the graph 
+ * provided in the datasheet. You should create a scatterplot (except that 
+ * the y-axis is [cm], and x-axis is [V]).
+ *
+ * When you get the values, right click the line in the graph and select 
+ * "Add Trendline". Select "power". Also, in the trendline options, check 
+ * that you want to see the function. It will then be printed in your 
+ * scatterplot.
+ *
+ * This is the function: Reg*x^exp.
+ *
+ *
+ * Example:
+ *
+ * SHARPIR sensor(p20);
+ * sensor.calibrate(57.373, 1.3166, 0.45, 2.5);
+ * while(1){
+ *     serial.printf("cm: %f ", sensor.cm()); 
+ *     wait_ms(50);
+ * }
+ *
+ * You can also use this method to manually plot values you've measured with 
+ * the "volt" function, which in the end should give a result similar to the 
+ * values provided below.
+ *
+ * Feel free to contact me with improvements for the source code, and
+ * especially for values that would work for other sensors.
+ */
+
+
+SHARPIR::SHARPIR(PinName AnalogPort)
+        : _analogin(AnalogPort) {
+    higherrange=2.5;
+    lowerrange=0.45;
+    reg=57.373; //60.495
+    exp=-1.3166; //-1.1904
+}
+
+void calibrate(double reg, float exp, double lowerrange, double higherrange) { //sets new reg and exp value
+}
+
+float SHARPIR::volt() {
+    return(_analogin.read()*3.3); //analogin function returns a percentage which describes how much of 3.3v it's reading, therefor multiply it by 3,3 to get the correct analogin voltage.
+}
+
+float SHARPIR::cm() {
+    float v;
+    v=volt();
+    if (v>higherrange) //sensor is out of higher range
+        return(0);
+    else if (v<lowerrange)
+        return(-1.0); //sensor is out of lower range
+    else
+        return(reg*pow(v, exp));
+}
+
+float SHARPIR::inch() {
+    float v;
+    v=volt();
+    if (v>higherrange) //sensor is out of higher range
+        return(0);
+    else if (v<lowerrange)
+        return(-1.0); //sensor is out of range
+    else
+        return(0.393700787*reg*pow(v, exp));
+}
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