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SharpIR.cpp

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+/*
+	SharpIR
+
+	Arduino library for retrieving distance (in cm) from the analog GP2Y0A21Y and GP2Y0A02YK
+
+	From an original version of Dr. Marcal Casas-Cartagena (marcal.casas@gmail.com)     
+
+    Version : 1.0 : Guillaume Rico
+    + Remove average and use median
+    + Definition of number of sample in .h
+    + Define IR pin as input
+
+    Version : 1.1 : Thibaut Mauon
+    + Add SHARP GP2Y0A710K0F for 100cm to 500cm by Thibaut Mauron
+
+	https://github.com/guillaume-rico/SharpIR
+
+    Original comment from Dr. Marcal Casas-Cartagena :
+   The Sahrp IR sensors are cheap but somehow unreliable. I've found that when doing continous readings to a
+   fix object, the distance given oscilates quite a bit from time to time. For example I had an object at
+   31 cm. The readings from the sensor were mainly steady at the correct distance but eventually the distance
+   given dropped down to 25 cm or even 16 cm. That's quite a bit and for some applications it is quite
+   unacceptable. I checked the library http://code.google.com/p/gp2y0a21yk-library/ by Jeroen Doggen
+   (jeroendoggen@gmail.com) and what the author was doing is to take a bunch of readings and give an average of them
+
+   The present library works similary. It reads a bunch of readings (avg), it checks if the current reading
+   differs a lot from the previous one (tolerance) and if it doesn't differ a lot, it takes it into account
+   for the mean distance.
+   The distance is calculated from a formula extracted from the graphs on the sensors datasheets
+   After some tests, I think that a set of 20 to 25 readings is more than enough to get an accurate distance
+   Reading 25 times and return a mean distance takes 53 ms. For my application of the sensor is fast enough.
+   This library has the formulas to work with the GP2Y0A21Y and the GP2Y0A02YK sensors but exanding it for
+   other sensors is easy enough.
+*/
+
+#ifdef Arduino
+  #include "Arduino.h"
+#elif defined(SPARK)
+  #include "Particle.h"
+  #include "math.h"
+#endif
+#include "SharpIR.h"
+
+// Initialisation function
+//  + irPin : is obviously the pin where the IR sensor is attached
+//  + sensorModel is an int to differentiate the two sensor models this library currently supports:
+//    > 1080 is the int for the GP2Y0A21Y and 
+//    > 20150 is the int for GP2Y0A02YK and 
+//    > 100500 is the long for GP2Y0A710K0F
+//    The numbers reflect the distance range they are designed for (in cm)
+SharpIR::SharpIR(int irPin, long sensorModel) {
+
+    _irPin=irPin;
+    _model=sensorModel;
+
+    // Define pin as Input
+    pinMode (_irPin, INPUT);
+
+    #ifdef ARDUINO
+      analogReference(DEFAULT);
+    #endif
+}
+
+// Sort an array
+void SharpIR::sort(int a[], int size) {
+    for(int i=0; i<(size-1); i++) {
+        bool flag = true;
+        for(int o=0; o<(size-(i+1)); o++) {
+            if(a[o] > a[o+1]) {
+                int t = a[o];
+                a[o] = a[o+1];
+                a[o+1] = t;
+                flag = false;
+            }
+        }
+        if (flag) break;
+    }
+}
+
+// Read distance and compute it
+float SharpIR::distance() {
+
+    int ir_val[NB_SAMPLE];
+    int distanceCM;
+    float distanceMM;
+    //int distanceMicro;
+    float voltage;
+    float current;
+
+
+    for (int i=0; i<NB_SAMPLE; i++){
+        // Read analog value
+        ir_val[i] = analogRead(_irPin);
+    }
+
+    // Sort it 
+    sort(ir_val,NB_SAMPLE);
+
+    voltage = map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0;
+    if (_model==1080) {
+
+        // Different expressions required as the Photon has 12 bit ADCs vs 10 bit for Arduinos
+        #ifdef ARDUINO
+          //FIX THE REST OF THESE NUMBERS (ONLY 2A IS RIGHT)
+          //DEFAULT: 
+          //distanceCM = 27.728 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.2045);
+          //SENSOR1:
+          //distanceCM = 17.077 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -0.862);
+          //SENSOR2a:
+          //distanceCM = 27.113 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.142);
+          distanceMM = 271.24 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.144);
+          //distanceMicro = 271130 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.142);
+          //SENSOR2b:
+          //distanceCM = 18.374 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -0.88);
+          //SENSOR3:
+          //distanceCM = 17.621 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -0.869);
+          //SENSOR4:
+          //distanceCM = 18.096 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -0.881);
+
+        #elif defined(SPARK)
+          distanceCM = 27.728 * pow(map(ir_val[NB_SAMPLE / 2], 0, 4095, 0, 5000)/1000.0, -1.2045);
+        #endif
+
+    } else if (_model==20150){
+
+        // Previous formula used by  Dr. Marcal Casas-Cartagena
+        // puntualDistance=61.573*pow(voltFromRaw/1000, -1.1068);
+
+        // Different expressions required as the Photon has 12 bit ADCs vs 10 bit for Arduinos
+        #ifdef ARDUINO
+          distanceCM = 60.374 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.16);
+        #elif defined(SPARK)
+          distanceCM = 60.374 * pow(map(ir_val[NB_SAMPLE / 2], 0, 4095, 0, 5000)/1000.0, -1.16);
+        #endif
+
+    } else if (_model==430){
+
+        // Different expressions required as the Photon has 12 bit ADCs vs 10 bit for Arduinos
+        #ifdef ARDUINO
+          distanceCM = 12.08 * pow(map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000)/1000.0, -1.058);
+        #elif defined(SPARK)
+          distanceCM = 12.08 * pow(map(ir_val[NB_SAMPLE / 2], 0, 4095, 0, 5000)/1000.0, -1.058);
+        #endif
+
+    } else if (_model==100500){
+
+        #ifdef ARDUINO
+          current = map(ir_val[NB_SAMPLE / 2], 0, 1023, 0, 5000);
+        #elif defined(SPARK)
+          current = map(ir_val[NB_SAMPLE / 2], 0, 4095, 0, 5000);
+        #endif
+        // use the inverse number of distance like in the datasheet (1/L)
+        // y = mx + b = 137500*x + 1125 
+        // x = (y - 1125) / 137500
+        // Different expressions required as the Photon has 12 bit ADCs vs 10 bit for Arduinos
+        if (current < 1400 || current > 3300) {
+          //false data
+          distanceCM = 0;
+        } else {
+          distanceCM = 1.0 / (((current - 1125.0) / 1000.0) / 137.5);
+        }
+    }
+    return distanceMM;
+}
+
+
+
+

SharpIR.h

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+/*
+	SharpIR
+
+	Arduino library for retrieving distance (in cm) from the analog GP2Y0A21Y and GP2Y0A02YK
+
+	From an original version of Dr. Marcal Casas-Cartagena (marcal.casas@gmail.com)     
+
+    Version : 1.0 : Guillaume Rico
+
+	https://github.com/guillaume-rico/SharpIR
+
+*/
+
+#ifndef SharpIR_h
+#define SharpIR_h
+
+#define NB_SAMPLE 25
+
+#ifdef ARDUINO
+  #include "Arduino.h"
+#elif defined(SPARK)
+  #include "Particle.h"
+#endif
+
+class SharpIR
+{
+  public:
+
+    SharpIR (int irPin, long sensorModel);
+    float distance();
+
+  private:
+
+    void sort(int a[], int size);
+
+    int _irPin;
+    long _model;
+};
+
+#endif

sharp_ir_sensor_mmsensing.ino

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+/*SHARP GP2Y0A21YK0F IR distance sensor with Arduino and SharpIR library example code. More info: https://www.makerguides.com */
+
+// Include the library:
+#include <SharpIR.h>
+
+// Define model and inpu pin:
+#define IRPin A0
+#define model 1080
+
+// Create variable to store the distance:
+int distance_cm;
+double distance_mm;
+
+/* Model :
+  GP2Y0A02YK0F --> 20150
+  GP2Y0A21YK0F --> 1080
+  GP2Y0A710K0F --> 100500
+  GP2YA41SK0F --> 430
+*/
+
+// Create a new instance of the SharpIR class:
+SharpIR mySensor = SharpIR(IRPin, model);
+
+void setup() {
+  // Begin serial communication at a baudrate of 9600:
+  Serial.begin(9600);
+
+}
+
+void loop() {
+  // Get a distance measurement and store it as distance_cm:
+  distance_mm = mySensor.distance();
+
+  // Print the measured distance to the serial monitor:
+
+  Serial.print("Mean distance: ");
+  Serial.print(distance_mm);
+  Serial.println(" mm");
+
+  delay(1000);
+}