Diff: main.cpp

Revision:

0:575ce3f4b7ec

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Mar 11 10:39:05 2016 +0000
@@ -0,0 +1,117 @@
+/****************************************************************
+* LightSeekingRobot                                             *
+* Author: Elijah Orr                                            *
+*                                                               * 
+* This program uses the values of two analog inputs (LDRs) to   *
+* steer the RenBuggy via a servo motor.                         *
+*****************************************************************/
+
+/* The library ServoDrive is used in this program to control the 
+servo and drive motors. Libraries are a useful tool for creating
+code that can be reused in multiple programs. */
+#include "mbed.h"
+#include "ServoDrive.h"
+
+AnalogIn LDR1(p15);
+AnalogIn LDR2(p16);
+
+/****************************************************************
+* Function: main()                                              *
+*                                                               *
+* Steers a servo controlled wheel of the Renbuggy according to  *
+* the relative light levels of two LDRs                         *
+*                                                               *
+* Inputs: none                                                  *
+*                                                               *
+* Returns: none                                                 *
+****************************************************************/
+int main()
+{
+    /* variables that will be used in the main are declared */
+    float angle;
+    float LDR1value;
+    float LDR2value;
+    int i;
+    
+    /* these variables are initialised values to be used to 
+     control certain behaviors of the buggy. tolerance sets
+     how much the light levels must differ for it to turn,
+     centreValue is the value in degrees that corresponds to
+     the wheel pointing directly forward, and difAdjust is 
+     used make the values of the two LDR inputs more similar */
+    float tolerance = 0.03;
+    int centreValue = 45;
+    float difAdjust = 0.03;
+    
+    /* call the function to set up the PWM signal for the servo */
+    configurePWM(20000, 1500);
+    
+    /* the angle of the servo is initially set to centre it */
+    angle = centreValue;
+    
+    /* start the buggy moving */
+    go();
+    
+    /* opening a for loop without any conditions starts an infinite
+    loop, so that the contained code runs forever */
+    for(;;)
+    {
+        /* the class member function read() in AnalogIn.h reads the
+        voltage of the of the LDR pins into variables as a floating
+        point value between 0.0 and 1.0 */       
+        LDR1value = LDR1.read();
+        LDR2value = LDR2.read();
+        
+        /* LDR2value has difAdjust added to it to make both LDR values
+        similar enough to compare effectively. The value 0.03 stored in
+        difAdjust was chosen by printing the LDR values to console via
+        USB and observing the difference between values (USBSerial.h was 
+        used for this) */
+        LDR2value = LDR2value + difAdjust;
+        
+        /* the behavior of the RenBuggy is defined by a series of if
+        statements. If the conditions in the parentheses are true,
+        then the code in the if statement will run, if not the program
+        moves on. */
+        
+        /* && is known as the logical AND operator. If both operands are 
+        non zero (i.e. true), then the condition will be true. If one LDR
+        value is significantly larger than the other, then angle will 
+        increment (angle++ means that the value of angle will increase
+        by one) */
+        if((LDR1value - LDR2value > tolerance) && (angle < 90)){
+            angle++;
+        }
+        
+        /* if statements can be followed by an optional else if statement, 
+        which will execute when the above if statement is false, and the 
+        else if condition is true. */
+        else if((LDR2value - LDR1value > tolerance) && (angle > 0)){
+             angle--;   /* angle-- means that angle will decrease by one */
+        }
+        
+        /* If the difference between values is within tolerance, point the 
+        wheel straight forward */
+        else if((LDR1value - LDR2value < tolerance) && (LDR2value - LDR1value < tolerance)){
+            angle = centreValue;
+        }
+        
+        /* a for loop is used to create a delay in the program to make it run
+        a little slower, so that the servo position is updated less freqently */
+        for(i=0;i<400000;i++){}
+        
+        /* the function setDirection is called and passed the variable angle to
+        set the servo position to the new value of angle */
+        setDirection(angle);
+    }
+}
+        
+        
+             
+        
+        
+        
+        
+    
+    
+    
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