Diff: ServoDrive.cpp

Revision:

0:575ce3f4b7ec

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ServoDrive.cpp	Fri Mar 11 10:39:05 2016 +0000
@@ -0,0 +1,112 @@
+/*********************************************************
+*ServoDrive.cpp                                          *
+*Author: Elijah Orr                                      *
+*                                                        *  
+*A library of functions that can be used to control the  * 
+*RenBuggy via a servo motor.                             *
+*********************************************************/
+
+#ifndef SERVODRIVE_C
+#define SERVODRIVE_C
+
+#include "mbed.h"
+#include "ServoDrive.h"
+
+
+/* A pin is configured as PwmOut to output the PWM signal that will
+control the servo. Two pins are configured as DigitalOut to switch
+the drive motors on/off. Information about classes used here can be
+found in the mbed library. */
+PwmOut servo(servoPin);
+DigitalOut Lmotor(LeftMotorPin);
+DigitalOut Rmotor(RightMotorPin);
+
+/* functions to start and stop the drive motors simply set the DigitalOut
+pins to 1 or 0 to switch the motors on/off */
+
+/****************************************************************
+* Function: go()                                                *
+*                                                               *
+* Enables the two drive motors of the RenBuggy                  *
+*                                                               *
+* Inputs: none                                                  *
+*                                                               *
+* Returns: none                                                 *
+****************************************************************/
+extern void go()
+{
+    Lmotor = Rmotor = 1;
+}
+
+/****************************************************************
+* Function: stop()                                              *
+*                                                               *
+* Disables the two drive motors of the RenBuggy                 *
+*                                                               *
+* Inputs: none                                                  *
+*                                                               *
+* Returns: none                                                 *
+****************************************************************/
+extern void stop()
+{
+    Lmotor = Rmotor = 0;
+}
+
+/* a function is set up to configure the PWM output so that it will have the
+correct properties to operate the servo. */
+
+/****************************************************************
+* Function: configurePWM()                                      *
+*                                                               *
+* Configures a PWM signal for controlling the servo             *
+*                                                               *
+* Inputs: Period is the period of the signal in microseconds    *
+* and Pulsewidth is the pulsewidth of the signal in microseconds*                                                   
+*                                                               *
+* Returns: none                                                 *
+****************************************************************/
+extern void configurePWM(int Period, int Pulsewidth)
+{
+    /* classes that set the properties of the PWM signal are passed the variables 
+    Period and Pulsewidth to set the frequency and duty cycle of the signal. */
+    servo.period_us(Period);
+    servo.pulsewidth_us(Pulsewidth);
+}
+
+/* to make the main function easy to write, setDirection will allow a value in 
+degrees to be passed to it, and then do any necessary conversions. angle must be
+a float as the conversion involves non integer values. */
+
+/****************************************************************
+* Function: setDirection()                                      *
+*                                                               *
+* Sets the direction in which the steering servo is pointing    *
+*                                                               *
+* Inputs: A floating point value representing the angle of the  *
+* servo in degrees                                              *                                                   
+*                                                               *
+* Returns: The pulsewith of the signal in microseconds          *
+****************************************************************/
+extern int setDirection(float angle)
+{   
+    /* it is possible to pass numbers outside the operational range of the servo
+    to setDirection, to resolve this there are two checks here. If angle is outside 
+    the boundaries it will be set to either the maximum or minimum value. */
+    if(angle < 0)
+    {
+        angle = 0;
+    }
+    if(angle > 90)
+    {
+        angle = 90;
+    }
+    /* to properly control the servo, the pulsewidth must be between 1000 and 2000 
+    micro seconds, so a simple conversion is used to translate the angle into a value
+    within these bounds. The new value is stored in the variable pulse. */
+    int pulse = 1000 + ((angle/90)*1000);
+    servo.pulsewidth_us(pulse); 
+    
+    return pulse;
+}
+
+#endif //SERVODRIVE_C
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