another clone of servo library

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Servo.cpp

00001 
00002 
00003 /* mbed R/C Servo Library
00004  *  
00005  * Copyright (c) 2007-2010 sford, cstyles
00006  *
00007  * Permission is hereby granted, free of charge, to any person obtaining a copy
00008  * of this software and associated documentation files (the "Software"), to deal
00009  * in the Software without restriction, including without limitation the rights
00010  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00011  * copies of the Software, and to permit persons to whom the Software is
00012  * furnished to do so, subject to the following conditions:
00013  *
00014  * The above copyright notice and this permission notice shall be included in
00015  * all copies or substantial portions of the Software.
00016  *
00017  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00018  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00019  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00020  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00021  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00022  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00023  * THE SOFTWARE.
00024  */
00025  
00026 #include "Servo.h"
00027 #include "mbed.h"
00028  
00029 static float clamp(float value, float min, float max) {
00030     if(value < min) {
00031         return min;
00032     } else if(value > max) {
00033         return max;
00034     } else {
00035         return value;
00036     }
00037 }
00038  
00039 Servo::Servo(PinName pin) : _pwm(pin) {
00040     calibrate();
00041     write(0.5);
00042 }
00043  
00044 void Servo::write(float percent) {
00045     float offset = _range * 2.0 * (percent - 0.5);
00046     _pwm.pulsewidth(0.0015 + clamp(offset, -_range, _range));
00047     _p = clamp(percent, 0.0, 1.0);
00048 }
00049  
00050 void Servo::position(float degrees) {
00051     float offset = _range * (degrees / _degrees);
00052     _pwm.pulsewidth(0.0015 + clamp(offset, -_range, _range));
00053 }
00054  
00055 void Servo::calibrate(float range, float degrees) {
00056     _range = range;
00057     _degrees = degrees;
00058 }
00059  
00060 float Servo::read() {
00061     return _p;
00062 }
00063  
00064 Servo& Servo::operator= (float percent) { 
00065     write(percent);
00066     return *this;
00067 }
00068  
00069 Servo& Servo::operator= (Servo& rhs) {
00070     write(rhs.read());
00071     return *this;
00072 }
00073  
00074 Servo::operator float() {
00075     return read();
00076 }
00077