Servo.cpp

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