PwmOut.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
00020  * SOFTWARE.
00021  */
00022 #ifndef MBED_PWMOUT_H
00023 #define MBED_PWMOUT_H
00024 
00025 #include "platform.h"
00026 
00027 #if DEVICE_PWMOUT
00028 #include "pwmout_api.h"
00029 
00030 namespace mbed {
00031 
00032 /** A pulse-width modulation digital output
00033  *
00034  * Example
00035  * @code
00036  * // Fade a led on.
00037  * #include "mbed.h"
00038  *
00039  * PwmOut led(LED1);
00040  *
00041  * int main() {
00042  *     while(1) {
00043  *         led = led + 0.01;
00044  *         wait(0.2);
00045  *         if(led == 1.0) {
00046  *             led = 0;
00047  *         }
00048  *     }
00049  * }
00050  * @endcode
00051  *
00052  * @note
00053  *  On the LPC1768 and LPC2368, the PWMs all share the same
00054  *  period - if you change the period for one, you change it for all.
00055  *  Although routines that change the period maintain the duty cycle
00056  *  for its PWM, all other PWMs will require their duty cycle to be
00057  *  refreshed.
00058  */
00059 class PwmOut {
00060 
00061 public:
00062 
00063     /** Create a PwmOut connected to the specified pin
00064      *
00065      *  @param pin PwmOut pin to connect to
00066      */
00067     PwmOut(PinName pin) {
00068         pwmout_init(&_pwm, pin);
00069     }
00070 
00071     /** Set the ouput duty-cycle, specified as a percentage (float)
00072      *
00073      *  @param value A floating-point value representing the output duty-cycle,
00074      *    specified as a percentage. The value should lie between
00075      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00076      *    Values outside this range will be saturated to 0.0f or 1.0f.
00077      */
00078     void write(float value) {
00079         pwmout_write(&_pwm, value);
00080     }
00081 
00082     /** Return the current output duty-cycle setting, measured as a percentage (float)
00083      *
00084      *  @returns
00085      *    A floating-point value representing the current duty-cycle being output on the pin,
00086      *    measured as a percentage. The returned value will lie between
00087      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00088      *
00089      *  @note
00090      *  This value may not match exactly the value set by a previous <write>.
00091      */
00092     float read() {
00093         return pwmout_read(&_pwm);
00094     }
00095 
00096     /** Set the PWM period, specified in seconds (float), keeping the duty cycle the same.
00097      *
00098      *  @note
00099      *   The resolution is currently in microseconds; periods smaller than this
00100      *   will be set to zero.
00101      */
00102     void period(float seconds) {
00103         pwmout_period(&_pwm, seconds);
00104     }
00105 
00106     /** Set the PWM period, specified in milli-seconds (int), keeping the duty cycle the same.
00107      */
00108     void period_ms(int ms) {
00109         pwmout_period_ms(&_pwm, ms);
00110     }
00111 
00112     /** Set the PWM period, specified in micro-seconds (int), keeping the duty cycle the same.
00113      */
00114     void period_us(int us) {
00115         pwmout_period_us(&_pwm, us);
00116     }
00117 
00118     /** Set the PWM pulsewidth, specified in seconds (float), keeping the period the same.
00119      */
00120     void pulsewidth(float seconds) {
00121         pwmout_pulsewidth(&_pwm, seconds);
00122     }
00123 
00124     /** Set the PWM pulsewidth, specified in milli-seconds (int), keeping the period the same.
00125      */
00126     void pulsewidth_ms(int ms) {
00127         pwmout_pulsewidth_ms(&_pwm, ms);
00128     }
00129 
00130     /** Set the PWM pulsewidth, specified in micro-seconds (int), keeping the period the same.
00131      */
00132     void pulsewidth_us(int us) {
00133         pwmout_pulsewidth_us(&_pwm, us);
00134     }
00135 
00136 #ifdef MBED_OPERATORS
00137     /** A operator shorthand for write()
00138      */
00139     PwmOut& operator= (float value) {
00140         write(value);
00141         return *this;
00142     }
00143 
00144     PwmOut& operator= (PwmOut& rhs) {
00145         write(rhs.read());
00146         return *this;
00147     }
00148 
00149     /** An operator shorthand for read()
00150      */
00151     operator float() {
00152         return read();
00153     }
00154 #endif
00155 
00156 protected:
00157     pwmout_t _pwm;
00158 };
00159 
00160 } // namespace mbed
00161 
00162 #endif
00163 
00164 #endif
00165