PwmOut.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #ifndef MBED_PWMOUT_H
00017 #define MBED_PWMOUT_H
00018 
00019 #include "platform.h"
00020 
00021 #if DEVICE_PWMOUT
00022 #include "pwmout_api.h"
00023 #include "critical.h"
00024 
00025 namespace mbed {
00026 
00027 /** A pulse-width modulation digital output
00028  *
00029  * @Note Synchronization level: Interrupt safe
00030  *
00031  * Example
00032  * @code
00033  * // Fade a led on.
00034  * #include "mbed.h"
00035  *
00036  * PwmOut led(LED1);
00037  *
00038  * int main() {
00039  *     while(1) {
00040  *         led = led + 0.01;
00041  *         wait(0.2);
00042  *         if(led == 1.0) {
00043  *             led = 0;
00044  *         }
00045  *     }
00046  * }
00047  * @endcode
00048  *
00049  * @note
00050  *  On the LPC1768 and LPC2368, the PWMs all share the same
00051  *  period - if you change the period for one, you change it for all.
00052  *  Although routines that change the period maintain the duty cycle
00053  *  for its PWM, all other PWMs will require their duty cycle to be
00054  *  refreshed.
00055  */
00056 class PwmOut {
00057 
00058 public:
00059 
00060     /** Create a PwmOut connected to the specified pin
00061      *
00062      *  @param pin PwmOut pin to connect to
00063      */
00064     PwmOut(PinName pin) {
00065         core_util_critical_section_enter();
00066         pwmout_init(&_pwm, pin);
00067         core_util_critical_section_exit();
00068     }
00069 
00070     /** Set the ouput duty-cycle, specified as a percentage (float)
00071      *
00072      *  @param value A floating-point value representing the output duty-cycle,
00073      *    specified as a percentage. The value should lie between
00074      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00075      *    Values outside this range will be saturated to 0.0f or 1.0f.
00076      */
00077     void write(float value) {
00078         core_util_critical_section_enter();
00079         pwmout_write(&_pwm, value);
00080         core_util_critical_section_exit();
00081     }
00082 
00083     /** Return the current output duty-cycle setting, measured as a percentage (float)
00084      *
00085      *  @returns
00086      *    A floating-point value representing the current duty-cycle being output on the pin,
00087      *    measured as a percentage. The returned value will lie between
00088      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00089      *
00090      *  @note
00091      *  This value may not match exactly the value set by a previous <write>.
00092      */
00093     float read() {
00094         core_util_critical_section_enter();
00095         float val = pwmout_read(&_pwm);
00096         core_util_critical_section_exit();
00097         return val;
00098     }
00099 
00100     /** Set the PWM period, specified in seconds (float), keeping the duty cycle the same.
00101      *
00102      *  @note
00103      *   The resolution is currently in microseconds; periods smaller than this
00104      *   will be set to zero.
00105      */
00106     void period(float seconds) {
00107         core_util_critical_section_enter();
00108         pwmout_period(&_pwm, seconds);
00109         core_util_critical_section_exit();
00110     }
00111 
00112     /** Set the PWM period, specified in milli-seconds (int), keeping the duty cycle the same.
00113      */
00114     void period_ms(int ms) {
00115         core_util_critical_section_enter();
00116         pwmout_period_ms(&_pwm, ms);
00117         core_util_critical_section_exit();
00118     }
00119 
00120     /** Set the PWM period, specified in micro-seconds (int), keeping the duty cycle the same.
00121      */
00122     void period_us(int us) {
00123         core_util_critical_section_enter();
00124         pwmout_period_us(&_pwm, us);
00125         core_util_critical_section_exit();
00126     }
00127 
00128     /** Set the PWM pulsewidth, specified in seconds (float), keeping the period the same.
00129      */
00130     void pulsewidth(float seconds) {
00131         core_util_critical_section_enter();
00132         pwmout_pulsewidth(&_pwm, seconds);
00133         core_util_critical_section_exit();
00134     }
00135 
00136     /** Set the PWM pulsewidth, specified in milli-seconds (int), keeping the period the same.
00137      */
00138     void pulsewidth_ms(int ms) {
00139         core_util_critical_section_enter();
00140         pwmout_pulsewidth_ms(&_pwm, ms);
00141         core_util_critical_section_exit();
00142     }
00143 
00144     /** Set the PWM pulsewidth, specified in micro-seconds (int), keeping the period the same.
00145      */
00146     void pulsewidth_us(int us) {
00147         core_util_critical_section_enter();
00148         pwmout_pulsewidth_us(&_pwm, us);
00149         core_util_critical_section_exit();
00150     }
00151 
00152     /** A operator shorthand for write()
00153      */
00154     PwmOut& operator= (float value) {
00155         // Underlying call is thread safe
00156         write(value);
00157         return *this;
00158     }
00159 
00160     PwmOut& operator= (PwmOut& rhs) {
00161         // Underlying call is thread safe
00162         write(rhs.read());
00163         return *this;
00164     }
00165 
00166     /** An operator shorthand for read()
00167      */
00168     operator float() {
00169         // Underlying call is thread safe
00170         return read();
00171     }
00172 
00173 protected:
00174     pwmout_t _pwm;
00175 };
00176 
00177 } // namespace mbed
00178 
00179 #endif
00180 
00181 #endif