PwmOut.h

00001 /* mbed Microcontroller Library - PwmOut
00002  * Copyright (c) 2007-2011 ARM Limited. All rights reserved.
00003  */ 
00004  
00005 #ifndef MBED_PWMOUT_H
00006 #define MBED_PWMOUT_H
00007 
00008 #include "device.h"
00009 
00010 #if DEVICE_PWMOUT
00011 
00012 #include "platform.h"
00013 #include "PinNames.h"
00014 #include "PeripheralNames.h"
00015 #include "Base.h"
00016 
00017 namespace mbed {
00018 
00019 /** A pulse-width modulation digital output
00020  *
00021  * Example
00022  * @code
00023  * // Fade a led on.
00024  * #include "mbed.h"
00025  *
00026  * PwmOut led(LED1);
00027  * 
00028  * int main() {
00029  *     while(1) {
00030  *         led = led + 0.01;
00031  *         wait(0.2);
00032  *         if(led == 1.0) {
00033  *             led = 0;
00034  *         }
00035  *     }
00036  * }
00037  * @endcode
00038  *
00039  * @note
00040  *  On the LPC1768 and LPC2368, the PWMs all share the same
00041  *  period - if you change the period for one, you change it for all.
00042  *  Although routines that change the period maintain the duty cycle
00043  *  for its PWM, all other PWMs will require their duty cycle to be
00044  *  refreshed.
00045  */
00046 class PwmOut : public Base {
00047 
00048 public:
00049 
00050     /** Create a PwmOut connected to the specified pin
00051      *
00052      *  @param pin PwmOut pin to connect to
00053      */
00054     PwmOut(PinName pin, const char *name = NULL);
00055 
00056     /** Set the ouput duty-cycle, specified as a percentage (float)
00057      *
00058      *  @param value A floating-point value representing the output duty-cycle, 
00059      *    specified as a percentage. The value should lie between
00060      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00061      *    Values outside this range will be saturated to 0.0f or 1.0f.     
00062      */
00063     void write(float value);
00064 
00065     /** Return the current output duty-cycle setting, measured as a percentage (float)
00066      *
00067      *  @returns
00068      *    A floating-point value representing the current duty-cycle being output on the pin, 
00069      *    measured as a percentage. The returned value will lie between
00070      *    0.0f (representing on 0%) and 1.0f (representing on 100%).
00071      *
00072      *  @note
00073      *    This value may not match exactly the value set by a previous <write>.
00074      */
00075     float read();
00076     
00077     /** Set the PWM period, specified in seconds (float), keeping the duty cycle the same.
00078      *
00079      *  @note
00080      *    The resolution is currently in microseconds; periods smaller than this
00081      *    will be set to zero.
00082      */
00083     void period(float seconds);
00084 
00085     /** Set the PWM period, specified in milli-seconds (int), keeping the duty cycle the same.
00086      */
00087     void period_ms(int ms);
00088 
00089     /** Set the PWM period, specified in micro-seconds (int), keeping the duty cycle the same.
00090      */
00091     void period_us(int us);
00092 
00093     /** Set the PWM pulsewidth, specified in seconds (float), keeping the period the same.
00094      */
00095     void pulsewidth(float seconds);
00096 
00097     /** Set the PWM pulsewidth, specified in milli-seconds (int), keeping the period the same.
00098      */
00099     void pulsewidth_ms(int ms);
00100 
00101     /** Set the PWM pulsewidth, specified in micro-seconds (int), keeping the period the same.
00102      */
00103     void pulsewidth_us(int us);
00104 
00105 #ifdef MBED_OPERATORS
00106     /** A operator shorthand for write()
00107      */
00108     PwmOut& operator= (float value);
00109     PwmOut& operator= (PwmOut& rhs);
00110 
00111     /** An operator shorthand for read()
00112      */
00113     operator float();
00114 #endif
00115 
00116 #ifdef MBED_RPC
00117     virtual const struct rpc_method *get_rpc_methods();
00118     static struct rpc_class *get_rpc_class();
00119 #endif
00120 
00121 protected:
00122 
00123     PWMName _pwm;
00124 
00125 };
00126 
00127 } // namespace mbed
00128 
00129 #endif
00130 
00131 #endif