SoftPdmOut.h

00001 /******************************************************************************************************/
00002 /*  Pulse Density Modulation driver.                                                                  */
00003 /*  FILE: PDM.h                                                                                       */
00004 /*                                                                                                    */
00005 /*  Code based on an article and source code released by Ken Wada from Aurium Technologies Inc.       */
00006 /*  http://www.embedded.com/electronics-blogs/embedded-round-table/4414405/Pulse-density-modulation   */
00007 /*                                                                                                    */
00008 /******************************************************************************************************/
00009 
00010 #ifndef   __PDM_BB_H
00011 #define   __PDM_BB_H
00012 
00013 #include "mbed.h"
00014 
00015 /** Class to use software defined Pulse Density Modulation (PDM).
00016 *
00017 * 'pdm' pin can be any digital pin.
00018 * 
00019 \code
00020 //Example
00021 //-------
00022 #include "mbed.h"
00023 #include "SoftPdmOut.h"
00024 
00025 SoftPdmOut pdm(LED1);
00026 
00027 int main()
00028 {
00029     float pdmSet = 0.0f;
00030     float pdmAdd = 0.01f;
00031 
00032     // Continuously cycle the output
00033     while(1)
00034     {
00035         pdm = pdmSet;
00036         wait_ms(10);
00037         if(pdmSet >= 1.0f)
00038             pdmAdd = -0.01f;
00039         if(pdmSet <= 0.0f)
00040             pdmAdd = 0.01f;
00041         pdmSet += pdmAdd;
00042     }
00043 }
00044 \endcode
00045 */ 
00046 
00047 class SoftPdmOut {
00048 public:
00049     /** Create a PDM object connected to a digital pin.
00050     *
00051     * @param pdm        : Digital pin.
00052     * @param PulseWidth : Optional - The desired pulse width in microseconds (default = 500us).
00053     * @param Dmax       : Optional - This is the total number of states in the DAC output (default = 64).
00054     * @param StartLevel : Optional - The DAC percentage (0.0 to 1.0) to be preprogrammed upon initialization (default = 0).
00055     * @return none
00056     */
00057     SoftPdmOut(PinName pdm, uint32_t PulseWidth = 500, uint32_t Dmax = 64, float StartLevel = 0);
00058 
00059     /** Start the PDM.
00060     * @param none
00061     * @return none
00062     */
00063     void start(void);
00064 
00065     /** Stop the PDM.
00066     * @param idleState (optional, allows the user to define the idle state - default = 0)
00067     * @return none
00068     */
00069     void stop(bool idleState = 0);
00070 
00071     /** Change the pulse width.
00072     * @param level : The desired pulse width in microseconds.
00073     * @return none
00074     */
00075     void PulseWidth(uint32_t level);
00076 
00077     /** Read the pulse width.
00078     * @param none.
00079     * @return current PulseWidth value
00080     */
00081     uint32_t getPulseWidth(void);
00082 
00083     /** Change the total number of states in the DAC output (DMAX).
00084     * @param level : The desired max. level.
00085     * @return none.
00086     */
00087     void Dmax(uint32_t level);
00088 
00089     /** Read the total number of states in the DAC output (DMAX).
00090     * @param none.
00091     * @return current DMAX value.
00092     */
00093     uint32_t getDmax(void);
00094 
00095     /** Set the PDM level, specified as a percentage (float).
00096     * @param level
00097     * @return none
00098     */
00099     void write(float level);
00100 
00101     /** Return the current PDM level as a percentage (float).
00102     * @param none
00103     * @return level
00104     */
00105     float read(void);
00106 
00107     /**
00108     * An operator shorthand for read()
00109     */
00110     operator float();
00111 
00112     /**
00113     * An operator shorthand for write()
00114     */
00115     SoftPdmOut& operator= (float value);
00116 
00117 private:
00118     Ticker _pdmTicker;
00119     DigitalOut _pdm;
00120     uint32_t _PulseWidth;
00121     uint32_t _Level;
00122     uint32_t _Dmax;
00123     uint32_t _accumulator;
00124     bool _running;
00125     void pdmTick(void);
00126 };
00127 #endif