Software PDM

                         1
max. frequency = -----------------
                 PulseWidth x DMAX

Example
-------
pulse width = 10us
DMAX        = 256 counts

                       1
max. frequency = ------------- = 390.625Hz
                 0.00001 x 256

// mbed-shiny
#include "mbed.h"
#include "SoftPdmOut.h"

SoftPdmOut pdm(LED1);

int main()
{
    float pdmSet = 0.0f;
    float pdmAdd = 0.01f;

    // Continuously cycle the output
    while(1)
    {
        pdm = pdmSet;
        wait_ms(10);
        if(pdmSet >= 1.0f)
            pdmAdd = -0.01f;
        if(pdmSet <= 0.0f)
            pdmAdd = 0.01f;
        pdmSet += pdmAdd;
    }
}

#include "mbed.h"
#include "SoftPdmOut.h"

Serial pc(USBTX, USBRX);

// optional parameters, when omitted, their default library value will be used.
#define PULSEWIDTH 100
#define DMAX       64
#define STARTLEVEL 0.5f

// PinName and optional pulse width, dmax, start level
// When  SoftPdmOut pdm(LED1);  is used, all optional parameters revert to their default values (defined in the library).
SoftPdmOut pdm(LED1, PULSEWIDTH, DMAX, STARTLEVEL);

int main()
{
    pc.baud (38400);
    
    float pdmVal;
    
    printf("PDM test\r\n");
    pdmVal = 0.1f;

    // Stop the PDM with pin idle value = 0
    printf("Stop the PDM with pin idle value = 0\r\n");
    pdm.stop(0);
    wait(1);
    pdm.start();

    // Stop the PDM with pin idle value = 1
    printf("Stop the PDM with pin idle value = 1\r\n");
    pdm.stop(1);
    wait(1);
    pdm.start();

    // Set PDM level, read it back and print it, can be done in two ways :
    // using pdm.write(nn) and pdm.read(nn)  OR  pdm = nn and <variable> = pdm.
    printf("Set the current PDM level to %f\r\n", pdmVal);
    // Write the current PDM level using pdm.write()
    pdm.write(pdmVal);
    // Write the current PDM level using the shorthand notation instead of pdm.write()
    pdm = pdmVal;
    printf("Get the current PDM level : %f\r\n", pdm.read());
    // Read the current PDM level using the shorthand notation instead of pdm.read()
    float dummy = pdm;
    printf("Get the current PDM level : %f\r\n", dummy);
    wait(1);
    // Change the pulse width and DMAX values.
    pdm.PulseWidth(100);
    pdm.Dmax(128);

    float pdmSet = 0.0f;
    float pdmAdd = 0.01f;

    // Cycle the output
    while(1)
    {
        pdm = pdmSet;
        wait_ms(10);
        if(pdmSet >= 1.0f)
            pdmAdd = -0.01f;
        if(pdmSet <= 0.0f)
            pdmAdd = 0.01f;
        pdmSet += pdmAdd;
    }
}