Liyang HU / Pulsator Featured

Use the hardware PwmOut to pulsate an LED (or something else), with selectable active high/low, customisable intensity function, gamma correction, and number of brightness levels.

Dependents:   RedButton

Pulsator.cpp

Committer:
huliyang
Date:
2015-04-24
Revision:
0:dda7f6f55dc1
Child:
1:bcddb9898625

File content as of revision 0:dda7f6f55dc1:

#include <math.h>
#include <mbed.h>

#include <Pulsator.h>

#ifndef M_PI
# define M_PI    3.14159265358979323846
#endif

#ifndef M_PI_2
# define M_PI_2  1.57079632679489661923
#endif

void Pulsator::step(void)
{
    // sinf(phase_2)^2 == (1 - cosf(phase)) / 2
    float s = sinf(phase_2);
    float level = powf(s * s, gamma);
    out = active_high ? level : 1.0 - level;
    phase_2 += M_PI_2 / (float)(levels - 1);
    if(phase_2 >= M_PI)
        phase_2 = 0.0;
}

void Pulsator::enable(void)
{
    out.period(1.0 / 1024.0);
    phase_2 = 0.0;
    step();
    ticker.attach(this, &Pulsator::step, 0.5 * period / levels);
}

void Pulsator::disable(void)
{
    ticker.detach();
    out = active_high ? 0.0 : 1.0;
}

Pulsator::Pulsator(PinName pin, float period, bool active_high, float gamma, int levels)
    : out(pin), period(period), active_high(active_high), gamma(gamma), levels(levels)
{
    disable();
}

Pulsator& Pulsator::operator=(bool state)
{
    state ? enable() : disable();
    return *this;
}