soft PWM for Arduino

softPWM.cpp

#include <Arduino.h>

//==================================================
// softPWM クラス
//==================================================
class softPWM {
public:
    using callback_t = void (*)(void);

    void setup(unsigned int period_ms,
               unsigned int duty_ms,
               unsigned long run_ms,
               callback_t on_cb,
               callback_t off_cb);

    void setup(unsigned int period_ms,
               unsigned int duty_ms,
               unsigned long run_ms);

    bool start(void);
    void stop(void);
    bool update(unsigned long now_ms);

private:
    unsigned int period_ms = 0;
    unsigned int duty_ms   = 0;
    unsigned long run_ms   = 0;

    callback_t on_cb  = nullptr;
    callback_t off_cb = nullptr;

    unsigned long last_cycle_ms = 0;
    unsigned long start_ms      = 0;

    bool is_on      = false;
    bool active     = false;
    bool configured = false;
    bool started    = false;
};

//--------------------------------------------------
void softPWM::setup(unsigned int period,
                    unsigned int duty,
                    unsigned long run_time,
                    callback_t on,
                    callback_t off)
{
    if (active) return;

    if (period == 0) period = 1;
    if (duty >= period) duty = period;

    period_ms = period;
    duty_ms   = duty;

    if (run_time == 0) {
        run_ms = 0;
    } else if (run_time <= duty_ms) {
        run_ms = duty_ms;
    } else {
        const unsigned long remain = run_time - duty_ms;
        const unsigned long k =
            (remain + period_ms - 1UL) / period_ms;
        run_ms = k * (unsigned long)period_ms + (unsigned long)duty_ms;
    }

    on_cb  = on;
    off_cb = off;

    configured = true;
}

//--------------------------------------------------
void softPWM::setup(unsigned int period,
                    unsigned int duty,
                    unsigned long run_time)
{
    setup(period, duty, run_time, on_cb, off_cb);
}

//--------------------------------------------------
bool softPWM::start(void)
{
    if (!configured) return false;

    if (active) {
        stop();
    }

    active  = true;
    is_on   = false;
    started = false;

    last_cycle_ms = 0;
    start_ms = 0;

    return true;
}

//--------------------------------------------------
void softPWM::stop(void)
{
    if (!active) return;

    active = false;

    if (is_on && off_cb) {
        off_cb();
    }

    is_on = false;
    started = false;
}

//--------------------------------------------------
bool softPWM::update(unsigned long now_ms)
{
    if (!active) return active;

    if (!started) {
        started = true;
        last_cycle_ms = now_ms;
        start_ms = now_ms;

        if (on_cb) on_cb();
        is_on = true;
        return active;
    }

    if (run_ms > 0 && (now_ms - start_ms) >= run_ms) {
        stop();
        return active;
    }

    const unsigned long elapsed = now_ms - last_cycle_ms;

    if (elapsed >= period_ms) {
        last_cycle_ms = now_ms;

        if (on_cb) on_cb();
        is_on = true;
        return active;
    }

    if (is_on && elapsed >= duty_ms) {
        if (off_cb) off_cb();
        is_on = false;
    }
    return active;
}

//==================================================
// テスト用コード（UNO ビルトインLED）
//==================================================

constexpr int LED_PIN = LED_BUILTIN;

void ledOn()
{
    digitalWrite(LED_PIN, HIGH);
}

void ledOff()
{
    digitalWrite(LED_PIN, LOW);
}

softPWM pwm;

void setup()
{
    pinMode(LED_PIN, OUTPUT);
    digitalWrite(LED_PIN, LOW);

    // 周期 2000ms / duty 300ms / 稼働 8000ms
    pwm.setup(2000, 300, 8000, ledOn, ledOff);

    pwm.start();
    delay(3000);
    ledOn();
    delay(3000);
    ledOff();
    delay(500);
}

void loop()
{
    if (! pwm.update(millis()) ) {
	ledOn();
	delay(2000);
	ledOff();
	delay(1000);
	pwm.setup(500, 250, 0, ledOn, ledOff);
	pwm.start();
    }
}

// # Local Variables:
// # mode: C++
// # End: