File content as of revision 0:8926d6546415:

#include "mbed.h"

/**
 * PwmOut for M0
 */
class M0PwmOut {
public:
    M0PwmOut(PinName pwm, float period = 0.001) : pwm(pwm), period(period), duty(0) {
        this->pwm = 0;
    }

    void write(float duty) {
        if (duty <= 0.0) {
            this->duty = 0;
            pwm = 0;
            ticker.detach();
        } else if (duty >= 1.0) {
            this->duty = 1;
            pwm = 1;
            ticker.detach();
        } else {
            this->duty = duty;
            ticker.attach(this, &M0PwmOut::onTicker, period);
        }
    }

    float read() {
        return duty;
    }
    
    void operator=(float value) {
        write(value);
    }

    operator float() {
        return read();
    }
private:
    DigitalOut pwm;
    Ticker ticker;
    Timeout timeout;
    float period;
    float duty;

    void onTicker() {
        this->pwm = 1;
        timeout.attach(this, &M0PwmOut::onTimeout, duty * period);
    }

    void onTimeout() {
        this->pwm = 0;
    }
};

int main () {
    M0PwmOut leds[] = {LED1, LED2, LED3, LED4};

    for (int i = 0; i < 600; i++) {
        for (int j = 0; j < 4; j++)
            leds[j] = ((i + 5 * j) % 31) / 30.0;
        wait(0.2);
    }
    for (int i = 0; i < 4; i++) leds[i] = 0;
}