PwmControl.setPwm()

[AlecHub]

The SDK doesn't seem to provide an api, say PwmControl.setPwm(), to be able to specify an exact pwm pusle width.

The following technique seems to work though:

    boolean setPwm(Servo servo, double usPwm)
    {
        if (usPwm >= 500.0 && usPwm <= 2500.00) {
            if (PwmControl.class.isInstance(servo)) {
                PwmControl pwm = (PwmControl) servo;
                PwmControl.PwmRange range = pwm.getPwmRange();
                pwm.setPwmRange(new PwmControl.PwmRange(usPwm, usPwm, range.usFrame));
                servo.setPosition(1.0);
                return true;
            }
        }
        return false;
    }

Would this technique be reliable?

[alan412]

With an oscilloscope, I have verified that this is close to being true for the entire range of 500 to 2500 us.

[alan412]

Playing with it, this small change seems to make it more accurate (but I am not sure why it should from looking at the internal code) -
pwm.setPwmRange(new PwmControl.PwmRange(500, usPwm, range.usFrame));

[AlecHub]

Thank you Alan, and thank you for your book. I especially like the dedication page and your pitch for OpMode.

[AlecHub]

The technique is not 100% effective.

Invoking setPostition() twice seems to be an effective workaround:

    boolean setPwm(Servo servo, double usPwm)
    {
        if (usPwm >= 500.0 && usPwm <= 2500.0) {
            if (PwmControl.class.isInstance(servo)) {
                PwmControl pwm = (PwmControl) servo;
                PwmControl.PwmRange range = pwm.getPwmRange();
                pwm.setPwmRange(new PwmControl.PwmRange(usPwm, usPwm, range.usFrame));

                servo.setPosition(0.0);  // Not 100% effective
                servo.setPosition(1.0);  // Workaround

                return true;
            }
        }
        return false;
    }

The underlying bug could be the cause of other types of intermittent failures.

[AlecHub]

Fyi, this is not effective:

servo.setPosition(1.0);
servo.setPosition(1.0);

Which led me to believe that this would be effective:

// servo.setPosition(0.0);  // Not 100% effective
// servo.setPosition(1.0);  // Workaround

servo.setPosition(++counter % 2);  // Workaround with only one invocation of setPosition()

Indeed it is effective.

However, I'm wondering why a single invocation of setPosition(1.0) per my original post works more often than not.