continuous rotation servo demonstrates a different approach of using PWM.
A continuous rotation servo is a standard servo modified in 2 ways. First the "position feedback" in the servo is disconnected and set to always read as if the servo was in the center position. Second the "stop" which physically prevents the motor from turning 360 degrees is removed.
Then if you set the servo to 0 degrees it rotates fast in one direction if you set it 180 degrees it move in the opposite direction.
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