Arduino-Development / libraries /Adafruit_Circuit_Playground /examples /FidgetSpinner /FidgetSpinner.h
| // Fidget spinner logic. | |
| // This class represents a fidget spinner that can be spun to a specified | |
| // velocity and then over time will slow down and stop. The spinner keeps track | |
| // of its continuous (floating point) position value within the range 0...<10 | |
| // so it can map to CircuitPlayground pixel positions easily.// Author: Tony DiCola | |
| // License: MIT License (https://opensource.org/licenses/MIT) | |
| // Usage: | |
| // - Create an instance of the class (specifying a custom decay value between 0 and 1, | |
| // the lower the decay the faster the spinner slows down). | |
| // - Call spin to start the spinner moving at the specified velocity (in pixels/second). | |
| // - Call getPosition periodically to get the current spinner position given an elapsed | |
| // amount of seconds since the last getPosition call. | |
| class FidgetSpinner { | |
| public: | |
| FidgetSpinner(float decay=0.5): | |
| _position(0.0), _velocity(0.0), _elapsedS(0.0), _decay(decay) | |
| {} | |
| void spin(float velocity) { | |
| // Start the fidget spinner moving at the specified velocity (in pixels/second). | |
| // Over time the spinner will slow down based on its decay value. | |
| _velocity = velocity; | |
| _elapsedS = 0.0; // Reset elapsed time to start the decay from the beginning. | |
| } | |
| float getPosition(float deltaS) { | |
| // Get the fidget spinner's current position after moving for the specified number | |
| // of milliseconds. Returns a continuous value in the range 0...<10. | |
| _elapsedS += deltaS; | |
| // Compute current velocity based on exponential decay of initial | |
| // velocity over the elapsed time (this causes the spinner to | |
| // gradually slow down and mimics the effects of friction). | |
| float currentVelocity = _velocity*pow(_decay, _elapsedS); | |
| // Now move the position based on the current velocity. | |
| _position += currentVelocity*deltaS; | |
| // Finally make sure position is constrained within 0...<10 range. | |
| _position = fmod(_position, 10.0); | |
| if (_position < 0.0) { | |
| // Ensure position is never negative by wrapping back to the | |
| // same pixel position in a positive location. | |
| _position += 10.0; | |
| } | |
| return _position; | |
| } | |
| private: | |
| float _position; | |
| float _velocity; | |
| float _elapsedS; | |
| float _decay; | |
| }; | |