pointlights example and presentation for Interactivity course
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enum ledStates {INCREASE, DECREASE, STAY, WAVE, OFF, ON}; // Here we make nicknames for the different states our program supports.
enum ledStates ledState; // We define 'ledState' as type ledStates'
enum ledStates previousLedState = ledState;
unsigned long startMillis; //some global variables available anywhere in the program
unsigned long currentMillis;
int brightness = 0; // our main variable for setting the brightness of the LED
float velocity = 1.0; // the speed at which we change the brightness.
int ledPin = 9; // we use pin 9 for PWM
int p = 0; // use to keep track how often we plot
int plotFrequency = 3; // how often we plot, every Nth time.
void setup() {
// put your setup code here, to run once:
pinMode(ledPin, OUTPUT); // set ledPin as an output.
Serial.begin(9600); // initiate the Serial monitor so we can use the Serial Plotter to graph our patterns
void loop() {
// put your main code here, to run repeatedly:
analogWrite(ledPin, brightness);
currentMillis = millis(); //store the current time since the program started
void compose() {
// this is a state machine which allows us to decouple the various operations from timed loops.
// instead we just switch from state to state when particular conditions are met.
// we switch states by calling the changeState() function.
switch (ledState){
brightness = increase_brightness(brightness, 1);
plot("INCREASING", brightness);
if (brightness > 250){
//ledState = WAVE;
brightness = decrease_brightness(brightness, 0.5);
plot("DECREASING", brightness);
if (brightness == 0){
case WAVE:
plot("WAVE", brightness);
brightness = sinewave(1000,256,0); // you can tweak the parameters of the sinewave
analogWrite(ledPin, brightness);
if (currentMillis - startMillis >= 5000){ //change state after 5 secs by comparing the time elapsed since we last change state
case STAY:
plot("STAY", brightness);
brightness = brightness;
case ON:
plot("ON", brightness);
brightness = 255;
case OFF:
plot("OFF", brightness);
brightness = 0;
if (currentMillis - startMillis >= 1000){
void changeState(ledStates newState){
// call to change state, will keep track of time since last state
startMillis = millis();
ledState = newState;
void plot(char *state, int brightness){
// use this function to plot a graph.
// it will normalize the auto-scaling plotter
if ((p % plotFrequency) == 0){
Serial.print(", ");
Serial.println(", 0, 300");
int increase_brightness (int brightness, float velocity){
return brightness = brightness + 1 * velocity;
int decrease_brightness (int brightness, float velocity){
return brightness = brightness - 1 * velocity;
int sinewave(float duration, float amplitude, int offset){
// Generate a sine oscillation, return a number.
// In case you are using this for analogWrite, make sure the amplitude does not exceed 256
float period = millis()/duration; // Duration in ms determines the wavelength.
float midpoint = amplitude / 2; // set the midpoint of the wave at half the amplitude so there are no negative numbers
int value = midpoint + midpoint * sin ( period * 2.0 * PI );
value = value + offset; //offset allows you to move the wave up and down on the Y-axis. Should not exceed the value of amplitude to prevent clipping.
return value;